Linux: Redis

Last-Modified 是 HttpHeader 中的资源的最后修改时间，如果带有 Last-Modified ，下一次发送 Http请求时，将会发生带 If-modified-since 的 HttpHeader 。如果没有过期，将会收到 304 的响应，从缓存中读取。

浏览器请求文件时,会先获取服务器的文件的最后修改时间，再和本地浏览器缓 存中的文件时间相比，如果没有发生变化就返回给浏览器304的状态码，表示没 有发生变化，然后浏览器就使用的本地的缓存展示资源,如果变化,则重新再一次 向服务器请求资源

此方式也需要向服务器发送请求才可以使用缓存

Etag 是 HttpHeader 中代表资源的标签，在服务器端生成。如果带有 Etag，下 一次发送带 Etag 的请求，如果 Etag 没有变化将收到 304的响应，从缓存中读 取。

基于Etag标记是否一致做判断页面是否发生过变化，比如基于Nginx 的etag on来实现。

Etag 在使用时要注意相同资源多台 Web 服务器的 Etag 的一致性

此方式也需要向服务器发送请求才可以使用缓存

以上两种都需要发送请求，即不管资源是否过期都要发送请求进行协商，这样会消耗不必要的时间，因此有了缓存的过期时间

Expire 是 HttpHeader 中代表资源的过期时间，由服务器端设置。如果带有 Expire ，则在 Expire 过期前不会发生 Http请求，直接从缓存中读取。用户强 制 F5 例外

第一次请求资源时,响应报文带有资源的过期时间，默认为30天，当前此方式使 用的比较多，但是无法保证客户的时间都是准确并且一致的，因此会加入一个最 大生存周期，使用用户本地的时间计算缓存数据是否超过多少天，下面的过期时 间Expires:为2028年，但是缓存的最大生存周期Cache-Control: max-age=315360000，计算为天等于3650天即10年

通常 Last-Modified,Etag,Expire 是一起混合使用的

• 特别是 Last-Modified 和 Expire 经常一起使用，因为 Expire可以让浏览器 完全不发起 Http 请求，而当浏览器强制 F5 的时候又有Last-Modified ，这 样就很好的达到了浏览器段缓存的效果。
• Etag 和 Expire 一起使用时，先判断 Expire ，如果已经过期，再发起 Http 请求，如果 Etag 变化了，则返回 200 响应。如果 Etag 没有变化,则返回 304响应。
• Last-Modified,Etag,Expires 三个同时使用时。先判断 Expire ，然后发送 Http 请求，服务器先判断 last-modified ，再判断 Etag，必须都没有过期， 才能返回 304 响应。

缓存刷新

• 第一次访问,获取最新数据,返回 200响应码
• 鼠标点击二次访问(Cache),输入地址后回车,浏览器对所有没有过期的内容直 接使用本地缓存。
• F5或点刷新按钮,会向服务器发送请求缓存协商信息,last-modified和etag会 有影响,但expires本地过期时间不受影响,无变化返回304
• 按Ctrl+F5强制刷新,所有缓存不再使用,直接连接服务器,获取最新数据,返回200响应码

#CentOS 8 由系统源提供
[root@centos8 ~]#yum info redis
Installed Packages
Name         : redis
Version      : 5.0.3
Release      : 1.module_el8.0.0+6+ab019c03
Arch         : x86_64
Size         : 3.3 M
Source       : redis-5.0.3-1.module_el8.0.0+6+ab019c03.src.rpm
Repo         : @System
From repo    : AppStream
Summary      : A persistent key-value database
URL          : http://redis.io
License      : BSD and MIT
Description  : Redis is an advanced key-value store. It is often referred to as a data
             : structure server since keys can contain strings, hashes, lists, sets and
             : sorted sets.
             : 
             : You can run atomic operations on these types, like appending to a string;
             : incrementing the value in a hash; pushing to a list; computing set
             : intersection, union and difference; or getting the member with highest
             : ranking in a sorted set.
             : 
             : In order to achieve its outstanding performance, Redis works with an
             : in-memory dataset. Depending on your use case, you can persist it either
             : by dumping the dataset to disk every once in a while, or by appending
             : each command to a log.
             : 
             : Redis also supports trivial-to-setup master-slave replication, with very
             : fast non-blocking first synchronization, auto-reconnection on net split
             : and so forth.
             : 
             : Other features include Transactions, Pub/Sub, Lua scripting, Keys with a
             : limited time-to-live, and configuration settings to make Redis behave like
             : a cache.
             : 
             : You can use Redis from most programming languages also.

#CentOS 7 由epel源提供
[root@node7 ~]# yum info redis
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.aliyun.com
 * epel: mirrors.aliyun.com
 * extras: mirrors.aliyun.com
Available Packages
Name        : redis
Arch        : x86_64
Version     : 3.2.12
Release     : 2.el7
Size        : 544 k
Repo        : epel/7/x86_64
Summary     : A persistent key-value database
URL         : http://redis.io
License     : BSD
Description : Redis is an advanced key-value store. It is often referred to as a data
            : structure server since keys can contain strings, hashes, lists, sets and
            : sorted sets.
            : 
            : You can run atomic operations on these types, like appending to a string;
            : incrementing the value in a hash; pushing to a list; computing set
            : intersection, union and difference; or getting the member with highest
            : ranking in a sorted set.
            : 
            : In order to achieve its outstanding performance, Redis works with an
            : in-memory dataset. Depending on your use case, you can persist it either
            : by dumping the dataset to disk every once in a while, or by appending
            : each command to a log.
            : 
            : Redis also supports trivial-to-setup master-slave replication, with very
            : fast non-blocking first synchronization, auto-reconnection on net split
            : and so forth.
            : 
            : Other features include Transactions, Pub/Sub, Lua scripting, Keys with a
            : limited time-to-live, and configuration settings to make Redis behave like
            : a cache.
            : 
            : You can use Redis from most programming languages also.

[root@centos8 ~]#dnf -y install redis
[root@centos8 ~]#systemctl enable --now redis

[root@centos8 ~]#ss -ntl
State       Recv-Q       Send-Q               Local Address:Port               Peer Address:Port       
LISTEN      0            128                        0.0.0.0:22                      0.0.0.0:*          
LISTEN      0            128                      127.0.0.1:6379                    0.0.0.0:*          
LISTEN      0            128                           [::]:22                         [::]:*

[root@centos8 ~]#pstree -p | grep redis
           |-redis-server(16812)-+-{redis-server}(16813)
           |                     |-{redis-server}(16814)
           |                     `-{redis-server}(16815)

[root@centos8 ~]#redis-cli 
127.0.0.1:6379> ping
PONG
127.0.0.1:6379> info
# Server
redis_version:5.0.3
redis_git_sha1:00000000
redis_git_dirty:0
redis_build_id:8c0bf22bfba82c8f
redis_mode:standalone
os:Linux 4.18.0-80.el8.x86_64 x86_64
arch_bits:64
multiplexing_api:epoll
atomicvar_api:atomic-builtin
gcc_version:8.2.1
process_id:16812
run_id:2af1a9195554cb7d268b5e782b58e3a23135c418
tcp_port:6379
uptime_in_seconds:89
uptime_in_days:0
hz:10
configured_hz:10
lru_clock:9451885
executable:/usr/bin/redis-server
config_file:/etc/redis.conf

# Clients
connected_clients:1
client_recent_max_input_buffer:2
client_recent_max_output_buffer:0
blocked_clients:0

# Memory
used_memory:853896
used_memory_human:833.88K
used_memory_rss:13012992
used_memory_rss_human:12.41M
used_memory_peak:853896
used_memory_peak_human:833.88K
used_memory_peak_perc:100.12%
used_memory_overhead:840694
used_memory_startup:791000
used_memory_dataset:13202
used_memory_dataset_perc:20.99%
allocator_allocated:1477016
allocator_active:1806336
allocator_resident:8712192
total_system_memory:836886528
total_system_memory_human:798.12M
used_memory_lua:37888
used_memory_lua_human:37.00K
used_memory_scripts:0
used_memory_scripts_human:0B
number_of_cached_scripts:0
maxmemory:0
maxmemory_human:0B
maxmemory_policy:noeviction
allocator_frag_ratio:1.22
allocator_frag_bytes:329320
allocator_rss_ratio:4.82
allocator_rss_bytes:6905856
rss_overhead_ratio:1.49
rss_overhead_bytes:4300800
mem_fragmentation_ratio:16.03
mem_fragmentation_bytes:12201096
mem_not_counted_for_evict:0
mem_replication_backlog:0
mem_clients_slaves:0
mem_clients_normal:49694
mem_aof_buffer:0
mem_allocator:jemalloc-5.1.0
active_defrag_running:0
lazyfree_pending_objects:0

# Persistence
loading:0
rdb_changes_since_last_save:0
rdb_bgsave_in_progress:0
rdb_last_save_time:1603287316
rdb_last_bgsave_status:ok
rdb_last_bgsave_time_sec:-1
rdb_current_bgsave_time_sec:-1
rdb_last_cow_size:0
aof_enabled:0
aof_rewrite_in_progress:0
aof_rewrite_scheduled:0
aof_last_rewrite_time_sec:-1
aof_current_rewrite_time_sec:-1
aof_last_bgrewrite_status:ok
aof_last_write_status:ok
aof_last_cow_size:0

# Stats
total_connections_received:1
total_commands_processed:2
instantaneous_ops_per_sec:0
total_net_input_bytes:45
total_net_output_bytes:11475
instantaneous_input_kbps:0.00
instantaneous_output_kbps:0.00
rejected_connections:0
sync_full:0
sync_partial_ok:0
sync_partial_err:0
expired_keys:0
expired_stale_perc:0.00
expired_time_cap_reached_count:0
evicted_keys:0
keyspace_hits:0
keyspace_misses:0
pubsub_channels:0
pubsub_patterns:0
latest_fork_usec:0
migrate_cached_sockets:0
slave_expires_tracked_keys:0
active_defrag_hits:0
active_defrag_misses:0
active_defrag_key_hits:0
active_defrag_key_misses:0

# Replication
role:master
connected_slaves:0
master_replid:cc6c17d57ae2848acfa6c93c116b3fb7e9bc305b
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:0
second_repl_offset:-1
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0

# CPU
used_cpu_sys:0.113862
used_cpu_user:0.015991
used_cpu_sys_children:0.000000
used_cpu_user_children:0.000000

# Cluster
cluster_enabled:0

# Keyspace
127.0.0.1:6379> 

官方的安装方法：

https://redis.io/download

范例：编译安装过程

#安装依赖包
[root@centos8 ~]#yum -y install make gcc tcl

#下载源码包
[root@centos8 ~]#wget http://download.redis.io/releases/redis-5.0.9.tar.gz
[root@centos8 ~]#tar xf redis-5.0.9.tar.gz

#编译安装
[root@centos8 ~]#cd redis-5.0.9/
[root@centos8 redis-5.0.9]#cd src/
[root@centos8 src]#make
[root@centos8 src]#make PREFIX=/apps/redis install

配置变量
[root@centos8 src]#echo "PATH=/apps/redis/bin:$PATH" > /etc/profile.d/redis.sh
[root@centos8 src]#. /etc/profile.d/redis.sh

#目录结构
[root@centos8 src]#tree /apps/redis/
/apps/redis/
└── bin
    ├── redis-benchmark
    ├── redis-check-aof
    ├── redis-check-rdb
    ├── redis-cli
    ├── redis-sentinel -> redis-server
    └── redis-server

1 directory, 6 files

#准备相关目录和文件
[root@centos8 ~]#mkdir /apps/redis/{etc,log,data,run}
[root@centos8 ~]#cp redis-5.0.9/redis.conf /apps/redis/etc/

redis-server 是redis 服务器程序

[root@centos8 ~]#redis-server --help
Usage: ./redis-server [/path/to/redis.conf] [options]
       ./redis-server - (read config from stdin)
       ./redis-server -v or --version
       ./redis-server -h or --help
       ./redis-server --test-memory <megabytes>

Examples:
       ./redis-server (run the server with default conf)
       ./redis-server /etc/redis/6379.conf
       ./redis-server --port 7777
       ./redis-server --port 7777 --replicaof 127.0.0.1 8888
       ./redis-server /etc/myredis.conf --loglevel verbose

Sentinel mode:
       ./redis-server /etc/sentinel.conf --sentinel

前台启动 redis

[root@centos8 ~]#redis-server /apps/redis/etc/redis.conf 
16418:C 22 Oct 2020 10:43:29.813 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
16418:C 22 Oct 2020 10:43:29.813 # Redis version=5.0.9, bits=64, commit=00000000, modified=0, pid=16418, just started
16418:C 22 Oct 2020 10:43:29.813 # Configuration loaded
16418:M 22 Oct 2020 10:43:29.814 * Increased maximum number of open files to 10032 (it was originally set to 1024).
                _._                                                  
           _.-``__ ''-._                                             
      _.-``    `.  `_.  ''-._           Redis 5.0.9 (00000000/0) 64 bit
  .-`` .-```.  ```\/    _.,_ ''-._                                   
 (    '      ,       .-`  | `,    )     Running in standalone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6379
 |    `-._   `._    /     _.-'    |     PID: 16418
  `-._    `-._  `-./  _.-'    _.-'                                   
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 |    `-._`-._        _.-'_.-'    |           http://redis.io        
  `-._    `-._`-.__.-'_.-'    _.-'                                   
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 |    `-._`-._        _.-'_.-'    |                                  
  `-._    `-._`-.__.-'_.-'    _.-'                                   
      `-._    `-.__.-'    _.-'                                       
          `-._        _.-'                                           
              `-.__.-'                                               

16418:M 22 Oct 2020 10:43:29.815 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
16418:M 22 Oct 2020 10:43:29.815 # Server initialized
16418:M 22 Oct 2020 10:43:29.815 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
16418:M 22 Oct 2020 10:43:29.815 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo madvise > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled (set to 'madvise' or 'never').
16418:M 22 Oct 2020 10:43:29.815 * Loading RDB produced by version 6.0.8
16418:M 22 Oct 2020 10:43:29.815 * RDB age 603 seconds
16418:M 22 Oct 2020 10:43:29.815 * RDB memory usage when created 0.77 Mb
16418:M 22 Oct 2020 10:43:29.815 * DB loaded from disk: 0.000 seconds
16418:M 22 Oct 2020 10:43:29.815 * Ready to accept connections

[root@centos8 ~]#ss -ntl
State       Recv-Q       Send-Q               Local Address:Port               Peer Address:Port       
LISTEN      0            128                        0.0.0.0:22                      0.0.0.0:*          
LISTEN      0            128                      127.0.0.1:6379                    0.0.0.0:*          
LISTEN      0            128                           [::]:22                         [::]:*

范例：开启多实例

#安装依赖包
[root@centos8 ~]#yum -y install make gcc tcl

#下载源码包
[root@centos8 ~]#wget http://download.redis.io/releases/redis-5.0.9.tar.gz
[root@centos8 ~]#tar xf redis-5.0.9.tar.gz

#编译安装
[root@centos8 ~]#cd redis-5.0.9/
[root@centos8 redis-5.0.9]#cd deps
[root@centos8 deps]#make hiredis lua jemalloc linenoise
[root@centos8 deps]#cd ../src
[root@centos8 src]#make
[root@centos8 src]#make PREFIX=/apps/redis/6379 install

配置变量
[root@centos8 src]#echo "PATH=/apps/redis/6379/bin:$PATH" > /etc/profile.d/redis.sh
[root@centos8 src]#. /etc/profile.d/redis.sh

#目录结构
[root@centos8 src]#tree /apps/redis/6379
/apps/redis/
└── bin
    ├── redis-benchmark
    ├── redis-check-aof
    ├── redis-check-rdb
    ├── redis-cli
    ├── redis-sentinel -> redis-server
    └── redis-server

1 directory, 6 files

#准备相关目录和文件
[root@centos8 ~]#mkdir /apps/redis/6379/{etc,log,data,run}
[root@centos8 ~]#cp redis-5.0.9/redis.conf /apps/redis/6379/etc/

#前台启动redis 6379
[root@centos8 redis]#redis-server --port 6379
17024:C 22 Oct 2020 11:09:08.749 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
17024:C 22 Oct 2020 11:09:08.749 # Redis version=5.0.9, bits=64, commit=00000000, modified=0, pid=17024, just started
17024:C 22 Oct 2020 11:09:08.749 # Configuration loaded
17024:M 22 Oct 2020 11:09:08.750 * Increased maximum number of open files to 10032 (it was originally set to 1024).
                _._                                                  
           _.-``__ ''-._                                             
      _.-``    `.  `_.  ''-._           Redis 5.0.9 (00000000/0) 64 bit
  .-`` .-```.  ```\/    _.,_ ''-._                                   
 (    '      ,       .-`  | `,    )     Running in standalone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6379
 |    `-._   `._    /     _.-'    |     PID: 17024
  `-._    `-._  `-./  _.-'    _.-'                                   
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 |    `-._`-._        _.-'_.-'    |           http://redis.io        
  `-._    `-._`-.__.-'_.-'    _.-'                                   
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 |    `-._`-._        _.-'_.-'    |                                  
  `-._    `-._`-.__.-'_.-'    _.-'                                   
      `-._    `-.__.-'    _.-'                                       
          `-._        _.-'                                           
              `-.__.-'                                               

