Redis集群詳解

2020-10-28 21:27:30

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Redis集群詳解

Redis有三種集群模式，分別是：

* 主從模式
* Sentinel模式
* Cluster模式

三種集群模式各有特點，關于Redis介紹可以參考這里：NoSQL（二)――Redis

Redis官網：https://redis.io/ ，最新版本6.0.5

主從模式

主從模式介紹
主從模式是三種模式中最簡單的，在主從復制中，數據庫分為兩類：主數據庫(master)和從數據庫(slave)。

其中主從復制有如下特點：

* 主數據庫可以進行讀寫操作，當讀寫操作導致數據變化時會自動將數據同步給從數據庫

* 從數據庫一般都是只讀的，并且接收主數據庫同步過來的數據

* 一個master可以擁有多個slave，但是一個slave只能對應一個master

* slave掛了不影響其他slave的讀和master的讀和寫，重新啟動后會將數據從master同步過來

* master掛了以后，不影響slave的讀，但redis不再提供寫服務，master重啟后redis將重新對外提供寫服務

* master掛了以后，不會在slave節點中重新選一個master

工作機制：

當slave啟動后，主動向master發送SYNC命令。master接收到SYNC命令后在后臺保存快照（RDB持久化）和緩存保存快照這段時間的命令，然后將保存的快照文件和緩存的命令發送給slave。slave接收到快照文件和命令后加載快照文件和緩存的執行命令。

復制初始化后，master每次接收到的寫命令都會同步發送給slave，保證主從數據一致性。

安全設置：

當master節點設置密碼后，

客戶端訪問master需要密碼
啟動slave需要密碼，在配置文件中配置即可
客戶端訪問slave不需要密碼

缺點：

從上面可以看出，master節點在主從模式中唯一，若master掛掉，則redis無法對外提供寫服務。

主從模式搭建

環境準備：

master節點 192.168.30.128
slave節點 192.168.30.129
slave節點 192.168.30.130

全部下載安裝：

# cd /software# wget http://download.redis.io/releases/redis-6.0.5.tar.gz# tar zxf redis-5.0.4.tar.gz && mv redis-6.0.5/ /usr/local/redis# cd /usr/local/redis && make && make install# echo $?0

全部配置成服務：

服務文件

# vim /usr/lib/systemd/system/redis.service
[Unit]
Description=Redis persistent key-value database
After=network.target
After=network-online.target
Wants=network-online.target
[Service]
ExecStart=/usr/local/bin/redis-server /usr/local/redis/redis.conf --supervised systemd
ExecStop=/usr/libexec/redis-shutdown
Type=notify
User=redis
Group=redis
RuntimeDirectory=redis
RuntimeDirectoryMode=0755
[Install]
WantedBy=multi-user.target

shutdown腳本

# vim /usr/libexec/redis-shutdown#!/bin/bash## Wrapper to close properly redis and sentineltest x"$REDIS_DEBUG" != x && set -xREDIS_CLI=/usr/local/bin/redis-cli# Retrieve service nameSERVICE_NAME="$1"if [ -z "$SERVICE_NAME" ]; then  SERVICE_NAME=redisfi# Get the proper config file based on service nameCONFIG_FILE="/usr/local/redis/$SERVICE_NAME.conf"# Use awk to retrieve host, port from config fileHOST=`awk '/^[[:blank:]]*bind/ { print $2 }' $CONFIG_FILE | tail -n1`PORT=`awk '/^[[:blank:]]*port/ { print $2 }' $CONFIG_FILE | tail -n1`PASS=`awk '/^[[:blank:]]*requirepass/ { print $2 }' $CONFIG_FILE | tail -n1`SOCK=`awk '/^[[:blank:]]*unixsocket/s/ { print $2 }' $CONFIG_FILE | tail -n1`# Just in case, use default host, portHOST=${HOST:-127.0.0.1}if [ "$SERVICE_NAME" = redis ]; then  PORT=${PORT:-6379}else  PORT=${PORT:-26739}fi# Setup additional parameters# e.g password-protected redis instances[ -z "$PASS" ] || ADDITIONAL_PARAMS="-a $PASS"# shutdown the service properlyif [ -e "$SOCK" ] ; then    $REDIS_CLI -s $SOCK $ADDITIONAL_PARAMS shutdownelse    $REDIS_CLI -h $HOST -p $PORT $ADDITIONAL_PARAMS shutdownfi

# chmod +x /usr/libexec/redis-shutdown# useradd -s /sbin/nologin redis# chown -R redis:redis /usr/local/redis# chown -R reids:redis /data/redis# yum install -y bash-completion && source /etc/profile         #命令補全# systemctl daemon-reload# systemctl enable redis

