哨兵集群介绍
Redis的哨兵(sentinel) 常用于管理多个 Redis 服务器，它主要会执行以下三个任务:
监控(Monitoring)：哨兵(sentinel) 会不断地检查你的Master和Slave是否运作正常。
提醒(Notification)：当被监控的某个 Redis出现问题时, 哨兵(sentinel) 可以通过 API 向管理员或者其他应用程序发送通知。
自动故障迁移(Automatic failover)：当一个Master不能正常工作时，哨兵(sentinel) 会开始一次自动故障迁移操作，它会将 Master 故障后的其中一个 Slave 升级为新的 Master，并让 Master 故障后的其他 Slave 改为复制新的Master；当客户端试图连接故障的 Master 时，集群也会向客户端返回新Master的地址，使得集群可以使用新的 Master 代替故障的 Master。
哨兵(sentinel) 是一个分布式系统，你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(gossipprotocols)来接收关于 Master 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) 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时间(可配置)内未回应，则暂时认为对方已挂(所谓的”主观认为宕机” Subjective Down,简称sdown)。
若“哨兵群”中的多数 sentinel ，报告某一 Master 没响应,系统才认为该 Master "彻底死亡"(即：客观上的真正down机,Objective Down,简称odown)，通过一定的vote算法,从剩下的slave节点中,选一台提升为master,然后自动修改相关配置。
虽然哨兵(sentinel) 释出为一个单独的可执行文件 redis-sentinel ,但实际上它只是一个运行在特殊模式下的 Redis 服务器，你可以在启动一个普通 Redis 服务器时通过给定 --sentinel 选项来启动哨兵(sentinel)。
服务器规划
Redis安装
下载官方安装包：https://redis.io/download
1、Redis支持包安装
由于 Redis 是由 C 语言编写，所系统需要安装 gcc
[root@rocketmq-nameserver1 ~]# yum install -y gcc automake autoconf libtool make
2、解压下载的 Redis 安装包，并进入目录，进行编译，分别在3台服务器上操作。
[root@rocketmq-nameserver1 redis-5.0.4]# make install
此过程大概需要2分钟左右，耐心等待。。。。。。
说明：如果在编译过程中出现 该错误，则需要在编译的时候使用此命令 make MALLOC=libc install 可解决。
3、复制 Redis 命令文件到 /usr/bin 目录
[root@rocketmq-nameserver1 redis-5.0.4]# cd src/
[root@rocketmq-nameserver1 src]# cp redis-cli redis-sentinel redis-server /usr/bin
redis配置
过滤 Redis 配置文件 redis.conf
[root@rocketmq-nameserver1 redis-5.0.4]# grep -Ev "^#|^$" redis.conf
bind 192.168.2.177
protected-mode yes
port 6379
tcp-backlog 511
timeout 0
tcp-keepalive 300
daemonize yes
supervised no
pidfile /wdata/redis/data/redis.pid
loglevel notice
logfile "/wdata/redis/logs/redis.log"
databases 16
always-show-logo yes
save 900 1
save 300 10
save 60 10000
stop-writes-on-bgsave-error yes
rdbcompression yes
rdbchecksum yes
dbfilename dump.rdb
dir /wdata/redis
replicaof 192.168.2.177 6379
replica-serve-stale-data yes
replica-read-only yes
repl-diskless-sync no
repl-diskless-sync-delay 5
repl-disable-tcp-nodelay no
replica-priority 100
lazyfree-lazy-eviction no
lazyfree-lazy-expire no
lazyfree-lazy-server-del no
replica-lazy-flush no
appendonly no
appendfilename "appendonly.aof"
appendfsync everysec
no-appendfsync-on-rewrite no
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb
aof-load-truncated yes
aof-use-rdb-preamble yes
lua-time-limit 5000
slowlog-log-slower-than 10000
slowlog-max-len 128
latency-monitor-threshold 0
notify-keyspace-events ""
hash-max-ziplist-entries 512
hash-max-ziplist-value 64
list-max-ziplist-size -2
list-compress-depth 0
set-max-intset-entries 512
zset-max-ziplist-entries 128
zset-max-ziplist-value 64
hll-sparse-max-bytes 3000