17024:M 22 Oct 2020 11:09:08.751 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
17024:M 22 Oct 2020 11:09:08.751 # Server initialized
17024:M 22 Oct 2020 11:09:08.751 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
17024:M 22 Oct 2020 11:09:08.751 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo madvise > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled (set to 'madvise' or 'never').
17024:M 22 Oct 2020 11:09:08.751 * Ready to accept connections
[root@centos8 ~]#ss -ntl
State       Recv-Q       Send-Q               Local Address:Port               Peer Address:Port       
LISTEN      0            128                        0.0.0.0:22                      0.0.0.0:*          
LISTEN      0            128                        0.0.0.0:6379                    0.0.0.0:*          
LISTEN      0            128                           [::]:22                         [::]:*          
LISTEN      0            128                           [::]:6379                       [::]:* 
[root@centos8 ~]#redis-cli -p 6379
127.0.0.1:6379>

#为6380准备相关目录和文件
[root@centos8 ~]#mkdir /apps/redis/6380
[root@centos8 ~]#cp -ar /apps/redis/6379/* /apps/redis/6380/
[root@centos8 ~]#tree -d /apps/redis/
/apps/redis/
├── 6379
│   ├── bin
│   ├── data
│   ├── etc
│   ├── log
│   └── run
└── 6380
    ├── bin
    ├── data
    ├── etc
    ├── log
    └── run

12 directories

[root@centos8 ~]#vim /apps/redis/6380/etc/redis.conf 
port 6380

#前端启动6380
[root@centos8 ~]#redis-server --port 6380
17191:C 22 Oct 2020 11:17:28.354 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
17191:C 22 Oct 2020 11:17:28.354 # Redis version=5.0.9, bits=64, commit=00000000, modified=0, pid=17191, just started
17191:C 22 Oct 2020 11:17:28.354 # Configuration loaded
17191:M 22 Oct 2020 11:17:28.355 * Increased maximum number of open files to 10032 (it was originally set to 1024).
                _._                                                  
           _.-``__ ''-._                                             
      _.-``    `.  `_.  ''-._           Redis 5.0.9 (00000000/0) 64 bit
  .-`` .-```.  ```\/    _.,_ ''-._                                   
 (    '      ,       .-`  | `,    )     Running in standalone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6380
 |    `-._   `._    /     _.-'    |     PID: 17191
  `-._    `-._  `-./  _.-'    _.-'                                   
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 |    `-._`-._        _.-'_.-'    |           http://redis.io        
  `-._    `-._`-.__.-'_.-'    _.-'                                   
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 |    `-._`-._        _.-'_.-'    |                                  
  `-._    `-._`-.__.-'_.-'    _.-'                                   
      `-._    `-.__.-'    _.-'                                       
          `-._        _.-'                                           
              `-.__.-'                                               

17191:M 22 Oct 2020 11:17:28.355 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
17191:M 22 Oct 2020 11:17:28.355 # Server initialized
17191:M 22 Oct 2020 11:17:28.355 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
17191:M 22 Oct 2020 11:17:28.355 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo madvise > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled (set to 'madvise' or 'never').
17191:M 22 Oct 2020 11:17:28.355 * Loading RDB produced by version 6.0.8
17191:M 22 Oct 2020 11:17:28.355 * RDB age 1726 seconds
17191:M 22 Oct 2020 11:17:28.356 * RDB memory usage when created 0.77 Mb
17191:M 22 Oct 2020 11:17:28.356 * DB loaded from disk: 0.000 seconds
17191:M 22 Oct 2020 11:17:28.356 * Ready to accept connections
[root@centos8 ~]#ss -ntl
State       Recv-Q       Send-Q               Local Address:Port               Peer Address:Port       
LISTEN      0            128                        0.0.0.0:22                      0.0.0.0:*          
LISTEN      0            128                        0.0.0.0:6379                    0.0.0.0:*          
LISTEN      0            128                        0.0.0.0:6380                    0.0.0.0:*          
LISTEN      0            128                           [::]:22                         [::]:*          
LISTEN      0            128                           [::]:6379                       [::]:*          
LISTEN      0            128                           [::]:6380                       [::]:*

[root@centos8 ~]#redis-cli -p 6380
127.0.0.1:6380>

[root@centos8 ~]#useradd -r -s /sbin/nologin redis
#设置目录权限
[root@centos8 ~]#chown -R redis.redis /apps/redis/

redis 支持多种开发语言访问

https://redis.io/clients

#设置连接密码
127.0.0.1:6379> CONFIG SET requirepass centos
OK

#查看连接密码
127.0.0.1:6379> CONFIG GET requirepass
1) "requirepass"
2) "centos"

#奇数行为键，偶数行为值
127.0.0.1:6379> CONFIG GET *
  1) "dbfilename"
  2) "dump_6379.rdb"
  3) "requirepass"
  4) "centos"
  5) "masterauth"
  6) ""
  7) "cluster-announce-ip"
  8) ""
  9) "unixsocket"
 10) ""
...省略...

#查看bind
127.0.0.1:6379> CONFIG GET bind
1) "bind"
2) "0.0.0.0"

#有些设置无法修改
127.0.0.1:6379> CONFIG SET bind 127.0.0.1
(error) ERR Unsupported CONFIG parameter: bind

127.0.0.1:6379> CONFIG SET maxmemory 8589934592
OK
127.0.0.1:6379> CONFIG GET maxmemory
1) "maxmemory"
2) "8589934592"

如果主要充当缓存功能,或者可以承受数分钟数据的丢失, 通常生产环境一般只需启用RDB即可,此也是默认值

如果数据需要持久保存,一点不能丢失,可以选择同时开启RDB和AOF,一般不建议只开启AOF

set 指令可以创建一个key 并赋值, 使用格式：

SET key value [EX seconds] [PX milliseconds] [NX|XX]
时间复杂度： O(1)
将字符串值 value 关联到 key 。

如果 key 已经持有其他值， SET 就覆写旧值， 无视类型。
当 SET 命令对一个带有生存时间（TTL）的键进行设置之后， 该键原有的 TTL 将被清除。

从 Redis 2.6.12 版本开始， SET 命令的行为可以通过一系列参数来修改：
EX seconds ： 将键的过期时间设置为 seconds 秒。 执行 SET key value EX seconds 的效果等同于执行 SETEX key seconds value 。
PX milliseconds ： 将键的过期时间设置为 milliseconds 毫秒。 执行 SET key value PX milliseconds 的效果等同于执行 PSETEX key milliseconds value 。
NX ： 只在键不存在时， 才对键进行设置操作。 执行 SET key value NX 的效果等同于执行 SETNX key value 。
XX ： 只在键已经存在时， 才对键进行设置操作。

范例：

127.0.0.1:6379> set key1 value1
OK
127.0.0.1:6379> get key1
"value1"
127.0.0.1:6379> type key1
string
127.0.0.1:6379> set title ceo ex 5  #设置自动过期时间为5秒
OK
127.0.0.1:6379> get title
"ceo"
127.0.0.1:6379> get title
(nil)
#大小写敏感
127.0.0.1:6379> set NAME KOBE
OK
127.0.0.1:6379> get NAME
"KOBE"
127.0.0.1:6379> get name
(nil)
127.0.0.1:6379> set name brynat
OK
127.0.0.1:6379> get name
"brynat"
127.0.0.1:6379> get NAME
"KOBE"

#key不存在才设置，相当于add
127.0.0.1:6379> get name
"brynat"
127.0.0.1:6379> set name tao nx
(nil)

#key存在才设置，相当于update
127.0.0.1:6379> get name
"brynat"
127.0.0.1:6379> set name tao xx
OK
127.0.0.1:6379> get name
"tao"
127.0.0.1:6379> get age
(nil)
127.0.0.1:6379> set age 23 xx
(nil)
127.0.0.1:6379> get age
(nil)

127.0.0.1:6379> get NAME
"KOBE"
127.0.0.1:6379> get name age
(error) ERR wrong number of arguments for 'get' command

LPUSH和RPUSH都可以插入列表

LPUSH key value [value …]
时间复杂度： O(1)
将一个或多个值 value 插入到列表 key 的表头

如果有多个 value 值，那么各个 value 值按从左到右的顺序依次插入到表头： 比如说，对空列表mylist 执行命令 LPUSH mylist a b c ，列表的值将是 c b a ，这等同于原子性地执行 LPUSH
mylist a 、 LPUSH mylist b 和 LPUSH mylist c 三个命令。

如果 key 不存在，一个空列表会被创建并执行 LPUSH 操作。
当 key 存在但不是列表类型时，返回一个错误。

RPUSH key value [value …]
时间复杂度： O(1)
将一个或多个值 value 插入到列表 key 的表尾(最右边)。

如果有多个 value 值，那么各个 value 值按从左到右的顺序依次插入到表尾：比如对一个空列表mylist 执行 RPUSH mylist a b c ，得出的结果列表为 a b c ，等同于执行命令 RPUSH mylist
a 、 RPUSH mylist b 、 RPUSH mylist c 。

如果 key 不存在，一个空列表会被创建并执行 RPUSH 操作。
当 key 存在但不是列表类型时，返回一个错误。

范例:

#从左边添加数据，已添加的需向右移
127.0.0.1:6379> LPUSH name kobe bryant rose #根据顺序逐个写入name，最后的rose会在列表的最右侧
(integer) 3
127.0.0.1:6379> TYPE name
list

#从右边添加数据
127.0.0.1:6379> RPUSH course linux python go
(integer) 3
127.0.0.1:6379> TYPE course
list

127.0.0.1:6379> LPUSH name bob
(integer) 4
#从右边添加数据，已添加的向左移
127.0.0.1:6379> RPUSH name tom
(integer) 5

127.0.0.1:6379> LLEN name
(integer) 5
127.0.0.1:6379> LLEN course
(integer) 3

127.0.0.1:6379> LPUSH list1 a b c d
(integer) 4
127.0.0.1:6379> LINDEX list1 0 #获取0编号的元素
"d"
127.0.0.1:6379> LINDEX list1 3 #获取3编号的元素
"a"
127.0.0.1:6379> LINDEX list1 -1 #获取最后一个的元素
"a"

#元素从0开始编号
127.0.0.1:6379> LPUSH list1 a b c d
(integer) 4
127.0.0.1:6379> LRANGE list1 1 2
1) "c"
2) "b"
127.0.0.1:6379> LRANGE list1 0 3 #所有元素
1) "d"
2) "c"
3) "b"
4) "a"
127.0.0.1:6379> LRANGE list1 0 -1 #所有元素
1) "d"
2) "c"
3) "b"
4) "a"

127.0.0.1:6379> RPUSH list2 zhang wang li zhao
(integer) 4
127.0.0.1:6379> LRANGE list2 1 2 #指定范围
1) "wang"
2) "li"
127.0.0.1:6379> LRANGE list2 2 2 #指定位置
1) "li"
127.0.0.1:6379> LRANGE list2 0 -1 #所有元素
1) "zhang"
2) "wang"
3) "li"
4) "zhao"

127.0.0.1:6379> RPUSH listkey a b c d e f
(integer) 6
127.0.0.1:6379> lrange listkey 0 -1
1) "a"
2) "b"
3) "c"
4) "d"
5) "e"
6) "f"
127.0.0.1:6379> lset listkey 2 java
OK
127.0.0.1:6379> lrange listkey 0 -1
1) "a"
2) "b"
3) "java"
4) "d"
5) "e"
6) "f"
127.0.0.1:6379>

127.0.0.1:6379> LPUSH list1 a b c d
(integer) 4
127.0.0.1:6379> LRANGE list1 0 3
1) "d"
2) "c"
3) "b"
4) "a"
127.0.0.1:6379> LPOP list1 #弹出左边第一个元素，即删除第一个
"d"
127.0.0.1:6379> LLEN list1
(integer) 3
127.0.0.1:6379> LRANGE list1 0 2
1) "c"
2) "b"
3) "a"
127.0.0.1:6379> RPOP list1 #弹出右边第一个元素，即删除最后一个
"a"
127.0.0.1:6379> LLEN list1
(integer) 2
127.0.0.1:6379> LRANGE list1 0 1
1) "c"
2) "b"

#LTRIM 对一个列表进行修剪(trim)，让列表只保留指定区间内的元素，不在指定区间之内的元素都将被删
除
127.0.0.1:6379> LLEN list1
(integer) 4
127.0.0.1:6379> LRANGE list1 0 3
1) "d"
2) "c"
3) "b"
4) "a"
127.0.0.1:6379> LTRIM list1 1 2 #只保留1，2号元素
OK
127.0.0.1:6379> LLEN list1
(integer) 2
127.0.0.1:6379> LRANGE list1 0 1
1) "c"
2) "b"

#删除list
127.0.0.1:6379> DEL list1
(integer) 1
127.0.0.1:6379> EXISTS list1
(integer) 0

127.0.0.1:6379> SADD set1 v1
(integer) 1
127.0.0.1:6379> SADD set2 v2 v3
(integer) 2
127.0.0.1:6379> TYPE set1
set
127.0.0.1:6379> TYPE set2
set

#追加时，只能追加不存在的数据，不能追加已经存在的数据
127.0.0.1:6379> SADD set1 v1    #已存在的值，无法再次添加
(integer) 0
127.0.0.1:6379> SADD set1 v3 v4 v5
(integer) 3

127.0.0.1:6379> SMEMBERS set1
1) "v4"
2) "v3"
3) "v1"
4) "v2"
5) "v5"
127.0.0.1:6379> SMEMBERS set2
1) "v3"
2) "v2"

127.0.0.1:6379> SADD goods mobile car laptop
(integer) 3
127.0.0.1:6379> SREM goods car
(integer) 1
127.0.0.1:6379> SMEMBERS goods
1) "laptop"
2) "mobile"

集合见操作

交集：已属于A且属于B的元素称为A与B的交集

127.0.0.1:6379> SMEMBERS set1
1) "v4"
2) "v2"
3) "v5"
4) "v3"
127.0.0.1:6379> SMEMBERS set2
1) "v6"
2) "v3"
3) "v2"
127.0.0.1:6379> SINTER set1 set2
1) "v3"
2) "v2"

并集：已属于A或属于B的元素称为A与B的并集

127.0.0.1:6379> SMEMBERS set1
1) "v4"
2) "v2"
3) "v5"
4) "v3"
127.0.0.1:6379> SMEMBERS set2
1) "v6"
2) "v3"
3) "v2"
127.0.0.1:6379> SUNION set1 set2
1) "v5"
2) "v4"
3) "v2"
4) "v3"
5) "v6"

差集：已属于A而不属于B的元素称为A与B的差（集）

127.0.0.1:6379> SMEMBERS set1
1) "v4"
2) "v2"
3) "v5"
4) "v3"
127.0.0.1:6379> SMEMBERS set2
1) "v6"
2) "v3"
3) "v2"
127.0.0.1:6379> SDIFF set1 set2
1) "v4"
2) "v5"

127.0.0.1:6379> ZADD zset1 1 v1 #分数为1
(integer) 1
127.0.0.1:6379> ZADD zset1 2 v2
(integer) 1
127.0.0.1:6379> ZADD zset1 2 v3 #分数可重复，元素值不可以重复
(integer) 1
127.0.0.1:6379> ZADD zset1 3 v4
(integer) 1
127.0.0.1:6379> TYPE zset1
zset
127.0.0.1:6379> TYPE zset2
zset

#一次生成多个数据：
127.0.0.1:6379> ZADD zset2 1 v1 2 v2 3 v3 4 v4 5 v5
(integer) 5

127.0.0.1:6379> ZADD paihangbang 90 nezha 99 zhanlang 60 zhuluoji 30 gangtiexia
(integer) 4
127.0.0.1:6379> ZRANGE panghangbang 0 -1
(empty list or set)
127.0.0.1:6379> ZRANGE paihangbang 0 -1 #正序排序后显示集合内所有的key，score从小到大显示
1) "gangtiexia"
2) "zhuluoji"
3) "nezha"
4) "zhanlang"
127.0.0.1:6379> ZREVRANGE paihangbang 0 -1  #倒叙排序后显示集合内所有的key，score从大到小显示
1) "zhanlang"
2) "nezha"
3) "zhuluoji"
4) "gangtiexia"
127.0.0.1:6379> ZRANGE paihangbang 0 -1 withscores  #正序显示指定集合内所有key和得分情况
1) "gangtiexia"
2) "30"
3) "zhuluoji"
4) "60"
5) "nezha"
6) "90"
7) "zhanlang"
8) "99"
127.0.0.1:6379> ZREVRANGE paihangbang 0 -1 withscores   #倒叙显示指定集合内所有key和得分情况
1) "zhanlang"
2) "99"
3) "nezha"
4) "90"
5) "zhuluoji"
6) "60"
7) "gangtiexia"
8) "30"

127.0.0.1:6379> ZCARD paihangbang
(integer) 4
127.0.0.1:6379> ZCARD zset
(integer) 4