修改配置：

192.168.30.128

# mkdir -p /data/redis# vim /usr/local/redis/redis.confbind 192.168.30.128        #監聽ip，多個ip用空格分隔daemonize yes        #允許后臺啟動logfile "/usr/local/redis/redis.log"        #日志路徑dir /data/redis         #數據庫備份文件存放目錄masterauth 123456        #slave連接master密碼，master可省略requirepass 123456       #設置master連接密碼，slave可省略appendonly yes         #在/data/redis/目錄生成appendonly.aof文件，將每一次寫操作請求都追加到appendonly.aof 文件中# echo 'vm.overcommit_memory=1' >> /etc/sysctl.conf# sysctl -p

192.168.30.129

# mkdir -p /data/redis# vim /usr/local/redis/redis.confbind 192.168.30.129daemonize yeslogfile "/usr/local/redis/redis.log"dir /data/redisreplicaof 192.168.30.128 6379masterauth 123456requirepass 123456appendonly yes# echo 'vm.overcommit_memory=1' >> /etc/sysctl.conf# sysctl -p

192.168.30.130

# mkdir -p /data/redis# vim /usr/local/redis/redis.confbind 192.168.30.130daemonize yeslogfile "/usr/local/redis/redis.log"dir /data/redisreplicaof 192.168.30.128 6379masterauth 123456requirepass 123456appendonly yes# echo 'vm.overcommit_memory=1' >> /etc/sysctl.conf# sysctl -p

全部啟動redis：

# systemctl start redis

查看集群狀態：

# redis-cli -h 192.168.30.128 -a 123456Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.192.168.30.128:6379> info replication# Replicationrole:masterconnected_slaves:2slave0:ip=192.168.30.129,port=6379,state=online,offset=168,lag=1slave1:ip=192.168.30.130,port=6379,state=online,offset=168,lag=1master_replid:fb4941e02d5032ad74c6e2383211fc58963dbe90master_replid2:0000000000000000000000000000000000000000master_repl_offset:168second_repl_offset:-1repl_backlog_active:1repl_backlog_size:1048576repl_backlog_first_byte_offset:1repl_backlog_histlen:168

# redis-cli -h 192.168.30.129 -a 123456 info replicationWarning: Using a password with '-a' or '-u' option on the command line interface may not be safe.# Replicationrole:slavemaster_host:192.168.30.128master_port:6379master_link_status:upmaster_last_io_seconds_ago:1master_sync_in_progress:0slave_repl_offset:196slave_priority:100slave_read_only:1connected_slaves:0master_replid:fb4941e02d5032ad74c6e2383211fc58963dbe90master_replid2:0000000000000000000000000000000000000000master_repl_offset:196second_repl_offset:-1repl_backlog_active:1repl_backlog_size:1048576repl_backlog_first_byte_offset:1repl_backlog_histlen:196

數據演示：

192.168.30.128:6379> keys *(empty list or set)192.168.30.128:6379> set key1 100OK192.168.30.128:6379> set key2 lzxOK192.168.30.128:6379> keys *1) "key1"2) "key2"

# redis-cli -h 192.168.30.129 -a 123456Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.192.168.30.129:6379> keys *1) "key2"2) "key1"192.168.30.129:6379> CONFIG GET dir1) "dir"2) "/data/redis"192.168.30.129:6379> CONFIG GET dbfilename1) "dbfilename"2) "dump.rdb"192.168.30.129:6379> get key1"100"192.168.30.129:6379> get key2"lzx"192.168.30.129:6379> set key3 aaa(error) READONLY You can't write against a read only replica.

# redis-cli -h 192.168.30.130 -a 123456Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.192.168.30.130:6379> keys *1) "key2"2) "key1"192.168.30.130:6379> CONFIG GET dir1) "dir"2) "/data/redis"192.168.30.130:6379> CONFIG GET dbfilename1) "dbfilename"2) "dump.rdb"192.168.30.130:6379> get key1"100"192.168.30.130:6379> get key2"lzx"192.168.30.130:6379> set key3 aaa(error) READONLY You can't write against a read only replica.

可以看到，在master節點寫入的數據，很快就同步到slave節點上，而且在slave節點上無法寫入數據。

Sentinel模式

Sentinel模式介紹
主從模式的弊端就是不具備高可用性，當master掛掉以后，Redis將不能再對外提供寫入操作，因此sentinel應運而生。

sentinel中文含義為哨兵，顧名思義，它的作用就是監控redis集群的運行狀況，特點如下：

* sentinel模式是建立在主從模式的基礎上，如果只有一個Redis節點，sentinel就沒有任何意義
* 當master掛了以后，sentinel會在slave中選擇一個做為master，并修改它們的配置文件，其他slave的配置文件也會被修改，比如slaveof屬性會指向新的master
* 當master重新啟動后，它將不再是master而是做為slave接收新的master的同步數據
* sentinel因為也是一個進程有掛掉的可能，所以sentinel也會啟動多個形成一個sentinel集群
* 多sentinel配置的時候，sentinel之間也會自動監控
* 當主從模式配置密碼時，sentinel也會同步將配置信息修改到配置文件中，不需要擔心
* 一個sentinel或sentinel集群可以管理多個主從Redis，多個sentinel也可以監控同一個redis
* sentinel最好不要和Redis部署在同一臺機器，不然Redis的服務器掛了以后，sentinel也掛了