stream-node-max-bytes 4096
stream-node-max-entries 100
activerehashing yes
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit replica 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60
hz 10
dynamic-hz yes
aof-rewrite-incremental-fsync yes
rdb-save-incremental-fsync yes
我们对 Redis 配置文件的修改，大概只需要修改上面标红的部分，其他选项可根据自己的需要修改。其中下面两项为
daemonize yes：设置 Redis 启动时在后台运行
replicaof 192.168.2.177 6379：设置集群 Master 服务器地址和端口，注意，在 192.168.2.177 主Redis 服务器上将该项注释
将修改好的配置文件复制到其他两台服务器
for i in 178 180; do scp redis.conf root@192.168.2.$i:/wdata/redis/config; done
哨兵配置
过滤 sentinel 配置文件 sentinel.conf
[root@rocketmq-nameserver1 redis-5.0.4]# grep -Ev "^#|^$" sentinel.conf
bind 192.168.2.177
port 26379
daemonize yes
pidfile /wdata/redis-sentinel.pid
logfile "/wdata/redis/logs/sentinel.log"
dir /wdata/redis
sentinel monitor mymaster 192.168.2.177 6379 2
sentinel down-after-milliseconds mymaster 30000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 180000
sentinel deny-scripts-reconfig yes
一般，我们只需要修改上面标红的部分，其他选项根据实际需要进行修改，其中下面意向的含义为
sentinel monitor mymaster 192.168.2.177 6379 2：设置哨兵监控的主服务器为 192.168.2.177，端口为6379，2 表示如果同时有 2 个哨兵都认为该主服务器不可访问时，则进行故障转移。
将修改好的 sentinel 配置文件分发到其他两台服务器。
for i in 178 180; do scp sentinel.conf root@192.168.2.$i:/wdata/redis/config; done
启动Redis
在三台服务器上分别执行
[root@rocketmq-nameserver1 ~]# service redis start
查看 Redis 是否启动成功
[root@rocketmq-nameserver1 ~]# ps -ef | grep redis
或者
[root@rocketmq-nameserver1 ~]# service redis status
启动哨兵
在三台服务器上分别执行
[root@rocketmq-nameserver1 ~]# service sentinel start
查看哨兵启动是否成功
[root@rocketmq-nameserver1 ~]# ps -ef | grep sentinel
或者
[root@rocketmq-nameserver1 ~]# service sentinel status
查看哨兵集群状态
我们的 Redis 服务和哨兵(sentinel)服务均已成功启动，接下来我们需要验证一下集群是否正常。
[root@rocketmq-nameserver1 ~]# redis-cli -h 192.168.2.177 -p 26379
192.168.2.177:26379> SENTINEL sentinels mymaster
1) 1) "name"
2) "648ced6a4a5126ffe053c7190a7787ce8507122d"
3) "ip"
4) "192.168.2.178"
5) "port"
6) "26379"
7) "runid"
8) "648ced6a4a5126ffe053c7190a7787ce8507122d"
9) "flags"
10) "sentinel"
11) "link-pending-commands"
12) "0"
13) "link-refcount"
14) "1"
15) "last-ping-sent"
16) "0"
17) "last-ok-ping-reply"
18) "203"
19) "last-ping-reply"
20) "203"
21) "down-after-milliseconds"
22) "30000"
23) "last-hello-message"
24) "425"
25) "voted-leader"
26) "?"
27) "voted-leader-epoch"
28) "0"
2) 1) "name"
2) "25133c581dc5a5dcc41ed40d720bf417b70d6449"
3) "ip"
4) "192.168.2.180"
5) "port"
6) "26379"
7) "runid"
8) "25133c581dc5a5dcc41ed40d720bf417b70d6449"
9) "flags"
10) "sentinel"
11) "link-pending-commands"
12) "0"
13) "link-refcount"
14) "1"
15) "last-ping-sent"
16) "0"
17) "last-ok-ping-reply"
18) "203"
19) "last-ping-reply"
20) "203"
21) "down-after-milliseconds"
22) "30000"
23) "last-hello-message"
24) "870"
25) "voted-leader"
26) "?"