127.0.0.1:6379> ZRANGE paihangbang 0 2
1) "gangtiexia"
2) "zhuluoji"
3) "nezha"
127.0.0.1:6379> ZRANGE paihangbang 0 10 #超出范围不报错
1) "gangtiexia"
2) "zhuluoji"
3) "nezha"
4) "zhanlang"
127.0.0.1:6379> ZRANGE zset 1 3
1) "v2"
2) "v3"
3) "v4"
127.0.0.1:6379> ZRANGE zset 0 2
1) "v1"
2) "v2"
3) "v3"
127.0.0.1:6379> ZRANGE zset 2 2
1) "v3"

127.0.0.1:6379> ZADD paihangbang 90 nezha 99 zhanlang 60 zhuluoji 30 gangtiexia
(integer) 4
127.0.0.1:6379> ZRANGE paihangbang 0 -1
1) "gangtiexia"
2) "zhuluoji"
3) "nezha"
4) "zhanlang"
127.0.0.1:6379> ZRANK paihangbang zhanlang
(integer) 3 #取第4个
127.0.0.1:6379> ZRANK paihangbang zhuluoji
(integer) 1 #取第2个

127.0.0.1:6379> ZSCORE paihangbang zhuluoji
"60"
127.0.0.1:6379> ZSCORE paihangbang nezha
"90"

127.0.0.1:6379> ZADD paihangbang 90 nezha 199 zhanlang 60 zhuluoji 30 gangtiexia
(integer) 4
127.0.0.1:6379> ZRANGE paihangbang 0 -1
1) "gangtiexia"
2) "zhuluoji"
3) "nezha"
4) "zhanlang"
127.0.0.1:6379> ZREM paihangbang zhuluoji nezha
(integer) 2
127.0.0.1:6379> ZRANGE paihangbang 0 -1
1) "gangtiexia"
2) "zhanlang"

格式：

HSET hash field value
时间复杂度： O(1)
将哈希表 hash 中域 field 的值设置为 value 。

如果给定的哈希表并不存在， 那么一个新的哈希表将被创建并执行 HSET 操作。
如果域 field 已经存在于哈希表中， 那么它的旧值将被新值 value 覆盖。

范例:

127.0.0.1:6379> HSET 9527 name zhouxingxing age 20
(integer) 2
127.0.0.1:6379> type 9527
hash

#查看所有字段的值
127.0.0.1:6379> HGETALL 9527
1) "name"
2) "zhouxingxing"
3) "age"
4) "20"

#增加字段
127.0.0.1:6379> HSET 9527 gender male
(integer) 1
127.0.0.1:6379> HGETALL 9527
1) "name"
2) "zhouxingxing"
3) "age"
4) "20"
5) "gender"
6) "male"

127.0.0.1:6379> HGET 9527 name
"zhouxingxing"
127.0.0.1:6379> HGET 9527 age
"20"

127.0.0.1:6379> HMGET 9527 age gender   #获取多个值
1) "20"
2) "male"

127.0.0.1:6379> HDEL 9527 age
(integer) 1
127.0.0.1:6379> HGET 9527 age
(nil)

127.0.0.1:6379> HGETALL 9527
1) "name"
2) "zhouxingxing"
3) "gender"
4) "male"

127.0.0.1:6379> HGET 9527 name
"zhouxingxing"

127.0.0.1:6379> HMSET 1024 name chenglong age 60 city hongkong
OK
127.0.0.1:6379> HGETALL 1024
1) "name"
2) "chenglong"
3) "age"
4) "60"
5) "city"
6) "hongkong"

127.0.0.1:6379> HMSET 1024 name chenglong age 60 city hongkong
OK
127.0.0.1:6379> HMGET 1024 name city
1) "chenglong"
2) "hongkong"

127.0.0.1:6379> HMSET 1024 name chenglong age 60 city hongkong
OK
127.0.0.1:6379> HKEYS 1024
1) "name"
2) "age"
3) "city"

127.0.0.1:6379> HMSET 1024 name chenglong age 60 city hongkong
OK
127.0.0.1:6379> HVALS 1024
1) "chenglong"
2) "60"
3) "hongkong"

127.0.0.1:6379> HGETALL 1024
1) "name"
2) "chenglong"
3) "age"
4) "60"
5) "city"
6) "hongkong"

127.0.0.1:6379> DEL 1024
(integer) 1
127.0.0.1:6379> HMGET 1024 name age
1) (nil)
2) (nil)
127.0.0.1:6379> EXISTS 1024
(integer) 0

生产者消费者模式下，多个消费者同时监听一个队列，但是一个消息只能被最先 抢到消息的消费者消费，即消息任务是一次性读取和处理，此模式在分布式业务 架构中很常用，比较常用的消息队列软件还有RabbitMQ、Kafka、RocketMQ、 ActiveMQ等。

队列当中的消息由不同的生产者写入，也会有不同的消费者取出进行消费处理，但是一个消息一定是只能被取出一次也就是被消费一次。

[root@redis ~]# redis-cli
127.0.0.1:6379> AUTH 123456
OK
127.0.0.1:6379> LPUSH channel1 msg1 #从管道的左侧写入
(integer) 1
127.0.0.1:6379> LPUSH channel1 msg2
(integer) 2
127.0.0.1:6379> LPUSH channel1 msg3
(integer) 3
127.0.0.1:6379> LPUSH channel1 msg4
(integer) 4
127.0.0.1:6379> LPUSH channel1 msg5
(integer) 5

127.0.0.1:6379> LRANGE channel1 0 -1
1) "msg5"
2) "msg4"
3) "msg3"
4) "msg2"
5) "msg1"

127.0.0.1:6379> RPOP channel1 #从管道的右侧消费，用于消息的先进先出
"msg1"
127.0.0.1:6379> RPOP channel1
"msg2"
127.0.0.1:6379> RPOP channel1
"msg3"
127.0.0.1:6379> RPOP channel1
"msg4"
127.0.0.1:6379> RPOP channel1
"msg5"
127.0.0.1:6379> RPOP channel1
(nil)

127.0.0.1:6379> LRANGE channel1 0 -1
(empty list or set)     #队列中的消息已经被已全部消费完毕

在发布者订阅者模式下，发布者将消息发布到指定的channel里面，凡是监听该 channel的消费者都会收到同样的一份消息，这种模式类似于是收音机的广播模 式，即凡是收听某个频道的听众都会收到主持人发布的相同的消息内容。此模式 常用于群聊天、群通知、群公告等场景

• Publisher：发布者
• Subscriber：订阅者
• Channel：频道

[root@redis ~]# redis-cli
127.0.0.1:6379> AUTH 123456
OK
127.0.0.1:6379> SUBSCRIBE channel1      #订阅者事先订阅指定的频道，之后发布的消息才能收到
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "channel1"
3) (integer) 1

127.0.0.1:6379> PUBLISH channel1 test1 #发布者发布消息
(integer) 2     #订阅者个数
127.0.0.1:6379> PUBLISH channel1 test2
(integer) 2

#订阅指定的多个频道
127.0.0.1:6379> SUBSCRIBE channel1 channel2

127.0.0.1:6379> PSUBSCRIBE *    #支持通配符*

127.0.0.1:6379> PSUBSCRIBE chann*   #匹配订阅多个频道

127.0.0.1:6379> unsubscribe channel1
1) "unsubscribe"
2) "channel1"
3) (integer) 0

范例:

1)在slave1上
[root@slave1 ~]#grep replicaof /etc/redis.conf 
# Master-Replica replication. Use replicaof to make a Redis instance a copy of
# replicaof <masterip> <masterport>
[root@slave1 ~]#sed -ri "s/^# (replicaof).*/\1 10.0.0.8 6379/" /etc/redis.conf 
[root@slave1 ~]#grep replicaof /etc/redis.conf 
# Master-Replica replication. Use replicaof to make a Redis instance a copy of
replicaof 10.0.0.8 6379 #指定master的IP和端口号
[root@slave1 ~]#grep masterauth /etc/redis.conf 
# masterauth <master-password>
[root@slave1 ~]#sed -ri "s/^# (masterauth).*/\1 centos/" /etc/redis.conf 
[root@slave1 ~]#grep masterauth /etc/redis.conf 
masterauth centos   #设置密码
[root@slave1 ~]#systemctl restart redis

2)在slave2上
[root@slave2 ~]#grep replicaof /etc/redis.conf
# Master-Replica replication. Use replicaof to make a Redis instance a copy of
# replicaof <masterip> <masterport>
[root@slave2 ~]#sed -ri "s/^# (replicaof).*/\1 10.0.0.8 6379/" /etc/redis.conf
[root@slave2 ~]#grep replicaof /etc/redis.conf
# Master-Replica replication. Use replicaof to make a Redis instance a copy of
replicaof 10.0.0.8 6379
[root@slave2 ~]#grep masterauth /etc/redis.conf
# masterauth <master-password>
[root@slave2 ~]#sed -ri "s/^# (masterauth).*/\1 centos/" /etc/redis.conf
[root@slave2 ~]#grep masterauth /etc/redis.conf
masterauth centos
[root@slave2 ~]#systemctl restart redis

#在master上查看状态
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:2
slave0:ip=10.0.0.18,port=6379,state=online,offset=2520,lag=1
slave1:ip=10.0.0.28,port=6379,state=online,offset=2520,lag=0
master_replid:f68659a5c6e8381dbbdd6841f5b89d1a60157af8
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:2520
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:2520

#在slave上查看状态和数据
1)在slave1上
127.0.0.1:6379> get key1    #同步成功后，slave上的key信息丢失，从master复制过来新的值
"v1-master"
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:10.0.0.8
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:2660
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:f68659a5c6e8381dbbdd6841f5b89d1a60157af8
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:2660
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2283
repl_backlog_histlen:378
2)在slave2上
127.0.0.1:6379> get key1
"v1-master"
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:10.0.0.8
master_port:6379
master_link_status:up
master_last_io_seconds_ago:10
master_sync_in_progress:0
slave_repl_offset:2786
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:f68659a5c6e8381dbbdd6841f5b89d1a60157af8
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:2786
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2493
repl_backlog_histlen:294

#停止master的redis服务：systemctl stop redis，在slave上可以看到以下现象
[root@master ~]#systemctl stop redis
#在slave1上，同样在islave2上也是
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:10.0.0.8
master_port:6379
master_link_status:down #显示down，表示无法连接master
master_last_io_seconds_ago:-1
master_sync_in_progress:0
slave_repl_offset:2926
master_link_down_since_seconds:28
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:f68659a5c6e8381dbbdd6841f5b89d1a60157af8
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:2926
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2283
repl_backlog_histlen:644

#以slave1为例
7530:S 24 Oct 2020 12:46:47.815 * Connecting to MASTER 10.0.0.8:6379
7530:S 24 Oct 2020 12:46:47.816 * MASTER <-> REPLICA sync started
7530:S 24 Oct 2020 12:46:47.816 * Non blocking connect for SYNC fired the event.
7530:S 24 Oct 2020 12:46:47.831 * Master replied to PING, replication can continue...
7530:S 24 Oct 2020 12:46:47.832 * Trying a partial resynchronization (request 9507932f3addde3a76b51c5d6ecbb5daac398caa:1065).
7530:S 24 Oct 2020 12:46:47.848 * Full resync from master: f68659a5c6e8381dbbdd6841f5b89d1a60157af8:2282
7530:S 24 Oct 2020 12:46:47.848 * Discarding previously cached master state.
7530:S 24 Oct 2020 12:46:47.897 * MASTER <-> REPLICA sync: receiving 197 bytes from master
7530:S 24 Oct 2020 12:46:47.898 * MASTER <-> REPLICA sync: Flushing old data
7530:S 24 Oct 2020 12:46:47.898 * MASTER <-> REPLICA sync: Loading DB in memory
7530:S 24 Oct 2020 12:46:47.898 * MASTER <-> REPLICA sync: Finished with success
7530:S 24 Oct 2020 12:54:37.563 # Connection with master lost.
7530:S 24 Oct 2020 12:54:37.563 * Caching the disconnected master state.
7530:S 24 Oct 2020 12:54:38.117 * Connecting to MASTER 10.0.0.8:6379
7530:S 24 Oct 2020 12:54:38.118 * MASTER <-> REPLICA sync started
7530:S 24 Oct 2020 12:54:38.118 # Error condition on socket for SYNC: Connection refused

[root@master ~]#tail -f /var/log/redis/redis.log
2259:M 24 Oct 2020 11:48:48.987 * DB loaded from disk: 0.000 seconds
2259:M 24 Oct 2020 11:48:48.987 * Ready to accept connections
2259:M 24 Oct 2020 12:19:25.718 * Replica 10.0.0.18:6379 asks for synchronization
2259:M 24 Oct 2020 12:19:25.719 * Full resync requested by replica 10.0.0.18:6379
2259:M 24 Oct 2020 12:19:25.719 * Starting BGSAVE for SYNC with target: disk
2259:M 24 Oct 2020 12:19:25.719 * Background saving started by pid 2366
2366:C 24 Oct 2020 12:19:25.721 * DB saved on disk
2366:C 24 Oct 2020 12:19:25.721 * RDB: 0 MB of memory used by copy-on-write
2259:M 24 Oct 2020 12:19:25.772 * Background saving terminated with success
2259:M 24 Oct 2020 12:19:25.773 * Synchronization with replica 10.0.0.18:6379 succeeded
2259:M 24 Oct 2020 12:25:57.637 * Replica 10.0.0.28:6379 asks for synchronization
2259:M 24 Oct 2020 12:25:57.637 * Full resync requested by replica 10.0.0.28:6379
2259:M 24 Oct 2020 12:25:57.637 * Starting BGSAVE for SYNC with target: disk
2259:M 24 Oct 2020 12:25:57.638 * Background saving started by pid 2379
2379:C 24 Oct 2020 12:25:57.639 * DB saved on disk
2379:C 24 Oct 2020 12:25:57.639 * RDB: 0 MB of memory used by copy-on-write
2259:M 24 Oct 2020 12:25:57.717 * Background saving terminated with success
2259:M 24 Oct 2020 12:25:57.718 * Synchronization with replica 10.0.0.28:6379 succeeded
2259:M 24 Oct 2020 12:32:10.884 # Connection with replica 10.0.0.18:6379 lost.
2259:M 24 Oct 2020 12:46:47.832 * Replica 10.0.0.18:6379 asks for synchronization
2259:M 24 Oct 2020 12:46:47.833 * Partial resynchronization not accepted: Replication ID mismatch (Replica asked for '9507932f3addde3a76b51c5d6ecbb5daac398caa', my replication IDs are 'f68659a5c6e8381dbbdd6841f5b89d1a60157af8' and '0000000000000000000000000000000000000000')
2259:M 24 Oct 2020 12:46:47.833 * Starting BGSAVE for SYNC with target: disk
2259:M 24 Oct 2020 12:46:47.847 * Background saving started by pid 2466
2466:C 24 Oct 2020 12:46:47.850 * DB saved on disk
2466:C 24 Oct 2020 12:46:47.850 * RDB: 0 MB of memory used by copy-on-write
2259:M 24 Oct 2020 12:46:47.897 * Background saving terminated with success
2259:M 24 Oct 2020 12:46:47.897 * Synchronization with replica 10.0.0.18:6379 succeeded
2259:M 24 Oct 2020 12:49:17.963 # Connection with replica 10.0.0.28:6379 lost.
2259:M 24 Oct 2020 12:49:17.997 * Replica 10.0.0.28:6379 asks for synchronization
2259:M 24 Oct 2020 12:49:17.997 * Partial resynchronization request from 10.0.0.28:6379 accepted. Sending 0 bytes of backlog starting from offset 2493.
2259:M 24 Oct 2020 12:54:37.562 # User requested shutdown...
2259:M 24 Oct 2020 12:54:37.562 * Saving the final RDB snapshot before exiting.
2259:M 24 Oct 2020 12:54:37.563 * DB saved on disk
2259:M 24 Oct 2020 12:54:37.563 * Removing the pid file.
2259:M 24 Oct 2020 12:54:37.563 # Redis is now ready to exit, bye bye...

#这里以slave1为例
127.0.0.1:6379> set key1 v1-slave1-18
(error) READONLY You can't write against a read only replica.