工作機制：

* 每個sentinel以每秒鐘一次的頻率向它所知的master，slave以及其他sentinel實例發送一個 PING 命令
* 如果一個實例距離最后一次有效回復 PING 命令的時間超過 down-after-milliseconds 選項所指定的值，則這個實例會被sentinel標記為主觀下線。
* 如果一個master被標記為主觀下線，則正在監視這個master的所有sentinel要以每秒一次的頻率確認master的確進入了主觀下線狀態
* 當有足夠數量的sentinel（大于等于配置文件指定的值）在指定的時間范圍內確認master的確進入了主觀下線狀態，則master會被標記為客觀下線
* 在一般情況下，每個sentinel會以每 10 秒一次的頻率向它已知的所有master，slave發送 INFO 命令
* 當master被sentinel標記為客觀下線時，sentinel向下線的master的所有slave發送 INFO 命令的頻率會從 10 秒一次改為 1 秒一次
* 若沒有足夠數量的sentinel同意master已經下線，master的客觀下線狀態就會被移除；
若master重新向sentinel的 PING 命令返回有效回復，master的主觀下線狀態就會被移除

當使用sentinel模式的時候，客戶端就不要直接連接Redis，而是連接sentinel的ip和port，由sentinel來提供具體的可提供服務的Redis實現，這樣當master節點掛掉以后，sentinel就會感知并將新的master節點提供給使用者。

Sentinel模式搭建

環境準備：

master節點 192.168.30.128 sentinel端口：26379
slave節點 192.168.30.129 sentinel端口：26379
slave節點 192.168.30.130 sentinel端口：26379

修改配置：

前面已經下載安裝了redis，這里省略，直接修改sentinel配置文件。

192.168.30.128

# vim /usr/local/redis/sentinel.conf
daemonize yes
logfile "/usr/local/redis/sentinel.log"
dir "/usr/local/redis/sentinel"                 #sentinel工作目錄
sentinel monitor mymaster 192.168.30.128 6379 2                 #判斷master失效至少需要2個sentinel同意，建議設置為n/2+1，n為sentinel個數
sentinel auth-pass mymaster 123456
sentinel down-after-milliseconds mymaster 30000                 #判斷master主觀下線時間，默認30s

這里需要注意，sentinel auth-pass mymaster 123456需要配置在sentinel monitor mymaster 192.168.30.128 6379 2下面，否則啟動報錯：

# /usr/local/bin/redis-sentinel /usr/local/redis/sentinel.conf*** FATAL CONFIG FILE ERROR ***Reading the configuration file, at line 104>>> 'sentinel auth-pass mymaster 123456'No such master with specified name.

全部啟動sentinel：

# mkdir /usr/local/redis/sentinel && chown -R redis:redis /usr/local/redis
# /usr/local/bin/redis-sentinel /usr/local/redis/sentinel.conf

任一主機查看日志：

# tail -f /usr/local/redis/sentinel.log
21574:X 09 May 2019 15:32:04.298 # Sentinel ID is 30c417116a8edbab09708037366c4a7471beb770
21574:X 09 May 2019 15:32:04.298 # +monitor master mymaster 192.168.30.128 6379 quorum 2
21574:X 09 May 2019 15:32:04.299 * +slave slave 192.168.30.129:6379 192.168.30.129 6379 @ mymaster 192.168.30.128 6379
21574:X 09 May 2019 15:32:04.300 * +slave slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.128 6379
21574:X 09 May 2019 15:32:16.347 * +sentinel sentinel 79b8d61626afd4d059fb5a6a63393e9a1374e78f 192.168.30.129 26379 @ mymaster 192.168.30.128 6379
21574:X 09 May 2019 15:32:31.584 * +sentinel sentinel d7b429dcba792103ef0d80827dd0910bd9284d21 192.168.30.130 26379 @ mymaster 192.168.30.128 6379

Sentinel模式下的幾個事件：

? +reset-master ：主服務器已被重置。
? +slave ：一個新的從服務器已經被 Sentinel 識別并關聯。
? +failover-state-reconf-slaves ：故障轉移狀態切換到了 reconf-slaves 狀態。
? +failover-detected ：另一個 Sentinel 開始了一次故障轉移操作，或者一個從服務器轉換成了主服務器。
? +slave-reconf-sent ：領頭（leader）的 Sentinel 向實例發送了 [SLAVEOF](/commands/slaveof.html) 命令，為實例設置新的主服務器。
? +slave-reconf-inprog ：實例正在將自己設置為指定主服務器的從服務器，但相應的同步過程仍未完成。
? +slave-reconf-done ：從服務器已經成功完成對新主服務器的同步。
? -dup-sentinel ：對給定主服務器進行監視的一個或多個 Sentinel 已經因為重復出現而被移除 ―― 當 Sentinel 實例重啟的時候，就會出現這種情況。
? +sentinel ：一個監視給定主服務器的新 Sentinel 已經被識別并添加。
? +sdown ：給定的實例現在處于主觀下線狀態。
? -sdown ：給定的實例已經不再處于主觀下線狀態。
? +odown ：給定的實例現在處于客觀下線狀態。
? -odown ：給定的實例已經不再處于客觀下線狀態。
? +new-epoch ：當前的紀元（epoch）已經被更新。
? +try-failover ：一個新的故障遷移操作正在執行中，等待被大多數 Sentinel 選中（waiting to be elected by the majority）。
? +elected-leader ：贏得指定紀元的選舉，可以進行故障遷移操作了。
? +failover-state-select-slave ：故障轉移操作現在處于 select-slave 狀態 ―― Sentinel 正在尋找可以升級為主服務器的從服務器。
? no-good-slave ：Sentinel 操作未能找到適合進行升級的從服務器。Sentinel 會在一段時間之后再次嘗試尋找合適的從服務器來進行升級，又或者直接放棄執行故障轉移操作。
? selected-slave ：Sentinel 順利找到適合進行升級的從服務器。
? failover-state-send-slaveof-noone ：Sentinel 正在將指定的從服務器升級為主服務器，等待升級功能完成。
? failover-end-for-timeout ：故障轉移因為超時而中止，不過最終所有從服務器都會開始復制新的主服務器（slaves will eventually be configured to replicate with the new master anyway）。
? failover-end ：故障轉移操作順利完成。所有從服務器都開始復制新的主服務器了。
? +switch-master ：配置變更，主服務器的 IP 和地址已經改變。這是絕大多數外部用戶都關心的信息。
? +tilt ：進入 tilt 模式。
? -tilt ：退出 tilt 模式。

master宕機演示：

192.168.30.128

# systemctl stop redis
# tail -f /usr/local/redis/sentinel.log
22428:X 09 May 2019 15:51:29.287 # +sdown master mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:29.371 # +odown master mymaster 192.168.30.128 6379 #quorum 2/2
22428:X 09 May 2019 15:51:29.371 # +new-epoch 1
22428:X 09 May 2019 15:51:29.371 # +try-failover master mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:29.385 # +vote-for-leader 30c417116a8edbab09708037366c4a7471beb770 1
22428:X 09 May 2019 15:51:29.403 # d7b429dcba792103ef0d80827dd0910bd9284d21 voted for 30c417116a8edbab09708037366c4a7471beb770 1
22428:X 09 May 2019 15:51:29.408 # 79b8d61626afd4d059fb5a6a63393e9a1374e78f voted for 30c417116a8edbab09708037366c4a7471beb770 1
22428:X 09 May 2019 15:51:29.451 # +elected-leader master mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:29.451 # +failover-state-select-slave master mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:29.528 # +selected-slave slave 192.168.30.129:6379 192.168.30.129 6379 @ mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:29.528 * +failover-state-send-slaveof-noone slave 192.168.30.129:6379 192.168.30.129 6379 @ mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:29.594 * +failover-state-wait-promotion slave 192.168.30.129:6379 192.168.30.129 6379 @ mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:30.190 # +promoted-slave slave 192.168.30.129:6379 192.168.30.129 6379 @ mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:30.190 # +failover-state-reconf-slaves master mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:30.258 * +slave-reconf-sent slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:30.511 # -odown master mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:31.233 * +slave-reconf-inprog slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:31.233 * +slave-reconf-done slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:31.297 # +failover-end master mymaster 192.168.30.128 6379
22428:X 09 May 2019 15:51:31.297 # +switch-master mymaster 192.168.30.128 6379 192.168.30.129 6379
22428:X 09 May 2019 15:51:31.298 * +slave slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.129 6379
22428:X 09 May 2019 15:51:31.298 * +slave slave 192.168.30.128:6379 192.168.30.128 6379 @ mymaster 192.168.30.129 6379
22428:X 09 May 2019 15:52:31.307 # +sdown slave 192.168.30.128:6379 192.168.30.128 6379 @ mymaster 192.168.30.129 6379

從日志中可以看到，master已經從192.168.30.128轉移到192.168.30.129上

192.168.30.129上查看集群信息

# /usr/local/bin/redis-cli -h 192.168.30.129 -p 6379 -a 123456Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.192.168.30.129:6379> info replication# Replicationrole:masterconnected_slaves:1slave0:ip=192.168.30.130,port=6379,state=online,offset=291039,lag=1master_replid:757aff269236ed2707ba584a86a40716c1c76d74master_replid2:47a862fc0ff20362be29096ecdcca6d432070ee9master_repl_offset:291182second_repl_offset:248123repl_backlog_active:1repl_backlog_size:1048576repl_backlog_first_byte_offset:1repl_backlog_histlen:291182192.168.30.129:6379> set key4 linuxOK