假设当前主节点10.0.0.8故障，提升10.0.0.18为新的master

[root@master ~]#systemctl stop redis

#查看当前10.0.0.18节点的状态为slave，master指向10.0.0.8
[root@slave1 ~]#redis-cli -a centos
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:10.0.0.8
master_port:6379
master_link_status:down #master已宕掉
master_last_io_seconds_ago:-1
master_sync_in_progress:0
slave_repl_offset:2590
master_link_down_since_seconds:75
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:bdef83063c2c60b20a3ebc4d3794f0d8f95a4e44
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:2590
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:2590

停止slave1(10.0.0.18)同步并提升为新的master

#提升为新的master
127.0.0.1:6379> replicaof no one    #旧版使用SLAVEOF no one
OK
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:0
master_replid:37b3bdf32bb1ce3442a4b2d05dcb3a1ada2af352
master_replid2:bdef83063c2c60b20a3ebc4d3794f0d8f95a4e44
master_repl_offset:2590
second_repl_offset:2591
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:2590

#测试能否写入数据：
127.0.0.1:6379> set keytest1 vtest1
OK

修改所有的slave指向新的master节点

#修改10.0.0.28节点指向新的master节点10.0.0.18
127.0.0.1:6379> replicaof 10.0.0.18 6379
OK
127.0.0.1:6379> config set masterauth centos
OK
127.0.0.1:6379> set key100 v100
(error) READONLY You can't write against a read only replica.
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:10.0.0.18
master_port:6379
master_link_status:up
master_last_io_seconds_ago:10
master_sync_in_progress:0
slave_repl_offset:2736
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:37b3bdf32bb1ce3442a4b2d05dcb3a1ada2af352
master_replid2:bdef83063c2c60b20a3ebc4d3794f0d8f95a4e44
master_repl_offset:2736
second_repl_offset:2591
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:2736

#查看日志
7511:S 24 Oct 2020 14:25:12.275 * REPLICAOF 10.0.0.18:6379 enabled (user request from 'id=6 addr=127.0.0.1:51148 fd=7 name= age=277 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=44 qbuf-free=32724 obl=0 oll=0 omem=0 events=r cmd=replicaof')
7511:S 24 Oct 2020 14:25:12.492 * Connecting to MASTER 10.0.0.18:6379
7511:S 24 Oct 2020 14:25:12.492 * MASTER <-> REPLICA sync started
7511:S 24 Oct 2020 14:25:12.493 * Non blocking connect for SYNC fired the event.
7511:S 24 Oct 2020 14:25:12.494 * Master replied to PING, replication can continue...
7511:S 24 Oct 2020 14:25:12.497 * Trying a partial resynchronization (request 96542a696e2a90ac4197412fd2cc5a5c87d5d522:2891).
7511:S 24 Oct 2020 14:25:12.498 * Full resync from master: 37b3bdf32bb1ce3442a4b2d05dcb3a1ada2af352:2890
7511:S 24 Oct 2020 14:25:12.498 * Discarding previously cached master state.
7511:S 24 Oct 2020 14:25:12.539 * MASTER <-> REPLICA sync: receiving 214 bytes from master
7511:S 24 Oct 2020 14:25:12.539 * MASTER <-> REPLICA sync: Flushing old data
7511:S 24 Oct 2020 14:25:12.539 * MASTER <-> REPLICA sync: Loading DB in memory
7511:S 24 Oct 2020 14:25:12.539 * MASTER <-> REPLICA sync: Finished with success

在新master10.0.0.18上可看到slave

127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=10.0.0.28,port=6379,state=online,offset=3002,lag=0
master_replid:37b3bdf32bb1ce3442a4b2d05dcb3a1ada2af352
master_replid2:bdef83063c2c60b20a3ebc4d3794f0d8f95a4e44
master_repl_offset:3002
second_repl_offset:2591
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:3002

Redis主从复制分为全量同步和增量同步

Redis在2.8版本之前没有提供增量部分复制的功能，当网络闪断或者slave Redis重启之后会导致主从之间的全量同步，即从2.8版本开始增加了部分复制的功能。

性能相关配置

repl-diskless-sync no # 是否使用无盘同步RDB文件，默认为no，no为不使用无盘，需要将RDB文件保存到磁盘后再发送给slave，yes为支持无盘，支持无盘就是RDB文件不需要保存至本地磁盘，而且直接通过socket文件发送给slave

repl-diskless-sync-delay 5 #diskless时复制的服务器等待的延迟时间

repl-ping-slave-period 10 #slave端向server端发送ping的时间间隔，默认为10秒

repl-timeout 60 #设置主从ping连接超时时间,超过此值无法连接,master_link_status显示为down,并记录错误日志

repl-disable-tcp-nodelay no #是否启用TCP_NODELAY，如设置成yes，则redis会合并小的TCP包从而节省带宽， 但会增加同步延迟（40ms），造成master与slave数据不一致，假如设置成no，则redismaster会立即发送同步数据，没有延迟，yes关注性能，no关注redis服务中的数据一致性

repl-backlog-size 1mb #master的写入数据缓冲区，用于记录自上一次同步后到下一次同步过程中间的写入命令，计算公式：repl-backlog-size = 允许从节点最大中断时长 * 主实例offset每秒写入量，比如master每秒最大写入64mb，最大允许60秒，那么就要设置为64mb*60秒=3840MB(3.8G),建议此值是设置的足够大

repl-backlog-ttl 3600 #如果一段时间后没有slave连接到master，则backlog size的内存将会被释放。如果值为0则表示永远不释放这部份内存。

slave-priority 100 #slave端的优先级设置，值是一个整数，数字越小表示优先级越高。当master故障时将会按照优先级来选择slave端进行恢复，如果值设置为0，则表示该slave永远不会被选择。

min-replicas-to-write 1 #设置一个master的可用slave不能少于多少个，否则master无法执行写

min-slaves-max-lag 20 #设置至少有上面数量的slave延迟时间都大于多少秒时，master不接收写操作(拒绝写入)

即配置的master密码不对，导致验证不通过而无法建立主从同步关系。

[root@centos8 ~]#tail -f /var/log/redis/redis.log
3939:S 24 Oct 2020 16:13:57.552 # Server initialized
3939:S 24 Oct 2020 16:13:57.552 * DB loaded from disk: 0.000 seconds
3939:S 24 Oct 2020 16:13:57.552 * Ready to accept connections
3939:S 24 Oct 2020 16:13:57.554 * Connecting to MASTER 10.0.0.18:6379
3939:S 24 Oct 2020 16:13:57.554 * MASTER <-> REPLICA sync started
3939:S 24 Oct 2020 16:13:57.556 * Non blocking connect for SYNC fired the event.
3939:S 24 Oct 2020 16:13:57.558 * Master replied to PING, replication can continue...
3939:S 24 Oct 2020 16:13:57.559 # Unable to AUTH to MASTER: -ERR invalid password

不同的redis 大版本之间存在兼容性问题，比如：3和4，4和5之间，因此各master和slave之间必须保持版本一致

在开启了安全模式情况下，没有设置bind地址或者密码

#将bind 127.0.0.1注释掉以及没有设置密码
[root@master ~]#sed -ri "s/^(bind.*)/#\1/" /etc/redis.conf
[root@master ~]#systemctl restart redis
[root@master ~]#ss -ntl
State       Recv-Q       Send-Q               Local Address:Port               Peer Address:Port       
LISTEN      0            128                        0.0.0.0:22                      0.0.0.0:*          
LISTEN      0            100                      127.0.0.1:25                      0.0.0.0:*          
LISTEN      0            511                        0.0.0.0:6379                    0.0.0.0:*          
LISTEN      0            128                           [::]:22                         [::]:*          
LISTEN      0            100                          [::1]:25                         [::]:*

#在其它客户端连接10.0.0.8
[root@slave1 ~]#redis-cli -h 10.0.0.8 
10.0.0.8:6379> KEYS *
(error) DENIED Redis is running in protected mode because protected mode is enabled, no bind address was specified, no authentication password is requested to clients. In this mode connections are only accepted from the loopback interface. If you want to connect from external computers to Redis you may adopt one of the following solutions: 1) Just disable protected mode sending the command 'CONFIG SET protected-mode no' from the loopback interface by connecting to Redis from the same host the server is running, however MAKE SURE Redis is not publicly accessible from internet if you do so. Use CONFIG REWRITE to make this change permanent. 2) Alternatively you can just disable the protected mode by editing the Redis configuration file, and setting the protected mode option to 'no', and then restarting the server. 3) If you started the server manually just for testing, restart it with the '--protected-mode no' option. 4) Setup a bind address or an authentication password. NOTE: You only need to do one of the above things in order for the server to start accepting connections from the outside.

#本机登录
[root@master ~]#redis-cli 
127.0.0.1:6379> KEYS *
1) "key2"
2) "name"
3) "key1"

Sentinel进程是用于监控redis集群中Master主服务器工作的状态，在Master主 服务器发生故障的时候，可以实现Master和Slave服务器的切换，保证系统的高 可用，此功能在redis2.6+的版本已引用，Redis的哨兵模式到了2.8版本之后就 稳定了下来。一般在生产环境也建议使用Redis的2.8版本的以后版本

哨兵(Sentinel) 是一个分布式系统，可以在一个架构中运行多个哨兵 (sentinel)进程，这些进程使用流言协议(gossip protocols)来接收关于Master 主服务器是否下线的信息，并使用投票协议(Agreement Protocols)来决定是否 执行自动故障迁移,以及选择哪个Slave作为新的Master

每个哨兵(Sentinel)进程会向其它哨兵(Sentinel)、Master、Slave定时发送消 息，以确认对方是否”活”着，如果发现对方在指定配置时间(此项可配置)内未 得到回应，则暂时认为对方已离线，也就是所谓的”主观认为宕机” (主观:是 每个成员都具有的独自的而且可能相同也可能不同的意识)，英文名称： Subjective Down，简称SDOWN

有主观宕机，对应的有客观宕机。当“哨兵群”中的多数Sentinel进程在对 Master主服务器做出SDOWN的判断，并且通过SENTINEL is-master-down-by-addr 命令互相交流之后，得出的Master Server下线判断，这种方式就是“客观宕 机”(客观:是不依赖于某种意识而已经实际存在的一切事物)，英文名称是： Objectively Down， 简称 ODOWN

通过一定的vote算法，从剩下的slave从服务器节点中，选一台提升为Master服务器节点，然后自动修改相关配置，并开启故障转移（failover）

Sentinel 机制可以解决master和slave角色的自动切换问题，但单个 Master 的性能瓶颈问题无法解决,类似于MySQL中的MHA功能

Redis Sentinel中的Sentinel节点个数应该为大于等于3且最好为奇数

客户端初始化时连接的是Sentinel节点集合，不再是具体的Redis节点，但Sentinel只是配置中心不是代理。

Redis Sentinel 节点与普通redis 没有区别,要实现读写分离依赖于客户端程序

redis 3.0 之前版本中,生产环境一般使用哨兵模式,但3.0后推出redis cluster功能后,可以支持更大规模的生产环境

• 每10秒每个sentinel对master和slave执行info

  发现slave节点

  确认主从关系

• 每2秒每个sentinel通过master节点的channel交换信(pub/sub)

  通过sentinel_hello频道交互

  交互对节点的“看法”和自身信息

• 每1秒每个sentinel对其他sentinel和redis执行ping

哨兵的前提是已经实现了一个redis的主从复制的运行环境，从而实现一个一主两从基于哨兵的高可用redis架构

注意: master 的配置文件中masterauth 和slave 都必须相同

所有主从节点的redis.conf中关健配置

范例：

#在所有主从节点执行，这里以master为例
[root@master ~]#yum -y install redis
[root@master ~]#systemctl enable --now redis
#交互式执行
[root@master ~]#vim /etc/redis.conf
bind 0.0.0.0
masterauth "123456"
requirepass "123456"
#或者非交互执行，这里以master为例
[root@master ~]#sed -i -e 's/bind 127.0.0.1/bind 0.0.0.0/' -e 's/^# masterauth.*/masterauth centos/' -e 's/^# requirepass .*/requirepass centos/' /etc/redis.conf
[root@master ~]#echo -e "net.core.somaxconn = 1024\nvm.overcommit_memory = 1" >> /etc/sysctl.conf 
[root@master ~]#sysctl -p
net.core.somaxconn = 1024
vm.overcommit_memory = 1
[root@master ~]#echo never > /sys/kernel/mm/transparent_hugepage/enabled
[root@master ~]#echo "echo never > /sys/kernel/mm/transparent_hugepage/enabled" >> /etc/rc.d/rc.local 
[root@master ~]#chmod +x /etc/rc.d/rc.local 
[root@master ~]#systemctl restart redis

#在所有从节点执行，这里以salve1为例
[root@slave1 ~]#sed -ri "s/^# (replicaof).*/\1 10.0.0.8 6379/" /etc/redis.conf
[root@slave1 ~]#systemctl restart redis

master服务器状态

[root@master ~]#redis-cli -a centos
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:2
slave0:ip=10.0.0.18,port=6379,state=online,offset=112,lag=0
slave1:ip=10.0.0.28,port=6379,state=online,offset=112,lag=0
master_replid:4f93708e2b1ab6f3a47233db68cd99fc3db28409
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:112
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:112

查看slave1和slave2

1)在slave1上
[root@slave1 ~]#redis-cli -a centos
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:10.0.0.8
master_port:6379
master_link_status:up
master_last_io_seconds_ago:7
master_sync_in_progress:0
slave_repl_offset:350
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:4f93708e2b1ab6f3a47233db68cd99fc3db28409
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:350
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:350
2)在slave2上
[root@slave2 ~]#redis-cli -a centos
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:10.0.0.8
master_port:6379
master_link_status:up
master_last_io_seconds_ago:7
master_sync_in_progress:0
slave_repl_offset:434
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:4f93708e2b1ab6f3a47233db68cd99fc3db28409
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:434
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:85
repl_backlog_histlen:350

sentinel配置

Sentinel实际上是一个特殊的redis服务器,有些redis指令支持,但很多指令并不支持.默认监听在26379/tcp端口.

哨兵可以不和Redis服务器部署在一起，但一般部署在一起，所有redis节点使用相同的以下示例的配置文件

#如果是编译安装，在源码目录有sentinel.conf，复制到安装目录即可，如:/apps/redis/etc/sentinel.conf
[root@master ~]#grep -Ev "^(#|$)" /etc/redis-sentinel.conf 
port 26379
daemonize yes
pidfile /var/run/redis-sentinel.pid
logfile ""
dir /tmp    #工作目录

sentinel monitor mymaster <MASTER_IP> 6379 2        #指定当前mymaster集群中master服务器的地址和端口
#2为法定人数限制(quorum)，即有几个sentinel认为master down了就进行故障转移，一般此值是所有sentinel节点(一般总数是>=3的 奇数,如:3,5,7等)的一半以上的整数值，比如，总数是3，即3/2=1.5，取整为2,是master的ODOWN客观下线的依据

sentinel auth-pass <master-name> <password>     #mymaster集群中master的密码，注意此行要在上面行的下面

sentinel down-after-milliseconds mymaster 30000     #(SDOWN)判断mymaster集群中所有节点的主观下线的时间，单位：毫秒，建议3000

sentinel parallel-syncs mymaster 1      #发生故障转移后，同时向新master同步数据的slave数量，数字越小总同步时间越长，但可以减轻新master的负载压力

sentinel failover-timeout mymaster 180000       #所有slaves指向新的master所需的超时时间，单位：毫秒

sentinel deny-scripts-reconfig yes  #禁止修改脚本

logfile /var/log/redis/sentinel.log

三个哨兵服务器的配置都如下，以master为例：

[root@master ~]#sed -ri -e '/^logfile ""/d' -e "s/127.0.0.1/10.0.0.8/" -e "s/^# (sentinel auth-pass) <master-name> <password>/\1 mymaster centos/" -e "s/30000/3000/" /etc/redis-sentinel.conf
[root@master ~]#grep -Ev "^(#|$)" /etc/redis-sentinel.conf 
port 26379
daemonize no
pidfile /var/run/redis-sentinel.pid
dir /tmp
sentinel monitor mymaster 10.0.0.8 6379 2       #修改后的内容
sentinel auth-pass mymaster centos      #增加后的内容
sentinel down-after-milliseconds mymaster 3000      #修改后的内容
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 180000
sentinel deny-scripts-reconfig yes
logfile /var/log/redis/sentinel.log

三台哨兵服务器都要启动

#确保每个哨兵主机myid不同
1)在master上
[root@master ~]#systemctl enable --now redis-sentinel
[root@master ~]#grep myid /etc/redis-sentinel.conf 
sentinel myid 78af3e3a3edda463b4562c483bc5306ebdbba2fa

2)在slave1上
[root@slave1 ~]#systemctl enable --now redis-sentinel
[root@slave1 ~]#grep myid /etc/redis-sentinel.conf 
sentinel myid 03c56cc82c32d74c473caaec5422be9ed803035c
2)在slave2上
[root@slave2 ~]#systemctl enable --now redis-sentinel
[root@slave2 ~]#grep myid /etc/redis-sentinel.conf 
sentinel myid db9f04d90b5bc5fcb83f409592ce4273014c51dd

#以下内容在服务启动后自动生成，不需要修改
[root@master ~]#grep -Ev "^(#|$)" /etc/redis-sentinel.conf
......
sentinel myid 78af3e3a3edda463b4562c483bc5306ebdbba2fa
......
protected-mode no
supervised systemd
sentinel leader-epoch mymaster 0
sentinel known-replica mymaster 10.0.0.28 6379
sentinel known-replica mymaster 10.0.0.18 6379
sentinel known-sentinel mymaster 10.0.0.18 26379 03c56cc82c32d74c473caaec5422be9ed803035c
sentinel known-sentinel mymaster 10.0.0.28 26379 db9f04d90b5bc5fcb83f409592ce4273014c51dd

如果是编译安装,在所有哨兵服务器执行下面操作启动哨兵

#vim /apps/redis/etc/sentinel.conf
bind 0.0.0.0
port 26379
daemonize yes
pidfile "redis-sentinel.pid"
Logfile "sentinel_26379.log"
dir "/apps/redis/data"
sentinel monitor mymaster 10.0.0.8 6379 2
sentinel auth-pass mymaster 123456
sentinel down-after-milliseconds mymaster 15000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 180000
sentinel deny-scripts-reconfig yes