當前集群中只有一個slave――192.168.30.130，master是192.168.30.129，且192.168.30.129具有寫權限。

192.168.30.130上查看redis的配置文件也可以看到replicaof 192.168.30.129 6379，這是sentinel在選舉master是做的修改。

重新把192.168.30.128上進程啟動

# systemctl start redis
# tail -f /usr/local/redis/sentinel.log
22428:X 09 May 2019 15:51:31.297 # +switch-master mymaster 192.168.30.128 6379 192.168.30.129 6379
22428:X 09 May 2019 15:51:31.298 * +slave slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.129 6379
22428:X 09 May 2019 15:51:31.298 * +slave slave 192.168.30.128:6379 192.168.30.128 6379 @ mymaster 192.168.30.129 6379
22428:X 09 May 2019 15:52:31.307 # +sdown slave 192.168.30.128:6379 192.168.30.128 6379 @ mymaster 192.168.30.129 6379
22428:X 09 May 2019 16:01:24.872 # -sdown slave 192.168.30.128:6379 192.168.30.128 6379 @ mymaster 192.168.30.129 6379

查看集群信息

# /usr/local/bin/redis-cli -h 192.168.30.128 -p 6379 -a 123456Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.192.168.30.128:6379> info replication# Replicationrole:slavemaster_host:192.168.30.129master_port:6379master_link_status:upmaster_last_io_seconds_ago:0master_sync_in_progress:0slave_repl_offset:514774slave_priority:100slave_read_only:1connected_slaves:0master_replid:757aff269236ed2707ba584a86a40716c1c76d74master_replid2:0000000000000000000000000000000000000000master_repl_offset:514774second_repl_offset:-1repl_backlog_active:1repl_backlog_size:1048576repl_backlog_first_byte_offset:376528repl_backlog_histlen:138247192.168.30.128:6379> get key4"linux"192.168.30.128:6379> set key5(error) ERR wrong number of arguments for 'set' command

即使192.168.30.128重新啟動redis服務，也是作為slave加入redis集群，192.168.30.129仍然是master。

Cluster模式

Cluster模式介紹
sentinel模式基本可以滿足一般生產的需求，具備高可用性。但是當數據量過大到一臺服務器存放不下的情況時，主從模式或sentinel模式就不能滿足需求了，這個時候需要對存儲的數據進行分片，將數據存儲到多個Redis實例中。cluster模式的出現就是為了解決單機Redis容量有限的問題，將Redis的數據根據一定的規則分配到多臺機器。

cluster可以說是sentinel和主從模式的結合體，通過cluster可以實現主從和master重選功能，所以如果配置兩個副本三個分片的話，就需要六個Redis實例。因為Redis的數據是根據一定規則分配到cluster的不同機器的，當數據量過大時，可以新增機器進行擴容。

使用集群，只需要將redis配置文件中的cluster-enable配置打開即可。每個集群中至少需要三個主數據庫才能正常運行，新增節點非常方便。

cluster集群特點：

* 多個redis節點網絡互聯，數據共享
* 所有的節點都是一主一從（也可以是一主多從），其中從不提供服務，僅作為備用
* 不支持同時處理多個key（如MSET/MGET），因為redis需要把key均勻分布在各個節點上，
并發量很高的情況下同時創建key-value會降低性能并導致不可預測的行為

* 支持在線增加、刪除節點
* 客戶端可以連接任何一個主節點進行讀寫

Cluster模式搭建

環境準備：

三臺機器，分別開啟兩個redis服務（端口）

192.168.30.128 端口：7001,7002
192.168.30.129 端口：7003,7004
192.168.30.130 端口：7005,7006

修改配置文件：

192.168.30.128

# mkdir /usr/local/redis/cluster
# cp /usr/local/redis/redis.conf /usr/local/redis/cluster/redis_7001.conf
# cp /usr/local/redis/redis.conf /usr/local/redis/cluster/redis_7002.conf
# chown -R redis:redis /usr/local/redis
# mkdir -p /data/redis/cluster/{redis_7001,redis_7002} && chown -R redis:redis /data/redis

# vim /usr/local/redis/cluster/redis_7001.confbind 192.168.30.128port 7001daemonize yespidfile "/var/run/redis_7001.pid"logfile "/usr/local/redis/cluster/redis_7001.log"dir "/data/redis/cluster/redis_7001"#replicaof 192.168.30.129 6379masterauth 123456requirepass 123456appendonly yescluster-enabled yescluster-config-file nodes_7001.confcluster-node-timeout 15000

# vim /usr/local/redis/cluster/redis_7002.confbind 192.168.30.128port 7002daemonize yespidfile "/var/run/redis_7002.pid"logfile "/usr/local/redis/cluster/redis_7002.log"dir "/data/redis/cluster/redis_7002"#replicaof 192.168.30.129 6379masterauth "123456"requirepass "123456"appendonly yescluster-enabled yescluster-config-file nodes_7002.confcluster-node-timeout 15000

其它兩臺機器配置與192.168.30.128一致，此處省略

啟動redis服務：

# redis-server /usr/local/redis/cluster/redis_7001.conf
# tail -f /usr/local/redis/cluster/redis_7001.log
# redis-server /usr/local/redis/cluster/redis_7002.conf
# tail -f /usr/local/redis/cluster/redis_7002.log

其它兩臺機器啟動與192.168.30.128一致，此處省略

安裝ruby并創建集群（低版本）：
如果redis版本比較低，則需要安裝ruby。任選一臺機器安裝ruby即可

# yum -y groupinstall "Development Tools"# yum install -y gdbm-devel libdb4-devel libffi-devel libyaml libyaml-devel ncurses-devel openssl-devel readline-devel tcl-devel# mkdir -p ~/rpmbuild/{BUILD,BUILDROOT,RPMS,SOURCES,SPECS,SRPMS}# wget http://cache.ruby-lang.org/pub/ruby/2.2/ruby-2.2.3.tar.gz -P ~/rpmbuild/SOURCES# wget http://raw.githubusercontent.com/tjinjin/automate-ruby-rpm/master/ruby22x.spec -P ~/rpmbuild/SPECS# rpmbuild -bb ~/rpmbuild/SPECS/ruby22x.spec# rpm -ivh ~/rpmbuild/RPMS/x86_64/ruby-2.2.3-1.el7.x86_64.rpm# gem install redis         #目的是安裝這個，用于配置集群

# cp /usr/local/redis/src/redis-trib.rb /usr/bin/
# redis-trib.rb create --replicas 1 192.168.30.128:7001 192.168.30.128:7002 192.168.30.129:7003 192.168.30.129:7004 192.168.30.130:7005 192.168.30.130:7006

創建集群：

我這里是redis6.0.5，所以不需要安裝ruby，直接創建集群即可

# redis-cli -a 123456 --cluster create 192.168.30.128:7001 192.168.30.128:7002 192.168.30.129:7003 192.168.30.129:7004 192.168.30.130:7005 192.168.30.130:7006 --cluster-replicas 1Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.>>> Performing hash slots allocation on 6 nodes...Master[0] -> Slots 0 - 5460Master[1] -> Slots 5461 - 10922Master[2] -> Slots 10923 - 16383Adding replica 192.168.30.129:7004 to 192.168.30.128:7001Adding replica 192.168.30.130:7006 to 192.168.30.129:7003Adding replica 192.168.30.128:7002 to 192.168.30.130:7005M: 80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001  slots:[0-5460] (5461 slots) masterS: b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002  replicates 6788453ee9a8d7f72b1d45a9093838efd0e501f1M: 4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003  slots:[5461-10922] (5462 slots) masterS: b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004  replicates 80c80a3f3e33872c047a8328ad579b9bea001ad8M: 6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005  slots:[10923-16383] (5461 slots) masterS: 277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006  replicates 4d74ec66e898bf09006dac86d4928f9fad81f373Can I set the above configuration? (type 'yes' to accept): yes         #輸入yes，接受上面配置>>> Nodes configuration updated>>> Assign a different config epoch to each node>>> Sending CLUSTER MEET messages to join the cluster

可以看到，

192.168.30.128:7001是master，它的slave是192.168.30.129:7004；
192.168.30.129:7003是master，它的slave是192.168.30.130:7006；
192.168.30.130:7005是master，它的slave是192.168.30.128:7002

自動生成nodes.conf文件：

# ls /data/redis/cluster/redis_7001/appendonly.aof dump.rdb nodes-7001.conf# vim /data/redis/cluster/redis_7001/nodes-7001.conf 6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557454406312 5 connected 10923-16383277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557454407000 6 connectedb4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557454408371 5 connected80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 myself,master - 0 1557454406000 1 connected 0-5460b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557454407366 4 connected4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557454407000 3 connected 5461-10922vars currentEpoch 6 lastVoteEpoch 0

集群操作

登錄集群：

# redis-cli -c -h 192.168.30.128 -p 7001 -a 123456 # -c，使用集群方式登錄

查看集群信息：

192.168.30.128:7001> CLUSTER INFO #集群狀態
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:580
cluster_stats_messages_pong_sent:551
cluster_stats_messages_sent:1131
cluster_stats_messages_ping_received:546
cluster_stats_messages_pong_received:580
cluster_stats_messages_meet_received:5
cluster_stats_messages_received:1131