#/apps/redis/bin/redis-sentinel /apps/redis/etc/sentinel.conf

#在所有节点上验证哨兵端口，以master为例
[root@master ~]#ss -ntl
State       Recv-Q       Send-Q              Local Address:Port                Peer Address:Port       
LISTEN      0            128                       0.0.0.0:22                       0.0.0.0:*          
LISTEN      0            100                     127.0.0.1:25                       0.0.0.0:*          
LISTEN      0            511                       0.0.0.0:6379                     0.0.0.0:*          
LISTEN      0            511                       0.0.0.0:26379                    0.0.0.0:*          
LISTEN      0            128                          [::]:22                          [::]:*          
LISTEN      0            100                         [::1]:25                          [::]:*          
LISTEN      0            511                          [::]:26379                       [::]:*

master的哨兵日志

[root@master ~]#cat /var/log/redis/sentinel.log 
2074:X 24 Oct 2020 21:52:04.694 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
2074:X 24 Oct 2020 21:52:04.694 # Redis version=5.0.3, bits=64, commit=00000000, modified=0, pid=2074, just started
2074:X 24 Oct 2020 21:52:04.694 # Configuration loaded
2074:X 24 Oct 2020 21:52:04.694 * supervised by systemd, will signal readiness
2074:X 24 Oct 2020 21:52:04.697 * Running mode=sentinel, port=26379.
2074:X 24 Oct 2020 21:52:04.699 # Sentinel ID is c5325dd8405cf58245cc4febf1bbbcd6ea87e056
2074:X 24 Oct 2020 21:52:04.699 # +monitor master mymaster 10.0.0.8 6379 quorum 2
2074:X 24 Oct 2020 21:52:04.701 * +slave slave 10.0.0.18:6379 10.0.0.18 6379 @ mymaster 10.0.0.8 6379
2074:X 24 Oct 2020 21:52:04.703 * +slave slave 10.0.0.28:6379 10.0.0.28 6379 @ mymaster 10.0.0.8 6379
2074:X 24 Oct 2020 21:52:06.730 * +sentinel sentinel 56416b867d4e8dc45405261397b9b77d53bcefec 10.0.0.28 26379 @ mymaster 10.0.0.8 6379
2074:X 24 Oct 2020 21:52:06.778 * +sentinel sentinel 1fe5ef1c56e0cc263d594edae28f5321c33482b9 10.0.0.18 26379 @ mymaster 10.0.0.8 6379

slave的哨兵日志

#以slave1为例
[root@slave1 ~]#cat /var/log/redis/sentinel.log
7723:X 24 Oct 2020 21:12:28.455 * Removing the pid file.
7723:X 24 Oct 2020 21:12:28.455 # Sentinel is now ready to exit, bye bye...
7814:X 24 Oct 2020 21:12:28.537 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
7814:X 24 Oct 2020 21:12:28.538 # Redis version=5.0.3, bits=64, commit=00000000, modified=0, pid=7814, just started
7814:X 24 Oct 2020 21:12:28.538 # Configuration loaded
7814:X 24 Oct 2020 21:12:28.538 * supervised by systemd, will signal readiness
7814:X 24 Oct 2020 21:12:28.539 * Running mode=sentinel, port=26379.
7814:X 24 Oct 2020 21:12:28.539 # Sentinel ID is 03c56cc82c32d74c473caaec5422be9ed803035c
7814:X 24 Oct 2020 21:12:28.539 # +monitor master mymaster 10.0.0.8 6379 quorum 2

在sentinel状态中尤其是最后一行，涉及到masterIP是多少，有几个slave，有几个sentinels，必须是符合全部服务器数量

[root@master ~]#redis-cli -p 26379
127.0.0.1:26379> info sentinel
# Sentinel
sentinel_masters:1
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_failure_flags:0
master0:name=mymaster,status=ok,address=10.0.0.8:6379,slaves=2,sentinels=3      #两个slave，三个sentinel服务器，如果sentinels值不符合，检查myid可能冲突

[root@redis-master ~]#killall redis-server

查看各节点上哨兵信息：

[root@master ~]#redis-cli -a centos -p 26379
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:26379> info sentinel
# Sentinel
sentinel_masters:1
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_failure_flags:0
master0:name=mymaster,status=ok,address=10.0.0.18:6379,slaves=2,sentinels=3

故障转移时sentinel的信息：

[root@master ~]#cat /var/log/redis/sentinel.log
2490:X 24 Oct 2020 22:18:30.025 # +sdown slave 10.0.0.28:6379 10.0.0.28 6379 @ mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:18:36.154 # -sdown sentinel 56416b867d4e8dc45405261397b9b77d53bcefec 10.0.0.28 26379 @ mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:18:36.464 # -sdown slave 10.0.0.28:6379 10.0.0.28 6379 @ mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:18:59.384 # +sdown master mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:18:59.485 # +odown master mymaster 10.0.0.8 6379 #quorum 2/2
2490:X 24 Oct 2020 22:18:59.485 # +new-epoch 9
2490:X 24 Oct 2020 22:18:59.485 # +try-failover master mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:18:59.486 # +vote-for-leader c5325dd8405cf58245cc4febf1bbbcd6ea87e056 9
2490:X 24 Oct 2020 22:18:59.489 # 1fe5ef1c56e0cc263d594edae28f5321c33482b9 voted for c5325dd8405cf58245cc4febf1bbbcd6ea87e056 9
2490:X 24 Oct 2020 22:18:59.490 # 56416b867d4e8dc45405261397b9b77d53bcefec voted for c5325dd8405cf58245cc4febf1bbbcd6ea87e056 9
2490:X 24 Oct 2020 22:18:59.577 # +elected-leader master mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:18:59.577 # +failover-state-select-slave master mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:18:59.660 # +selected-slave slave 10.0.0.18:6379 10.0.0.18 6379 @ mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:18:59.660 * +failover-state-send-slaveof-noone slave 10.0.0.18:6379 10.0.0.18 6379 @ mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:18:59.718 * +failover-state-wait-promotion slave 10.0.0.18:6379 10.0.0.18 6379 @ mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:19:00.190 # +promoted-slave slave 10.0.0.18:6379 10.0.0.18 6379 @ mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:19:00.190 # +failover-state-reconf-slaves master mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:19:00.272 * +slave-reconf-sent slave 10.0.0.28:6379 10.0.0.28 6379 @ mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:19:00.608 # -odown master mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:19:00.609 * +slave-reconf-inprog slave 10.0.0.28:6379 10.0.0.28 6379 @ mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:19:01.614 * +slave-reconf-done slave 10.0.0.28:6379 10.0.0.28 6379 @ mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:19:01.665 # +failover-end master mymaster 10.0.0.8 6379
2490:X 24 Oct 2020 22:19:01.665 # +switch-master mymaster 10.0.0.8 6379 10.0.0.18 6379
2490:X 24 Oct 2020 22:19:01.666 * +slave slave 10.0.0.28:6379 10.0.0.28 6379 @ mymaster 10.0.0.18 6379
2490:X 24 Oct 2020 22:19:01.666 * +slave slave 10.0.0.8:6379 10.0.0.8 6379 @ mymaster 10.0.0.18 6379
2490:X 24 Oct 2020 22:19:04.687 # +sdown slave 10.0.0.8:6379 10.0.0.8 6379 @ mymaster 10.0.0.18 6379

故障转移后其它从节点redis.conf中的replicaof行的master IP会被修改

[root@slave2 ~]#grep "^replicaof" /etc/redis.conf
replicaof 10.0.0.18 6379

哨兵配置文件的sentinel monitor IP 同样也会被修改

[root@master ~]#grep "^[a-Z]" /etc/redis-sentinel.conf
port 26379
daemonize no
pidfile "/var/run/redis-sentinel.pid"
dir "/tmp"
sentinel myid c5325dd8405cf58245cc4febf1bbbcd6ea87e056
sentinel deny-scripts-reconfig yes
sentinel monitor mymaster 10.0.0.18 6379 2
sentinel down-after-milliseconds mymaster 3000
sentinel auth-pass mymaster centos
sentinel config-epoch mymaster 9
logfile "/var/log/redis/sentinel.log"
protected-mode no
supervised systemd
sentinel leader-epoch mymaster 9
sentinel known-replica mymaster 10.0.0.28 6379
sentinel known-replica mymaster 10.0.0.8 6379
sentinel known-sentinel mymaster 10.0.0.18 26379 1fe5ef1c56e0cc263d594edae28f5321c33482b9
sentinel known-sentinel mymaster 10.0.0.28 26379 56416b867d4e8dc45405261397b9b77d53bcefec
sentinel current-epoch 9

[root@slave1 ~]#grep "^[a-Z]" /etc/redis-sentinel.conf
port 26379
daemonize no
pidfile "/var/run/redis-sentinel.pid"
dir "/tmp"
sentinel myid 1fe5ef1c56e0cc263d594edae28f5321c33482b9
sentinel deny-scripts-reconfig yes
sentinel monitor mymaster 10.0.0.18 6379 2
sentinel down-after-milliseconds mymaster 3000
sentinel auth-pass mymaster centos
sentinel config-epoch mymaster 9
logfile "/var/log/redis/sentinel.log"
protected-mode no
supervised systemd
sentinel leader-epoch mymaster 9
sentinel known-replica mymaster 10.0.0.8 6379
sentinel known-replica mymaster 10.0.0.28 6379
sentinel known-sentinel mymaster 10.0.0.8 26379 c5325dd8405cf58245cc4febf1bbbcd6ea87e056
sentinel known-sentinel mymaster 10.0.0.28 26379 56416b867d4e8dc45405261397b9b77d53bcefec
sentinel current-epoch 9

[root@slave2 ~]#grep "^[a-Z]" /etc/redis-sentinel.conf
port 26379
daemonize no
pidfile "/var/run/redis-sentinel.pid"
dir "/tmp"
sentinel myid 56416b867d4e8dc45405261397b9b77d53bcefec
sentinel deny-scripts-reconfig yes
sentinel monitor mymaster 10.0.0.18 6379 2
sentinel down-after-milliseconds mymaster 3000
sentinel auth-pass mymaster centos
sentinel config-epoch mymaster 9
logfile "/var/log/redis/sentinel.log"
protected-mode no
supervised systemd
sentinel leader-epoch mymaster 9
sentinel known-replica mymaster 10.0.0.28 6379
sentinel known-replica mymaster 10.0.0.8 6379
sentinel known-sentinel mymaster 10.0.0.18 26379 1fe5ef1c56e0cc263d594edae28f5321c33482b9
sentinel known-sentinel mymaster 10.0.0.8 26379 c5325dd8405cf58245cc4febf1bbbcd6ea87e056
sentinel current-epoch 9

新的master 状态

[root@slave1 ~]#redis-cli -a centos 
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> info replication
# Replication
role:master     #提升为master
connected_slaves:1
slave0:ip=10.0.0.28,port=6379,state=online,offset=162015,lag=0
master_replid:d0986944509eefec498f58c3eef54240d373ce31
master_replid2:71aa5e09a5f6c2034a5e8f853e3ec0975d9d0ff3
master_repl_offset:162015
second_repl_offset:8732
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:162015

另一个slave指向新的master

[root@slave2 ~]#redis-cli -a centos
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:10.0.0.18   #指向新的master
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:196879
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:d0986944509eefec498f58c3eef54240d373ce31
master_replid2:71aa5e09a5f6c2034a5e8f853e3ec0975d9d0ff3
master_repl_offset:196879
second_repl_offset:8732
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:6851
repl_backlog_histlen:190029

#让原master恢复
[root@master ~]#systemctl start redis
#sentinel会自动修改下面行指向新的master
[root@master ~]#grep "^replicaof" /etc/redis.conf 
replicaof 10.0.0.18 6379

在原 master上观察状态

[root@master ~]#redis-cli -a centos
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:10.0.0.18
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:241800
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:d0986944509eefec498f58c3eef54240d373ce31
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:241800
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:216787
repl_backlog_histlen:25014

[root@master ~]#redis-cli -a centos -p 26379
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:26379> info replication
127.0.0.1:26379> info sentinel
# Sentinel
sentinel_masters:1
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_failure_flags:0
master0:name=mymaster,status=ok,address=10.0.0.18:6379,slaves=2,sentinels=3

观察新master上状态和日志

[root@slave1 ~]#redis-cli -a centos 
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:2
slave0:ip=10.0.0.28,port=6379,state=online,offset=261044,lag=1
slave1:ip=10.0.0.8,port=6379,state=online,offset=261044,lag=1
master_replid:d0986944509eefec498f58c3eef54240d373ce31
master_replid2:71aa5e09a5f6c2034a5e8f853e3ec0975d9d0ff3
master_repl_offset:261309
second_repl_offset:8732
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:261309

[root@slave1 ~]#cat /var/log/redis/sentinel.log
7529:X 24 Oct 2020 22:19:03.307 # +sdown slave 10.0.0.8:6379 10.0.0.8 6379 @ mymaster 10.0.0.18 6379
7529:X 24 Oct 2020 22:36:27.173 # -sdown slave 10.0.0.8:6379 10.0.0.8 6379 @ mymaster 10.0.0.18 6379

手动让主节点下线

sentinel failover <masterName>

范例: 手动故障转移

[root@master ~]#sed -ri "s/^(replica-priority).*/\1 10/" /etc/redis.conf
[root@master ~]#grep replica-priority /etc/redis.conf 
replica-priority 10 #指定优先级,值越小sentinel会优先将之选为新的master,默为值为100   

[root@master ~]#redis-cli -a centos -p 26379
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:26379> sentinel failover mymaster
OK
127.0.0.1:26379> info sentinel
# Sentinel
sentinel_masters:1
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_failure_flags:0
master0:name=mymaster,status=ok,address=10.0.0.8:6379,slaves=2,sentinels=3

Redis 官方客户端：https://redis.io/clients

假如三个主节点分别是：A，B，C三个节点，采用哈希槽(hash slot)的方式来分配16384个slot的活，它们三个节点分别承担的slot 区间可以是：

节点A覆盖：0-5460
节点B覆盖：5461-10922
节点C覆盖：10923-16383

Redis cluster的架构虽然解决了并发的问题，但是又引入了一个新的问题，每个Redis master的高可用如何解决？

那就是对每个master 节点都实现主从复制,从而实现 redis 高可用性

环境A：3台服务器，每台服务器启动6379和6380两个redis 服务实例，适用于测试环境

环境B：6台服务器，分别是三组master/slave，适用于生产环境

#集群节点
10.0.0.8
10.0.0.18
10.0.0.28
10.0.0.38
10.0.0.48
10.0.0.58
#预留服务器扩展使用
10.0.0.68
10.0.0.78

说明：Redis 5.X 和之前版本相比有很多变化，以下分别介绍两个版本5.X和4.X的配置

redis cluster 有多种部署方法

• 原生命令安装

  理解Redis Cluster架构

  生产环境不使用

• 官方工具安装

  高效、准确

  生产环境可以使用

• 自主研发 可以实现可视化的自动化部署

• 在所有节点安装redis,并配置开启cluster功能
• 各个节点执行meet,实现所有节点的相互通信
• 为各个master 节点指派槽位范围
• 指定各个节点的主从关系

1. 每个redis 节点采用相同的硬件配置、相同的密码、相同的redis版本
2. 所有redis服务器必须没有任何数据
3. 准备6台主机，地址如下：

10.0.0.8
10.0.0.18
10.0.0.28
10.0.0.38
10.0.0.48
10.0.0.58

所有6台主机都执行以下配置，以redis-node1为例

[root@redis-node1 ~]#yum -y install redis

• 每个节点都要修改redis.conf配置文件，必须都开启cluster功能的参数，这里以redis-node1为例

  [root@redis-node1 ~]#cat init.sh 
  #!/bin/bash
  
  sed -i -e "s/bind 127.0.0.1/bind 0.0.0.0/" -e "s/^#       
  masterauth.*/masterauth centos/" -e "s/^# requirepass .*/requirepass centos/" -e "/# cluster-enabled yes/a cluster-enabled yes" -e "/# cluster-config-file nodes-6379.conf/a cluster-config-file nodes-6379.conf" -e "/# cluster-require-full-coverage yes/c cluster-require-full-coverage no" /etc/redis.conf
  
  echo -e "net.core.somaxconn = 1024\nvm.overcommit_memory = 1" >> /etc/sysctl.conf 
  sysctl -p
  echo never > /sys/kernel/mm/transparent_hugepage/enabled
  echo "echo never > /sys/kernel/mm/transparent_hugepage/enabled" >> /etc/rc.d/rc.local 
  chmod +x /etc/rc.d/rc.local 
  systemctl enable --now redis
  

• 验证当前Redis服务状态：以redis-node1为例

  #开启了16379的cluster的端口，实际的端口=redis port + 10000
  [root@redis-node1 ~]#ss -ntl
  State       Recv-Q       Send-Q              Local Address:Port                   Peer Address:Port       
  LISTEN      0            128                       0.0.0.0:22                         0.0.0.0:*          
  LISTEN      0            100                     127.0.0.1:25                       0.0.0.0:*          
  LISTEN      0            511                       0.0.0.0:16379                    0.0.0.0:*          
  LISTEN      0            511                       0.0.0.0:6379                     0.0.0.0:*          
  LISTEN      0            128                          [::]:22                          [::]:*          
  LISTEN      0            100                         [::1]:25                          [::]:* 
  
  #注意：进程有[cluster]状态
  [root@redis-node1 ~]#ps aux | grep redis
  redis      2017  0.1  0.6  53524  5124 ?        Ssl  14:49   0:00 /usr/bin/redis-server 0.0.0.0:6379 [cluster]
  root       2151  0.0  0.1  12112   984 pts/0    S+   14:55   0:00 grep --color=auto redis
  

# redis-cli --cluster-replicas 1 表示每个master对应一个slave节点
[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning --cluster create 10.0.0.8:6379 10.0.0.18:6379 10.0.0.28:6379 10.0.0.38:6379 10.0.0.48:6379 10.0.0.58:6379 --cluster-replicas 1
>>> Performing hash slots allocation on 6 nodes...
Master[0] -> Slots 0 - 5460
Master[1] -> Slots 5461 - 10922
Master[2] -> Slots 10923 - 16383
Adding replica 10.0.0.38:6379 to 10.0.0.8:6379
Adding replica 10.0.0.48:6379 to 10.0.0.18:6379
Adding replica 10.0.0.58:6379 to 10.0.0.28:6379
M: c5fd06610cd05c760e3fcfb60ad3b4351ce6b309 10.0.0.8:6379
   slots:[0-5460] (5461 slots) master
M: 1cd30e11cc46cffa0e441c456a2ecf2645a72771 10.0.0.18:6379
   slots:[5461-10922] (5462 slots) master
M: 79643546e59ba0e88477e1678dda30c29113dc56 10.0.0.28:6379
   slots:[10923-16383] (5461 slots) master
S: cbb5606890cf491d23379e426c61f62fc3a0732e 10.0.0.38:6379
   replicates c5fd06610cd05c760e3fcfb60ad3b4351ce6b309
S: e1cb57392effcc88a76060104d131044224a8285 10.0.0.48:6379
   replicates 1cd30e11cc46cffa0e441c456a2ecf2645a72771
S: 4e42a7dacf7642810aa398817388e1f120649ba7 10.0.0.58:6379
   replicates 79643546e59ba0e88477e1678dda30c29113dc56
Can I set the above configuration? (type 'yes' to accept): yes
>>> Nodes configuration updated
>>> Assign a different config epoch to each node
>>> Sending CLUSTER MEET messages to join the cluster
Waiting for the cluster to join
...
>>> Performing Cluster Check (using node 10.0.0.8:6379)
M: c5fd06610cd05c760e3fcfb60ad3b4351ce6b309 10.0.0.8:6379
   slots:[0-5460] (5461 slots) master
   1 additional replica(s)
S: cbb5606890cf491d23379e426c61f62fc3a0732e 10.0.0.38:6379
   slots: (0 slots) slave
   replicates c5fd06610cd05c760e3fcfb60ad3b4351ce6b309
M: 1cd30e11cc46cffa0e441c456a2ecf2645a72771 10.0.0.18:6379
   slots:[5461-10922] (5462 slots) master
   1 additional replica(s)
S: 4e42a7dacf7642810aa398817388e1f120649ba7 10.0.0.58:6379
   slots: (0 slots) slave
   replicates 79643546e59ba0e88477e1678dda30c29113dc56
M: 79643546e59ba0e88477e1678dda30c29113dc56 10.0.0.28:6379
   slots:[10923-16383] (5461 slots) master
   1 additional replica(s)
S: e1cb57392effcc88a76060104d131044224a8285 10.0.0.48:6379
   slots: (0 slots) slave
   replicates 1cd30e11cc46cffa0e441c456a2ecf2645a72771
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

#观察以上结果，可以看到3组master/slave
master:10.0.0.8---slave:10.0.0.38
master:10.0.0.18---slave:10.0.0.48
master:10.0.0.28---slave:10.0.0.58

[root@redis-node1 ~]#redis-cli -h 10.0.0.8 -a centos --no-auth-warning -c info replication
# Replication
role:master
connected_slaves:1
slave0:ip=10.0.0.38,port=6379,state=online,offset=448,lag=1
master_replid:b357337835511dc0a4a8c39af088ede2366a898f
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:448
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:448

[root@redis-node2 ~]#redis-cli -h 10.0.0.18 -a centos --no-auth-warning info replication
# Replication
role:master
connected_slaves:1
slave0:ip=10.0.0.48,port=6379,state=online,offset=574,lag=0
master_replid:9cacaf57dddd73cfcd71b79e8d1c14202f11991c
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:574
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:574

[root@redis-node3 ~]#redis-cli -h 10.0.0.28 -a centos --no-auth-warning info replication
# Replication
role:master
connected_slaves:1
slave0:ip=10.0.0.58,port=6379,state=online,offset=644,lag=0
master_replid:b1f5dda97b2f7fe4bb07ffe61272bdb71e1d2cfa
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:644
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:644    

[root@redis-node4 ~]#redis-cli -h 10.0.0.38 -a centos --no-auth-warning info replication
# Replication
role:slave
master_host:10.0.0.8
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:728
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:b357337835511dc0a4a8c39af088ede2366a898f
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:728
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:728

[root@redis-node5 ~]#redis-cli -h 10.0.0.48 -a centos --no-auth-warning info replication
# Replication
role:slave
master_host:10.0.0.18
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:784
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:9cacaf57dddd73cfcd71b79e8d1c14202f11991c
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:784
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:784

[root@redis-node6 ~]#redis-cli -h 10.0.0.58 -a centos --no-auth-warning info replication
# Replication
role:slave
master_host:10.0.0.28
master_port:6379
master_link_status:up
master_last_io_seconds_ago:10
master_sync_in_progress:0
slave_repl_offset:812
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:b1f5dda97b2f7fe4bb07ffe61272bdb71e1d2cfa
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:812
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:812

范例: 查看指定master节点的slave节点信息

[root@redis-node1 ~]#redis-cli -a centos cluster nodes
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
cbb5606890cf491d23379e426c61f62fc3a0732e 10.0.0.38:6379@16379 slave c5fd06610cd05c760e3fcfb60ad3b4351ce6b309 0 1603610101333 4 connected
1cd30e11cc46cffa0e441c456a2ecf2645a72771 10.0.0.18:6379@16379 master - 0 1603610100000 2 connected 5461-10922
4e42a7dacf7642810aa398817388e1f120649ba7 10.0.0.58:6379@16379 slave 79643546e59ba0e88477e1678dda30c29113dc56 0 1603610100325 6 connected
79643546e59ba0e88477e1678dda30c29113dc56 10.0.0.28:6379@16379 master - 0 1603610099000 3 connected 10923-16383
e1cb57392effcc88a76060104d131044224a8285 10.0.0.48:6379@16379 slave 1cd30e11cc46cffa0e441c456a2ecf2645a72771 0 1603610099316 5 connected
c5fd06610cd05c760e3fcfb60ad3b4351ce6b309 10.0.0.8:6379@16379 myself,master - 0 1603610099000 1 connected 0-5460

#以下命令查看指定master节点的slave节点信息,其中79643546e59ba0e88477e1678dda30c29113dc56 为master中redis-node3节点的ID
[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning cluster slaves 79643546e59ba0e88477e1678dda30c29113dc56
1) "4e42a7dacf7642810aa398817388e1f120649ba7 10.0.0.58:6379@16379 slave 79643546e59ba0e88477e1678dda30c29113dc56 0 1603610299010 6 connected"

[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning cluster info
cluster_state:ok
cluster_slots_assigned:16384
cluster_slots_ok:16384
cluster_slots_pfail:0
cluster_slots_fail:0
cluster_known_nodes:6       #节点数
cluster_size:3      #3个集群
cluster_current_epoch:6
cluster_my_epoch:1
cluster_stats_messages_ping_sent:1003
cluster_stats_messages_pong_sent:1042
cluster_stats_messages_sent:2045
cluster_stats_messages_ping_received:1037
cluster_stats_messages_pong_received:1003
cluster_stats_messages_meet_received:5
cluster_stats_messages_received:2045

#查看任意节点的集群状态
[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning --cluster info 10.0.0.18:6379
10.0.0.18:6379 (1cd30e11...) -> 0 keys | 5462 slots | 1 slaves.
10.0.0.28:6379 (79643546...) -> 0 keys | 5461 slots | 1 slaves.
10.0.0.8:6379 (c5fd0661...) -> 0 keys | 5461 slots | 1 slaves.
[OK] 0 keys in 3 masters.
0.00 keys per slot on average.
[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning --cluster info 10.0.0.48:6379
10.0.0.8:6379 (c5fd0661...) -> 0 keys | 5461 slots | 1 slaves.
10.0.0.28:6379 (79643546...) -> 0 keys | 5461 slots | 1 slaves.
10.0.0.18:6379 (1cd30e11...) -> 0 keys | 5462 slots | 1 slaves.
[OK] 0 keys in 3 masters.
0.00 keys per slot on average.

[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning cluster nodes
cbb5606890cf491d23379e426c61f62fc3a0732e 10.0.0.38:6379@16379 slave c5fd06610cd05c760e3fcfb60ad3b4351ce6b309 0 1603610918394 4 connected
1cd30e11cc46cffa0e441c456a2ecf2645a72771 10.0.0.18:6379@16379 master - 0 1603610920412 2 connected 5461-10922
4e42a7dacf7642810aa398817388e1f120649ba7 10.0.0.58:6379@16379 slave 79643546e59ba0e88477e1678dda30c29113dc56 0 1603610919403 6 connected
79643546e59ba0e88477e1678dda30c29113dc56 10.0.0.28:6379@16379 master - 0 1603610920000 3 connected 10923-16383
e1cb57392effcc88a76060104d131044224a8285 10.0.0.48:6379@16379 slave 1cd30e11cc46cffa0e441c456a2ecf2645a72771 0 1603610918000 5 connected
c5fd06610cd05c760e3fcfb60ad3b4351ce6b309 10.0.0.8:6379@16379 myself,master - 0 1603610918000 1 connected 0-5460

[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning --cluster check 10.0.0.38:6379
10.0.0.18:6379 (1cd30e11...) -> 0 keys | 5462 slots | 1 slaves.
10.0.0.8:6379 (c5fd0661...) -> 0 keys | 5461 slots | 1 slaves.
10.0.0.28:6379 (79643546...) -> 0 keys | 5461 slots | 1 slaves.
[OK] 0 keys in 3 masters.
0.00 keys per slot on average.
>>> Performing Cluster Check (using node 10.0.0.38:6379)
S: cbb5606890cf491d23379e426c61f62fc3a0732e 10.0.0.38:6379
   slots: (0 slots) slave
   replicates c5fd06610cd05c760e3fcfb60ad3b4351ce6b309
M: 1cd30e11cc46cffa0e441c456a2ecf2645a72771 10.0.0.18:6379
   slots:[5461-10922] (5462 slots) master
   1 additional replica(s)
S: 4e42a7dacf7642810aa398817388e1f120649ba7 10.0.0.58:6379
   slots: (0 slots) slave
   replicates 79643546e59ba0e88477e1678dda30c29113dc56
M: c5fd06610cd05c760e3fcfb60ad3b4351ce6b309 10.0.0.8:6379
   slots:[0-5460] (5461 slots) master
   1 additional replica(s)
M: 79643546e59ba0e88477e1678dda30c29113dc56 10.0.0.28:6379
   slots:[10923-16383] (5461 slots) master
   1 additional replica(s)
S: e1cb57392effcc88a76060104d131044224a8285 10.0.0.48:6379
   slots: (0 slots) slave
   replicates 1cd30e11cc46cffa0e441c456a2ecf2645a72771
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

[root@redis-node1 ~]#yum -y install python3
[root@redis-node1 ~]#pip3 install redis-py-cluster
[root@redis-node1 ~]#cat redis_cluster_test.py 
#!/usr/bin/env python3
from rediscluster  import RedisCluster
startup_nodes = [
    {"host":"10.0.0.8", "port":6379},
    {"host":"10.0.0.18", "port":6379},
    {"host":"10.0.0.28", "port":6379},
    {"host":"10.0.0.38", "port":6379},
    {"host":"10.0.0.48", "port":6379},
    {"host":"10.0.0.58", "port":6379}
]
redis_conn= RedisCluster(startup_nodes=startup_nodes,password='centos', decode_responses=True)

for i in range(0, 10000):
    redis_conn.set('key'+str(i),'value'+str(i))
    print('key'+str(i)+':',redis_conn.get('key'+str(i)))

[root@redis-node1 ~]#chmod +x redis_cluster_test.py
[root@redis-node1 ~]#./redis_cluster_test.py
...省略...
key9994: value9994
key9995: value9995
key9996: value9996
key9997: value9997
key9998: value9998
key9999: value9999
[root@redis-node1 ~]#redis-cli -a centos -h 10.0.0.8
127.0.0.1:6379> DBSIZE
(integer) 3333
127.0.0.1:6379> get key1
(error) MOVED 9189 10.0.0.18:6379
127.0.0.1:6379> get key2
"value2"
127.0.0.1:6379> get key3
"value3"
127.0.0.1:6379> KEYS *
...省略...
3330) "key8339"
3331) "key6248"
3332) "key5454"
3333) "key3664"

[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning -h 10.0.0.18 dbsize
(integer) 3341
[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning -h 10.0.0.18 get key1
"value1"
[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning -h 10.0.0.28 dbsize
(integer) 3330
[root@redis-node1 ~]#redis-cli -a centos --no-auth-warning -h 10.0.0.28 get key4
"value4"

#模拟node3节点出故障,需要相应的数秒故障转移时间
[root@redis-node3 ~]#tail -f /var/log/redis/redis.log 
[root@redis-node3 ~]#redis-cli -a centos --no-auth-warning
127.0.0.1:6379> shutdown
not connected> exit
[root@redis-node3 ~]#ss -ntl
State       Recv-Q       Send-Q               Local Address:Port               Peer Address:Port       
LISTEN      0            128                        0.0.0.0:22                      0.0.0.0:*          
LISTEN      0            128                           [::]:22                         [::]:*

[root@redis-node3 ~]#redis-cli -a centos --no-auth-warning --cluster info 10.0.0.8:6379
Could not connect to Redis at 10.0.0.28:6379: Connection refused
10.0.0.8:6379 (c5fd0661...) -> 3333 keys | 5461 slots | 1 slaves.
10.0.0.18:6379 (1cd30e11...) -> 3341 keys | 5462 slots | 1 slaves.
10.0.0.58:6379 (4e42a7da...) -> 3330 keys | 5461 slots | 0 slaves.      #10.0.0.58为新的master
[OK] 10004 keys in 3 masters.
0.61 keys per slot on average.