列出節點信息：

192.168.30.128:7001> CLUSTER NODES         #列出節點信息6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557455176000 5 connected 10923-16383277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557455174000 6 connectedb4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557455175000 5 connected80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 myself,master - 0 1557455175000 1 connected 0-5460b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557455174989 4 connected4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557455175995 3 connected 5461-10922

這里與nodes.conf文件內容相同

寫入數據：

192.168.30.128:7001> set key111 aaa-> Redirected to slot [13680] located at 192.168.30.130:7005        #說明數據到了192.168.30.130:7005上OK192.168.30.130:7005> set key222 bbb-> Redirected to slot [2320] located at 192.168.30.128:7001         #說明數據到了192.168.30.128:7001上OK192.168.30.128:7001> set key333 ccc-> Redirected to slot [7472] located at 192.168.30.129:7003         #說明數據到了192.168.30.129:7003上OK192.168.30.129:7003> get key111-> Redirected to slot [13680] located at 192.168.30.130:7005"aaa"192.168.30.130:7005> get key333-> Redirected to slot [7472] located at 192.168.30.129:7003"ccc"192.168.30.129:7003>

可以看出redis cluster集群是去中心化的，每個節點都是平等的，連接哪個節點都可以獲取和設置數據。

當然，平等指的是master節點，因為slave節點根本不提供服務，只是作為對應master節點的一個備份。

增加節點：

192.168.30.129上增加一節點：

# cp /usr/local/redis/cluster/redis_7003.conf /usr/local/redis/cluster/redis_7007.conf# vim /usr/local/redis/cluster/redis_7007.confbind 192.168.30.129port 7007daemonize yespidfile "/var/run/redis_7007.pid"logfile "/usr/local/redis/cluster/redis_7007.log"dir "/data/redis/cluster/redis_7007"#replicaof 192.168.30.129 6379masterauth "123456"requirepass "123456"appendonly yescluster-enabled yescluster-config-file nodes_7007.confcluster-node-timeout 15000# mkdir /data/redis/cluster/redis_7007# chown -R redis:redis /usr/local/redis && chown -R redis:redis /data/redis# redis-server /usr/local/redis/cluster/redis_7007.conf

192.168.30.130上增加一節點：

# cp /usr/local/redis/cluster/redis_7005.conf /usr/local/redis/cluster/redis_7008.conf# vim /usr/local/redis/cluster/redis_7007.confbind 192.168.30.130port 7008daemonize yespidfile "/var/run/redis_7008.pid"logfile "/usr/local/redis/cluster/redis_7008.log"dir "/data/redis/cluster/redis_7008"#replicaof 192.168.30.130 6379masterauth "123456"requirepass "123456"appendonly yescluster-enabled yescluster-config-file nodes_7008.confcluster-node-timeout 15000# mkdir /data/redis/cluster/redis_7008# chown -R redis:redis /usr/local/redis && chown -R redis:redis /data/redis# redis-server /usr/local/redis/cluster/redis_7008.conf

集群中增加節點：

192.168.30.129:7003> CLUSTER MEET 192.168.30.129 7007OK192.168.30.129:7003> CLUSTER NODES4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 myself,master - 0 1557457361000 3 connected 5461-1092280c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master - 0 1557457364746 1 connected 0-5460277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557457362000 6 connectedb6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557457363000 4 connectedb4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557457362000 5 connectede51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557457362729 0 connected6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557457363739 5 connected 10923-16383

192.168.30.129:7003> CLUSTER MEET 192.168.30.130 7008OK192.168.30.129:7003> CLUSTER NODES4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 myself,master - 0 1557457489000 3 connected 5461-1092280c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master - 0 1557457489000 1 connected 0-5460277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557457489000 6 connectedb6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557457488000 4 connectedb4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557457489472 5 connected1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 master - 0 1557457489259 0 connectede51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557457489000 0 connected6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557457490475 5 connected 10923-16383

可以看到，新增的節點都是以master身份加入集群的

更換節點身份：

將新增的192.168.30.130:7008節點身份改為192.168.30.129:7007的slave

# redis-cli -c -h 192.168.30.130 -p 7008 -a 123456 cluster replicate e51ab166bc0f33026887bcf8eba0dff3d5b0bf14

cluster replicate后面跟node_id，更改對應節點身份。也可以登入集群更改

# redis-cli -c -h 192.168.30.130 -p 7008 -a 123456192.168.30.130:7008> CLUSTER REPLICATE e51ab166bc0f33026887bcf8eba0dff3d5b0bf14OK192.168.30.130:7008> CLUSTER NODES277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557458316881 3 connected80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master - 0 1557458314864 1 connected 0-54604d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557458316000 3 connected 5461-109226788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557458315872 5 connected 10923-16383b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557458317890 5 connected1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557458315000 7 connectedb6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557458315000 1 connectede51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557458314000 0 connected