[root@redis-node3 ~]#redis-cli -a centos --no-auth-warning --cluster check 10.0.0.8:6379
Could not connect to Redis at 10.0.0.28:6379: Connection refused
10.0.0.8:6379 (c5fd0661...) -> 3333 keys | 5461 slots | 1 slaves.
10.0.0.18:6379 (1cd30e11...) -> 3341 keys | 5462 slots | 1 slaves.
10.0.0.58:6379 (4e42a7da...) -> 3330 keys | 5461 slots | 0 slaves.
[OK] 10004 keys in 3 masters.
0.61 keys per slot on average.
>>> Performing Cluster Check (using node 10.0.0.8:6379)
M: c5fd06610cd05c760e3fcfb60ad3b4351ce6b309 10.0.0.8:6379
   slots:[0-5460] (5461 slots) master
   1 additional replica(s)
S: cbb5606890cf491d23379e426c61f62fc3a0732e 10.0.0.38:6379
   slots: (0 slots) slave
   replicates c5fd06610cd05c760e3fcfb60ad3b4351ce6b309
M: 1cd30e11cc46cffa0e441c456a2ecf2645a72771 10.0.0.18:6379
   slots:[5461-10922] (5462 slots) master
   1 additional replica(s)
M: 4e42a7dacf7642810aa398817388e1f120649ba7 10.0.0.58:6379
   slots:[10923-16383] (5461 slots) master
S: e1cb57392effcc88a76060104d131044224a8285 10.0.0.48:6379
   slots: (0 slots) slave
   replicates 1cd30e11cc46cffa0e441c456a2ecf2645a72771
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

[root@redis-node3 ~]#redis-cli -a centos --no-auth-warning -h 10.0.0.58
10.0.0.58:6379> info replication
# Replication
role:master
connected_slaves:0
master_replid:f24aaee34b6062bcef89618129a13cdea0f37f04
master_replid2:b1f5dda97b2f7fe4bb07ffe61272bdb71e1d2cfa
master_repl_offset:141005
second_repl_offset:141006
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:141005

#恢复故障节点node3
[root@redis-node3 ~]#systemctl start redis

#查看自动生成的配置文件，可以查看node3自动生成slave节点
[root@redis-node3 ~]#cat /var/lib/redis/nodes-6379.conf 
79643546e59ba0e88477e1678dda30c29113dc56 10.0.0.28:6379@16379 myself,slave 4e42a7dacf7642810aa398817388e1f120649ba7 0 1603613511309 3 connected
e1cb57392effcc88a76060104d131044224a8285 10.0.0.48:6379@16379 slave 1cd30e11cc46cffa0e441c456a2ecf2645a72771 0 1603613511329 5 connected
4e42a7dacf7642810aa398817388e1f120649ba7 10.0.0.58:6379@16379 master - 0 1603613511329 7 connected 10923-16383
c5fd06610cd05c760e3fcfb60ad3b4351ce6b309 10.0.0.8:6379@16379 master - 0 1603613511330 1 connected 0-5460
1cd30e11cc46cffa0e441c456a2ecf2645a72771 10.0.0.18:6379@16379 master - 0 1603613511330 2 connected 5461-10922
cbb5606890cf491d23379e426c61f62fc3a0732e 10.0.0.38:6379@16379 slave c5fd06610cd05c760e3fcfb60ad3b4351ce6b309 0 1603613511330 4 connected
vars currentEpoch 7 lastVoteEpoch 0

[root@redis-node3 ~]#redis-cli -a centos --no-auth-warning -h 10.0.0.58
10.0.0.58:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=10.0.0.28,port=6379,state=online,offset=142559,lag=1
master_replid:f24aaee34b6062bcef89618129a13cdea0f37f04
master_replid2:b1f5dda97b2f7fe4bb07ffe61272bdb71e1d2cfa
master_repl_offset:142559
second_repl_offset:141006
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:142559
10.0.0.58:6379> 

1. 每个redis 节点采用相同的硬件配置、相同的密码、相同的redis版本
2. 所有redis服务器必须没有任何数据

3. 准备3台CentOS 7 主机，以编译安装好redis，各启动两个redis实例，分别使用6379和6380端口，从而模拟实现6台redis实例

   10.0.0.7:6379|6380
   10.0.0.17:6379|6380
   10.0.0.27:6379|6380
   

范例：6个物理节点环境的基于脚本安装后批量修改配置

[root@centos7 ~]#sed -i -e '/^# masterauth/a masterauth 123456' -e '/# clusterenabled
yes/a cluster-enabled yes' -e '/# cluster-config-file nodes-6379.conf/a
cluster-config-file nodes-6379.conf' -e '/cluster-require-full-coverage yes/c
cluster-require-full-coverage no' /apps/redis/etc/redis.conf

[root@centos7 ~]#grep '^[^#]' /apps/redis/etc/redis.conf
bind 0.0.0.0
protected-mode yes
port 6379
tcp-backlog 511
timeout 0
tcp-keepalive 300
daemonize no
supervised no
pidfile /apps/redis/run/redis_6379.pid
loglevel notice
logfile /apps/redis/log/redis-6379.log
databases 16
always-show-logo yes
save 900 1
save 300 10
save 60 10000
stop-writes-on-bgsave-error yes
rdbcompression yes
rdbchecksum yes
dbfilename dump.rdb
dir /apps/redis/data/
masterauth 123456
slave-serve-stale-data yes
slave-read-only yes
repl-diskless-sync no
repl-diskless-sync-delay 5
repl-disable-tcp-nodelay no
slave-priority 100
requirepass 123456
lazyfree-lazy-eviction no
lazyfree-lazy-expire no
lazyfree-lazy-server-del no
slave-lazy-flush no
appendonly no
appendfilename "appendonly.aof"
appendfsync everysec
no-appendfsync-on-rewrite no
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb
aof-load-truncated yes
aof-use-rdb-preamble no
lua-time-limit 5000
cluster-enabled yes
cluster-config-file nodes-6379.conf
cluster-require-full-coverage no
slowlog-log-slower-than 10000
slowlog-max-len 128
latency-monitor-threshold 0
notify-keyspace-events ""
hash-max-ziplist-entries 512
hash-max-ziplist-value 64
list-max-ziplist-size -2
list-compress-depth 0
set-max-intset-entries 512
zset-max-ziplist-entries 128
zset-max-ziplist-value 64
hll-sparse-max-bytes 3000
activerehashing yes
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit slave 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60
hz 10
aof-rewrite-incremental-fsync yes

准备6个实例：在三个主机上重复下面的操作

范例：3个节点实现6个实例

#在三台主机上都编译安装redis，以node1为例
[root@redis-node1 ~]# yum -y install gcc jemalloc-devel
[root@redis-node1 ~]# cd /usr/local/src/
[root@redis-node1 src]# wget http://download.redis.io/releases/redis-4.0.14.tar.gz
[root@redis-node1 src]# tar xf redis-4.0.14.tar.gz
[root@redis-node1 src]# cd redis-4.0.14
[root@redis-node1 redis-4.0.14]# make PREFIX=/apps/redis install

#准备相关文件和目录
[root@redis-node1 redis-4.0.14]# ln -s /apps/redis/bin/* /usr/bin/
[root@redis-node1 redis-4.0.14]# mkdir -p /apps/redis/{etc,log,run,data}
[root@redis-node1 redis-4.0.14]# cp redis.conf /apps/redis/etc/

#准备用户
[root@redis-node1 redis-4.0.14]# cd
[root@redis-node1 ~]# useradd -r -s /sbin/nologin redis

#配置权限和相关优化配置
[root@redis-node1 ~]# chown -R redis.redis /apps/redis
[root@redis-node1 ~]# cat >> /etc/sysctl.conf <<EOF
> net.core.somaxconn = 1024
> vm.overcommit_memory = 1
> EOF
[root@redis-node1 ~]# sysctl -p
[root@redis-node1 ~]# echo 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' >> /etc/rc.d/rc.local
[root@redis-node1 ~]# chmod +x /etc/rc.d/rc.local
[root@redis-node1 ~]# /etc/rc.d/rc.local

#准备service文件
[root@redis-node1 ~]# cat > /usr/lib/systemd/system/redis.service <<EOF
> [Unit]
> Description=Redis persistent key-value database
> After=network.target
> 
> [Service]
> ExecStart=/apps/redis/bin/redis-server /apps/redis/etc/redis.conf --supervised systemd
> ExecStop=/bin/kill -s QUIT \$MAINPID
> Type=notify
> User=redis
> Group=redis
> RuntimeDirectory=redis
> RuntimeDirectoryMode=0755
> 
> [Install]
> WantedBy=multi-user.target
> EOF

[root@redis-node1 ~]# systemctl daemon-reload
[root@redis-node1 ~]# systemctl enable --now redis

#准备6379的实例配置文件
[root@redis-node1 ~]# systemctl stop redis
[root@redis-node1 ~]# cd /apps/redis/etc
[root@redis-node1 etc]# sed -i.bak -e 's/bind 127.0.0.1/bind 0.0.0.0/' -e '/^# masterauth/a masterauth 123456' -e '/# requirepass/a requirepass 123456' -e '/# cluster-enabled yes/a cluster-enabled yes' -e '/# cluster-config-file nodes-6379.conf/a cluster-config-file nodes-6379.conf' -e 's/^dir .*/dir \/apps\/redis\/data/' -e '/appendonly no/c appendonly yes' -e '/logfile ""/c logfile "/apps/redis/log/redis-6379.log"' -e '/^pidfile .*/c pidfile /apps/redis/run/redis_6379.pid' /apps/redis/etc/redis.conf

#准备6380端口的实例的配置文件
[root@redis-node1 etc]# cp -a redis.conf redis6380.conf
[root@redis-node1 etc]# sed -i.bak -e 's/6379/6380/' -e 's/dbfilename dump\.rdb/dbfilename dump6380.rdb/' -e 's/appendfilename "appendonly\.aof"/appendfilename "appendonly6380.aof"/' /apps/redis/etc/redis6380.conf

#准备服务文件
[root@redis-node1 etc]# cp /lib/systemd/system/redis.service /lib/systemd/system/redis6380.service
[root@redis-node1 etc]# sed -i 's/redis.conf/redis6380.conf/' /lib/systemd/system/redis6380.service

#启动服务，查看到端口都打开
[root@redis-node1 etc]# systemctl daemon-reload
[root@redis-node1 etc]# systemctl enable --now redis redis6380
Created symlink from /etc/systemd/system/multi-user.target.wants/redis6380.service to /usr/lib/systemd/system/redis6380.service.
[root@redis-node1 etc]# ss -ntl
State       Recv-Q Send-Q      Local Address:Port                     Peer Address:Port              
LISTEN      0      100             127.0.0.1:25                                  *:*                  
LISTEN      0      511                     *:16379                               *:*                  
LISTEN      0      511                     *:16380                               *:*                  
LISTEN      0      511                     *:6379                                *:*                  
LISTEN      0      511                     *:6380                                *:*                  
LISTEN      0      128                     *:22                                  *:*                  
LISTEN      0      100                 [::1]:25                               [::]:*                  
LISTEN      0      128                  [::]:22                               [::]:* 

[root@redis-node1 etc]# ps -aux | grep redis
redis      4681  0.0  0.3 145416  3024 ?        Ssl  17:25   0:00 /apps/redis/bin/redis-server 0.0.0.0:6379 [cluster]
redis      4682  0.0  0.3 145416  3024 ?        Ssl  17:25   0:00 /apps/redis/bin/redis-server 0.0.0.0:6380 [cluster]
root       4901  0.0  0.0 112812   972 pts/0    S+   17:27   0:00 grep --color=auto redis

[root@redis-node1 ~]# tree /apps/redis
/apps/redis
├── bin
│   ├── redis-benchmark
│   ├── redis-check-aof
│   ├── redis-check-rdb
│   ├── redis-cli
│   ├── redis-sentinel -> redis-server
│   └── redis-server
├── data
│   ├── appendonly6380.aof
│   ├── appendonly.aof
│   ├── nodes-6379.conf
│   └── nodes-6380.conf
├── etc
│   ├── redis6380.conf
│   ├── redis6380.conf.bak
│   ├── redis.conf
│   └── redis.conf.bak
├── log
│   ├── redis-6379.log
│   └── redis-6380.log
└── run
    ├── redis_6379.pid
    └── redis_6380.pid

5 directories, 18 files

Redis 3和 4版本需要使用到集群管理工具redis-trib.rb，这个工具是redis官方推出的管理redis集群的工具，集成在redis的源码src目录下，是基于redis提供的集群命令封装成简单、便捷、实用的操作工具，redis-trib.rb是redis作者用ruby开发完成的，centos 7 系统yum安装的ruby存在版本较低问题，如下：

[root@redis-node1 ~]# find / -name redis-trib.rb 
/usr/local/src/redis-4.0.14/src/redis-trib.rb
[root@redis-node1 ~]# cp /usr/local/src/redis-4.0.14/src/redis-trib.rb /usr/bin/
[root@redis-node1 ~]# redis-trib.rb     #缺少ruby环境无法运行rb脚本
/usr/bin/env: ruby: No such file or directory

#CentOS 7带的ruby版本过低,无法运行上面ruby脚本,需要安装2.3以上版本,安装rubygems依赖ruby自动安装
[root@redis-node1 ~]# yum -y install rubygems
[root@redis-node1 ~]# gem install redis #gem相当于python的pip和linux的yum
Fetching: redis-4.2.2.gem (100%)
ERROR:  Error installing redis:
    redis requires Ruby version >= 2.3.0.

解决ruby版本较低问题：

[root@redis-node1 ~]# yum -y install gcc openssl-devel zlib-devel
[root@redis-node1 ~]# wget https://cache.ruby-lang.org/pub/ruby/2.5/ruby-2.5.5.tar.gz
[root@redis-node1 ~]# tar xf ruby-2.5.5.tar.gz
[root@redis-node1 ~]# cd ruby-2.5.5
[root@redis-node1 ruby-2.5.5]#./configure
[root@redis-node1 ruby-2.5.5]# make -j 2 && make install
[root@redis-node1 ruby-2.5.5]# which ruby
/usr/local/bin/ruby
[root@redis-node1 ruby-2.5.5]# ruby -v
ruby 2.5.5p157 (2019-03-15 revision 67260) [x86_64-linux]
[root@redis-node1 ruby-2.5.5]# exit #注意需要重新登录，否则无法运行

redis-trib.rb仍无法运行 报错

[root@redis-node1 ~]# redis-trib.rb -h
Traceback (most recent call last):
    2: from /usr/bin/redis-trib.rb:25:in `<main>'
    1: from /usr/local/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'
/usr/local/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require': cannot load such file -- redis (LoadError)

解决上述错误：

[root@redis-node1 ~]# gem install redis -v 4.1.3    #注意需要重新登录在执行，否则无法识别到新ruby版本
Fetching: redis-4.1.3.gem (100%)
Successfully installed redis-4.1.3
Parsing documentation for redis-4.1.3
Installing ri documentation for redis-4.1.3
Done installing documentation for redis after 1 seconds
1 gem installed
[root@redis-node1 ~]# exit

#gem uninstall redis 可以卸载已安装好的redis模块

如果无法在线安装，可以下载redis模块安装包离线安装

#https://rubygems.org/gems/redis #先下载redis模块安装包
[root@redis-node1 ~]#gem install -l redis-4.1.3.gem #安装redis模块

[root@redis-node1 ~]# redis-trib.rb
Usage: redis-trib <command> <options> <arguments ...>

  create          host1:port1 ... hostN:portN   #创建集群
                  --replicas <arg>  #指定每个master的副本数量,即对应slave数量,一般为1
  check           host:port #检查集群信息
  info            host:port #查看集群主机信息
  fix             host:port #修复集群
                  --timeout <arg>
  reshard         host:port #在线热迁移集群指定主机的slots数据
                  --from <arg>
                  --to <arg>
                  --slots <arg>
                  --yes
                  --timeout <arg>
                  --pipeline <arg>
  rebalance       host:port #平衡集群中各主机的slot数量
                  --weight <arg>
                  --auto-weights
                  --use-empty-masters
                  --timeout <arg>
                  --simulate
                  --pipeline <arg>
                  --threshold <arg>
  add-node        new_host:new_port existing_host:existing_port #添加主机到集群
                  --slave
                  --master-id <arg>
  del-node        host:port node_id #删除主机
  set-timeout     host:port milliseconds    #设置节点的超时时间
  call            host:port command arg arg .. arg  #在集群上的所有节点上执行命令
  import          host:port #导入外部redis服务器的数据到当前集群
                  --from <arg>
                  --copy
                  --replace
  help            (show this help)

For check, fix, reshard, del-node, set-timeout you can specify the host and port of any working node in the cluster.

#修改redis-trib.rb连接redis的密码
[root@redis-node1 ~]# vim /usr/local/lib/ruby/gems/2.5.0/gems/redis-4.1.3/lib/redis/client.rb

#确保3台主机6个实例都启动状态
[root@redis-node1 ~]# systemctl is-active redis redis6380
active
active
[root@redis-node2 ~]# systemctl is-active redis redis6380
active
active
[root@redis-node3 ~]# systemctl is-active redis redis6380
active
active

#在第一个主机上node1上执行下面操作
#--replicas 1 表示每个master 分配一个 slave 节点，前3个节点自动划分为master，后面都为slave节点
[root@redis-node1 ~]# redis-trib.rb create --replicas 1 10.0.0.7:6379 10.0.0.17:6379 10.0.0.27:6379 10.0.0.7:6380 10.0.0.17:6380 10.0.0.27:6380
>>> Creating cluster
>>> Performing hash slots allocation on 6 nodes...
Using 3 masters:
10.0.0.7:6379
10.0.0.17:6379
10.0.0.27:6379
Adding replica 10.0.0.17:6380 to 10.0.0.7:6379
Adding replica 10.0.0.27:6380 to 10.0.0.17:6379
Adding replica 10.0.0.7:6380 to 10.0.0.27:6379
M: 05d5695bdc82b2d461187ad1949def1ca402f58e 10.0.0.7:6379
   slots:0-5460 (5461 slots) master
M: ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592 10.0.0.17:6379
   slots:5461-10922 (5462 slots) master
M: ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94 10.0.0.27:6379
   slots:10923-16383 (5461 slots) master
S: e09ff1ee128352c3fa912c2ce865ffcb6b9a3e69 10.0.0.7:6380
   replicates ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94
S: 581851395649571f780989f6738a5d423f961228 10.0.0.17:6380
   replicates 05d5695bdc82b2d461187ad1949def1ca402f58e
S: 6e2b44ae14bee63df6d14637dc25f7873df6c5c3 10.0.0.27:6380
   replicates ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592
Can I set the above configuration? (type 'yes' to accept): yes
>>> Nodes configuration updated
>>> Assign a different config epoch to each node
>>> Sending CLUSTER MEET messages to join the cluster
Waiting for the cluster to join...
>>> Performing Cluster Check (using node 10.0.0.7:6379)
M: 05d5695bdc82b2d461187ad1949def1ca402f58e 10.0.0.7:6379
   slots:0-5460 (5461 slots) master
   1 additional replica(s)
S: 6e2b44ae14bee63df6d14637dc25f7873df6c5c3 10.0.0.27:6380
   slots: (0 slots) slave
   replicates ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592
M: ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592 10.0.0.17:6379
   slots:5461-10922 (5462 slots) master
   1 additional replica(s)
S: 581851395649571f780989f6738a5d423f961228 10.0.0.17:6380
   slots: (0 slots) slave
   replicates 05d5695bdc82b2d461187ad1949def1ca402f58e
M: ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94 10.0.0.27:6379
   slots:10923-16383 (5461 slots) master
   1 additional replica(s)
S: e09ff1ee128352c3fa912c2ce865ffcb6b9a3e69 10.0.0.7:6380
   slots: (0 slots) slave
   replicates ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

如果有之前的操作导致Redis集群创建报错，则执行清空数据和集群命令

127.0.0.1:6379> FLUSHALL
OK
127.0.0.1:6379> cluster reset
OK

自动生成配置文件记录master/slave对应关系

[root@redis-node1 ~]# cat /apps/redis/data/nodes-6379.conf 
6e2b44ae14bee63df6d14637dc25f7873df6c5c3 10.0.0.27:6380@16380 slave ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592 0 1603623843000 6 connected
ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592 10.0.0.17:6379@16379 master - 0 1603623842109 2 connected 5461-10922
581851395649571f780989f6738a5d423f961228 10.0.0.17:6380@16380 slave 05d5695bdc82b2d461187ad1949def1ca402f58e 0 1603623844124 5 connected
05d5695bdc82b2d461187ad1949def1ca402f58e 10.0.0.7:6379@16379 myself,master - 0 1603623840000 1 connected 0-5460
ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94 10.0.0.27:6379@16379 master - 0 1603623843115 3 connected 10923-16383
e09ff1ee128352c3fa912c2ce865ffcb6b9a3e69 10.0.0.7:6380@16380 slave ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94 0 1603623842000 4 connected
vars currentEpoch 6 lastVoteEpoch 0

查看状态

[root@redis-node1 ~]# redis-trib.rb info 10.0.0.7:6379
10.0.0.7:6379 (05d5695b...) -> 0 keys | 5461 slots | 1 slaves.
10.0.0.17:6379 (ebe1c9d8...) -> 0 keys | 5462 slots | 1 slaves.
10.0.0.27:6379 (ce0a9bbc...) -> 0 keys | 5461 slots | 1 slaves.
[OK] 0 keys in 3 masters.
0.00 keys per slot on average.

[root@redis-node1 ~]# redis-trib.rb info 10.0.0.7:6379
10.0.0.7:6379 (05d5695b...) -> 0 keys | 5461 slots | 1 slaves.
10.0.0.17:6379 (ebe1c9d8...) -> 0 keys | 5462 slots | 1 slaves.
10.0.0.27:6379 (ce0a9bbc...) -> 0 keys | 5461 slots | 1 slaves.
[OK] 0 keys in 3 masters.
0.00 keys per slot on average.
[root@redis-node1 ~]# redis-trib.rb check 10.0.0.7:6379
>>> Performing Cluster Check (using node 10.0.0.7:6379)
M: 05d5695bdc82b2d461187ad1949def1ca402f58e 10.0.0.7:6379
   slots:0-5460 (5461 slots) master
   1 additional replica(s)
S: 6e2b44ae14bee63df6d14637dc25f7873df6c5c3 10.0.0.27:6380
   slots: (0 slots) slave
   replicates ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592
M: ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592 10.0.0.17:6379
   slots:5461-10922 (5462 slots) master
   1 additional replica(s)
S: 581851395649571f780989f6738a5d423f961228 10.0.0.17:6380
   slots: (0 slots) slave
   replicates 05d5695bdc82b2d461187ad1949def1ca402f58e
M: ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94 10.0.0.27:6379
   slots:10923-16383 (5461 slots) master
   1 additional replica(s)
S: e09ff1ee128352c3fa912c2ce865ffcb6b9a3e69 10.0.0.7:6380
   slots: (0 slots) slave
   replicates ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

[root@redis-node1 ~]# redis-cli -a 123456 
Warning: Using a password with '-a' option on the command line interface may not be safe.
127.0.0.1:6379> cluster info
cluster_state:ok
cluster_slots_assigned:16384
cluster_slots_ok:16384
cluster_slots_pfail:0
cluster_slots_fail:0
cluster_known_nodes:6
cluster_size:3
cluster_current_epoch:6
cluster_my_epoch:1
cluster_stats_messages_ping_sent:491
cluster_stats_messages_pong_sent:521
cluster_stats_messages_sent:1012
cluster_stats_messages_ping_received:516
cluster_stats_messages_pong_received:491
cluster_stats_messages_meet_received:5
cluster_stats_messages_received:1012

[root@redis-node1 ~]# redis-cli -a 123456 -p 6379 cluster nodes
Warning: Using a password with '-a' option on the command line interface may not be safe.
6e2b44ae14bee63df6d14637dc25f7873df6c5c3 10.0.0.27:6380@16380 slave ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592 0 1603624406489 6 connected
ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592 10.0.0.17:6379@16379 master - 0 1603624405479 2 connected 5461-10922
581851395649571f780989f6738a5d423f961228 10.0.0.17:6380@16380 slave 05d5695bdc82b2d461187ad1949def1ca402f58e 0 1603624404000 5 connected
05d5695bdc82b2d461187ad1949def1ca402f58e 10.0.0.7:6379@16379 myself,master - 0 1603624405000 1 connected 0-5460
ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94 10.0.0.27:6379@16379 master - 0 1603624404474 3 connected 10923-16383
e09ff1ee128352c3fa912c2ce865ffcb6b9a3e69 10.0.0.7:6380@16380 slave ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94 0 1603624405000 4 connected

[root@redis-node1 ~]# redis-cli -a 123456 -p 6379 info replication
Warning: Using a password with '-a' option on the command line interface may not be safe.
# Replication
role:master
connected_slaves:1
slave0:ip=10.0.0.17,port=6380,state=online,offset=854,lag=0
master_replid:c4576364f25c85892c92feabca39bd8a9b779172
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:854
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:854

[root@redis-node1 ~]# redis-cli -a 123456 -p 6380 info replication
Warning: Using a password with '-a' option on the command line interface may not be safe.
# Replication
role:slave
master_host:10.0.0.27
master_port:6379
master_link_status:up
master_last_io_seconds_ago:6
master_sync_in_progress:0
slave_repl_offset:924
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:433df0468e1deb202ba93040743ab4ff7e38cf21
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:924
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:924

[root@redis-node1 ~]# yum -y install python3
[root@redis-node1 ~]# pip3 install redis-py-cluster
[root@redis-node1 ~]# cat redis_cluster_test.py 
#!/usr/bin/env python3
from rediscluster  import RedisCluster
startup_nodes = [
    {"host":"10.0.0.7", "port":6379},
    {"host":"10.0.0.17", "port":6379},
    {"host":"10.0.0.27", "port":6379},
    {"host":"10.0.0.37", "port":6379},
    {"host":"10.0.0.47", "port":6379},
    {"host":"10.0.0.57", "port":6379}
]
redis_conn= RedisCluster(startup_nodes=startup_nodes,password='123456', decode_responses=True)

for i in range(0, 10000):
    redis_conn.set('key'+str(i),'value'+str(i))
    print('key'+str(i)+':',redis_conn.get('key'+str(i)))

[root@redis-node1 ~]# chmod +x redis_cluster_test.py 
[root@redis-node1 ~]# ./redis_cluster_test.py
...省略...
key9997: value9997
key9998: value9998
key9999: value9999

验证脚本写入的状态

[root@redis-node1 ~]# redis-cli -a 123456 -h 10.0.0.7 dbsize
Warning: Using a password with '-a' option on the command line interface may not be safe.
(integer) 3331
[root@redis-node1 ~]# redis-cli -a 123456 -h 10.0.0.17 dbsize
Warning: Using a password with '-a' option on the command line interface may not be safe.
(integer) 3340
[root@redis-node1 ~]# redis-cli -a 123456 -h 10.0.0.27 dbsize
Warning: Using a password with '-a' option on the command line interface may not be safe.
(integer) 3329
[root@redis-node1 ~]# redis-cli -a 123456 get key1
Warning: Using a password with '-a' option on the command line interface may not be safe.
(error) MOVED 9189 10.0.0.17:6379
[root@redis-node1 ~]# redis-cli -a 123456 get key2
Warning: Using a password with '-a' option on the command line interface may not be safe.
"value2"
[root@redis-node1 ~]# redis-cli -h 10.0.0.17 -a 123456 get key1
Warning: Using a password with '-a' option on the command line interface may not be safe.
"value1"

[root@redis-node1 ~]# redis-trib.rb info 10.0.0.7:6379
10.0.0.7:6379 (05d5695b...) -> 3331 keys | 5461 slots | 1 slaves.
10.0.0.17:6379 (ebe1c9d8...) -> 3340 keys | 5462 slots | 1 slaves.
10.0.0.27:6379 (ce0a9bbc...) -> 3329 keys | 5461 slots | 1 slaves.
[OK] 10000 keys in 3 masters.
0.61 keys per slot on average.

#让node2节点宕机
[root@redis-node2 ~]# systemctl stop redis

#不会立即提升,需要稍等一会儿再观察下面结果
[root@redis-node2 ~]# redis-trib.rb check 10.0.0.7:6379
>>> Performing Cluster Check (using node 10.0.0.7:6379)
M: 05d5695bdc82b2d461187ad1949def1ca402f58e 10.0.0.7:6379
   slots:0-5460 (5461 slots) master
   1 additional replica(s)
M: 6e2b44ae14bee63df6d14637dc25f7873df6c5c3 10.0.0.27:6380
   slots:5461-10922 (5462 slots) master
   0 additional replica(s)
S: 581851395649571f780989f6738a5d423f961228 10.0.0.17:6380
   slots: (0 slots) slave
   replicates 05d5695bdc82b2d461187ad1949def1ca402f58e
M: ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94 10.0.0.27:6379
   slots:10923-16383 (5461 slots) master
   1 additional replica(s)
S: e09ff1ee128352c3fa912c2ce865ffcb6b9a3e69 10.0.0.7:6380
   slots: (0 slots) slave
   replicates ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

#在新的master(即node3)上查看日志
[root@redis-node3 ~]# tail /apps/redis/log/redis-6380.log 
4846:S 25 Oct 19:24:48.209 # Currently unable to failover: Waiting the delay before I can start a new failover.
4846:S 25 Oct 19:24:48.512 * Connecting to MASTER 10.0.0.17:6379
4846:S 25 Oct 19:24:48.512 * MASTER <-> SLAVE sync started
4846:S 25 Oct 19:24:48.513 # Error condition on socket for SYNC: Connection refused
4846:S 25 Oct 19:24:48.814 # Starting a failover election for epoch 8.
4846:S 25 Oct 19:24:48.817 # Failover election won: I'm the new master.
4846:S 25 Oct 19:24:48.817 # configEpoch set to 8 after successful failover
4846:M 25 Oct 19:24:48.817 # Setting secondary replication ID to a9f0e20eb3affe694fe48802259f69b5aa550a33, valid up to offset: 137842. New replication ID is 730ab9b1b311facf78112a78fd7e97011b188242
4846:M 25 Oct 19:24:48.817 * Discarding previously cached master state.
4846:M 25 Oct 19:24:48.817 # Cluster state changed: ok

[root@redis-node3 ~]# redis-trib.rb info 10.0.0.7:6379
10.0.0.7:6379 (05d5695b...) -> 3331 keys | 5461 slots | 1 slaves.
10.0.0.27:6380 (6e2b44ae...) -> 3340 keys | 5462 slots | 0 slaves.
10.0.0.27:6379 (ce0a9bbc...) -> 3329 keys | 5461 slots | 1 slaves.
[OK] 10000 keys in 3 masters.
0.61 keys per slot on average.

将故障的master恢复后，该节点自动加入集群成为新的slave

[root@redis-node2 ~]# systemctl start redis
[root@redis-node2 ~]# redis-trib.rb check 10.0.0.7:6379
>>> Performing Cluster Check (using node 10.0.0.7:6379)
M: 05d5695bdc82b2d461187ad1949def1ca402f58e 10.0.0.7:6379
   slots:0-5460 (5461 slots) master
   1 additional replica(s)
M: 6e2b44ae14bee63df6d14637dc25f7873df6c5c3 10.0.0.27:6380
   slots:5461-10922 (5462 slots) master
   1 additional replica(s)
S: ebe1c9d8ae6bfdbc07f94d3c1b51f60f9097e592 10.0.0.17:6379
   slots: (0 slots) slave
   replicates 6e2b44ae14bee63df6d14637dc25f7873df6c5c3
S: 581851395649571f780989f6738a5d423f961228 10.0.0.17:6380
   slots: (0 slots) slave
   replicates 05d5695bdc82b2d461187ad1949def1ca402f58e
M: ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94 10.0.0.27:6379
   slots:10923-16383 (5461 slots) master
   1 additional replica(s)
S: e09ff1ee128352c3fa912c2ce865ffcb6b9a3e69 10.0.0.7:6380
   slots: (0 slots) slave
   replicates ce0a9bbcdb5e2a5e0f0d08e86b38cd63152b4c94
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

实战案例：

因公司业务发展迅猛，现有的三主三从的redis cluster架构可能无法满足现有 业务的并发写入需求，因此公司紧急采购两台服务器10.0.0.67，10.0.0.77，需 要将其动态添加到集群当中，但不能影响业务使用和数据丢失。

注意: 生产环境一般建议master节点为奇数个,比如:3,5,7,以防止脑裂现象

实战案例：

由于10.0.0.8服务器使用年限已经超过三年，已经超过厂商质保期而且硬盘出现 异常报警，经运维部架构师提交方案并同开发同事开会商议，决定将现有Redis 集群的8台主服务器中的master 10.0.0.8和对应的slave 10.0.0.38临时下线， 三台服务器的并发写入性能足够支出未来1-2年的业务需求

删除节点过程：

添加节点的时候是先添加node节点到集群，然后分配槽位，删除节点的操作与添 加节点的操作正好相反，是先将被删除的Redis node上的槽位迁移到集群中的其 他Redis node节点上，然后再将其删除，如果一个Redis node节点上的槽位没有 被完全迁移，删除该node的时候会提示有数据且无法删除。

官方提供了离线迁移数据到集群的工具,有些公司开发了离线迁移工具

• 官方工具: redis-cli –cluster import
• 第三方在线迁移工具: 模拟slave 节点实现, 比如: 唯品会 redis-migrate-tool , 豌豆荚 redis-port

实战案例：

公司将redis cluster部署完成之后，需要将之前的数据导入之Redis cluster集 群，但是由于Rediscluster使用的分片保存key的机制，因此使用传统的AOF文件 或RDB快照无法满足需求，因此需要使用集群数据导入命令完成。

注意: 导入数据需要redis cluster不能与被导入的数据有重复的key名称，否则导入不成功或中断。

redis cluster 多个节点运行一段时间后,可能会出现倾斜现象,某个节点数据偏多,内存消耗更大,或者接受用户请求访问更多

发生倾斜的原因可能如下:

• 节点和槽分配不均
• 不同槽对应键值数量差异较大
• 包含bigkey,建议少用
• 内存相关配置不一致
• 热点数据不均衡 : 一致性不高时,可以使用本地缓存和MQ

获取指定槽位中对应键key值的个数

#redis-cli cluster countkeysinslot {slot的值}

范例: 获取指定slot对应的key个数

[root@centos8 ~]#redis-cli -a centos cluster countkeysinslot 1
(integer) 0
[root@centos8 ~]#redis-cli -a centos cluster countkeysinslot 2
(integer) 0
[root@centos8 ~]#redis-cli -a centos cluster countkeysinslot 3
(integer) 1

执行自动的槽位重新平衡分布,但会影响客户端的访问,此方法慎用

#redis-cli --cluster rebalance <集群节点IP:PORT>

范例: 执行自动的槽位重新平衡分布

[root@centos8 ~]#redis-cli -a centos --cluster rebalance 10.0.0.8:6379
>>> Performing Cluster Check (using node 10.0.0.8:6379)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
*** No rebalancing needed! All nodes are within the 2.00% threshold.
:PROPERTIES:
:CUSTOM_ID: h:b5777d34-a667-43b0-ac82-e5108d82737a
:END:

获取bigkey ,建议在slave节点执行

#redis-cli --bigkeys

范例: 查找 bigkey

[root@centos8 ~]#redis-cli -a centos --bigkeys
# Scanning the entire keyspace to find biggest keys as well as
# average sizes per key type. You can use -i 0.1 to sleep 0.1 sec
# per 100 SCAN commands (not usually needed).

[00.00%] Biggest string found so far 'key8811' with 9 bytes
[26.42%] Biggest string found so far 'testkey1' with 10 bytes

-------- summary -------

Sampled 3335 keys in the keyspace!
Total key length in bytes is 22979 (avg len 6.89)

Biggest string found 'testkey1' has 10 bytes

3335 strings with 29649 bytes (100.00% of keys, avg size 8.89)
0 lists with 0 items (00.00% of keys, avg size 0.00)
0 sets with 0 members (00.00% of keys, avg size 0.00)
0 hashs with 0 fields (00.00% of keys, avg size 0.00)
0 zsets with 0 members (00.00% of keys, avg size 0.00)
0 streams with 0 entries (00.00% of keys, avg size 0.00)