查看相應的nodes.conf文件，可以發現有更改，它記錄當前集群的節點信息

# cat /data/redis/cluster/redis_7001/nodes-7001.conf
1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557458236169 7 connected
6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557458235000 5 connected 10923-16383
277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557458234103 6 connected
b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557458235129 5 connected
80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 myself,master - 0 1557458234000 1 connected 0-5460
b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557458236000 4 connected
e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557458236000 0 connected
4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557458233089 3 connected 5461-10922
vars currentEpoch 7 lastVoteEpoch 0

刪除節點：

192.168.30.130:7008> CLUSTER FORGET 1a1c7f02fce87530bd5abdfc98df1cffce4f1767
(error) ERR I tried hard but I can't forget myself... #無法刪除登錄節點
192.168.30.130:7008> CLUSTER FORGET e51ab166bc0f33026887bcf8eba0dff3d5b0bf14
(error) ERR Can't forget my master! #不能刪除自己的master節點
192.168.30.130:7008> CLUSTER FORGET 6788453ee9a8d7f72b1d45a9093838efd0e501f1
OK #可以刪除其它的master節點
192.168.30.130:7008> CLUSTER NODES
277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557458887328 3 connected
80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master - 0 1557458887000 1 connected 0-5460
4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557458886000 3 connected 5461-10922
b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave - 0 1557458888351 5 connected
1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557458885000 7 connected
b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557458883289 1 connected
e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557458885310 0 connected
192.168.30.130:7008> CLUSTER FORGET b4d3eb411a7355d4767c6c23b4df69fa183ef8bc
OK #可以刪除其它的slave節點
192.168.30.130:7008> CLUSTER NODES
277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557459031397 3 connected
80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master - 0 1557459032407 1 connected 0-5460
4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557459035434 3 connected 5461-10922
6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557459034000 5 connected 10923-16383
1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557459032000 7 connected
b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557459034000 1 connected
e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557459034427 0 connected

保存配置：

192.168.30.130:7008> CLUSTER SAVECONFIG #將節點配置信息保存到硬盤
OK

# cat /data/redis/cluster/redis_7001/nodes-7001.conf
1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557458236169 7 connected
6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557458235000 5 connected 10923-16383
277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557458234103 6 connected
b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557458235129 5 connected
80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 myself,master - 0 1557458234000 1 connected 0-5460
b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557458236000 4 connected
e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557458236000 0 connected
4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557458233089 3 connected 5461-10922
vars currentEpoch 7 lastVoteEpoch 0
# redis-cli -c -h 192.168.30.130 -p 7008 -a 123456
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
192.168.30.130:7008> CLUSTER NODES
277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557459500741 3 connected
80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master - 0 1557459500000 1 connected 0-5460
4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557459501000 3 connected 5461-10922
6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557459500000 5 connected 10923-16383
b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557459499737 5 connected
1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557459499000 7 connected
b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557459501750 1 connected
e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557459498000 0 connected

可以看到，之前刪除的節點又恢復了，這是因為對應的配置文件沒有刪除，執行CLUSTER SAVECONFIG恢復。

模擬master節點掛掉：

192.168.30.128

# netstat -lntp |grep 7001tcp    0   0 192.168.30.128:17001  0.0.0.0:*        LISTEN   6701/redis-server 1 tcp    0   0 192.168.30.128:7001   0.0.0.0:*        LISTEN   6701/redis-server 1 # kill 6701

192.168.30.130:7008> CLUSTER NODES
277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557461178000 3 connected
80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master,fail - 1557460950483 1557460947145 1 disconnected
4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557461174922 3 connected 5461-10922
6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557461181003 5 connected 10923-16383
b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557461179993 5 connected
1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557461176000 7 connected
b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 master - 0 1557461178981 8 connected 0-5460
e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557461179000 0 connected

對應7001的一行可以看到，master fail，狀態為disconnected；而對應7004的一行，slave已經變成master。

重新啟動7001節點：

# redis-server /usr/local/redis/cluster/redis_7001.conf192.168.30.130:7008> CLUSTER NODES277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557461307000 3 connected80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 slave b6331cbc986794237c83ed2d5c30777c1551546e 0 1557461305441 8 connected4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557461307962 3 connected 5461-109226788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557461304935 5 connected 10923-16383b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557461306000 5 connected1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557461305000 7 connectedb6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 master - 0 1557461308972 8 connected 0-5460e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557461307000 0 connected

可以看到，7001節點啟動后為slave節點，并且是7004的slave節點。即master節點如果掛掉，它的slave節點變為新master節點繼續對外提供服務，而原來的master節點如果重啟，則變為新master節點的slave節點。

另外，如果這里是拿7007節點做測試的話，會發現7008節點并不會切換，這是因為7007節點上根本沒數據。集群數據被分為三份，采用哈希槽 (hash slot)的方式來分配16384個slot的話，它們三個節點分別承擔的slot 區間是：