27) "voted-leader-epoch"
28) "0"
由输出可见，其他两个哨兵运行正常
192.168.2.177:26379> SENTINEL masters
1) 1) "name"
2) "mymaster"
3) "ip"
4) "192.168.2.177"
5) "port"
6) "6379"
7) "runid"
8) "f2c92c055ec129186fec93d0b394a99ad120fd1d"
9) "flags"
10) "master"
11) "link-pending-commands"
12) "0"
13) "link-refcount"
14) "1"
15) "last-ping-sent"
16) "0"
17) "last-ok-ping-reply"
18) "800"
19) "last-ping-reply"
20) "800"
21) "down-after-milliseconds"
22) "30000"
23) "info-refresh"
24) "10034"
25) "role-reported"
26) "master"
27) "role-reported-time"
28) "120535"
29) "config-epoch"
30) "0"
31) "num-slaves"
32) "2"
33) "num-other-sentinels"
34) "2"
35) "quorum"
36) "2"
37) "failover-timeout"
38) "180000"
39) "parallel-syncs"
40) "1"
由上输出可见，主 Redis 正常
192.168.2.177:26379> SENTINEL slaves mymaster
1) 1) "name"
2) "192.168.2.180:6379"
3) "ip"
4) "192.168.2.180"
5) "port"
6) "6379"
7) "runid"
8) "2675617f208ace5c13161e133819be75f7079946"
9) "flags"
10) "slave"
11) "link-pending-commands"
12) "0"
13) "link-refcount"
14) "1"
15) "last-ping-sent"
16) "0"
17) "last-ok-ping-reply"
18) "448"
19) "last-ping-reply"
20) "448"
21) "down-after-milliseconds"
22) "30000"
23) "info-refresh"
24) "4606"
25) "role-reported"
26) "slave"
27) "role-reported-time"
28) "235584"
29) "master-link-down-time"
30) "0"
31) "master-link-status"
32) "ok"
33) "master-host"
34) "192.168.2.177"
35) "master-port"
36) "6379"
37) "slave-priority"
38) "100"
39) "slave-repl-offset"
40) "47120"
2) 1) "name"
2) "192.168.2.178:6379"
3) "ip"
4) "192.168.2.178"
5) "port"
6) "6379"
7) "runid"
8) "803d8178c44a4380243523248dca0838c7964299"
9) "flags"
10) "slave"
11) "link-pending-commands"
12) "0"
13) "link-refcount"
14) "1"
15) "last-ping-sent"
16) "0"
17) "last-ok-ping-reply"
18) "448"
19) "last-ping-reply"
20) "448"
21) "down-after-milliseconds"
22) "30000"
23) "info-refresh"
24) "4606"
25) "role-reported"
26) "slave"
27) "role-reported-time"
28) "235627"
29) "master-link-down-time"
30) "0"
31) "master-link-status"
32) "ok"
33) "master-host"
34) "192.168.2.177"
35) "master-port"
36) "6379"
37) "slave-priority"
38) "100"
39) "slave-repl-offset"
40) "47120"
由上输出可见 Redis 从服务正常。
哨兵集群常用命令
SENTINEL masters #列出所有被监视的master，以及当前master状态
SENTINEL master <master name> #列出指定的master
SENTINEL slaves <master name> #列出给定master的所有slave以及slave状态
SENTINEL sentinels <master name> #列出监控指定的master的所有sentinel
SENTINEL get-master-addr-by-name <master name> #返回给定master名字的服务器的IP地址和端口号
SENTINEL reset <pattern> #重置所有匹配pattern表达式的master状态
SENTINEL failover <master name> #当msater失效时， 在不询问其他 Sentinel 意见的情况下， 强制开始一次自动故障迁移，但是它会给其他sentinel发送一个最新的配置，其他sentinel会根据这个配置进行更新
SENTINEL ckquorum <master name> #检查当前sentinel的配置能否达到故障切换master所需的数量，此命令可用于检测sentinel部署是否正常,正常返回ok
SENTINEL flushconfig #强制sentinel将运行时配置写入磁盘，包括当前sentinel状态
redis启动脚本
#!/bin/sh
#chkconfig: 2345 55 25
#
# Simple Redis init.d script conceived to work on Linux systems
# as it does use of the /proc filesystem.
### BEGIN INIT INFO
# Provides: redis_6379
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Redis data structure server
# Description: Redis data structure server. See https://redis.io
### END INIT INFO
source /etc/init.d/functions
REDISPORT=6379
EXEC=/usr/bin/redis-server
CLIEXEC=/usr/bin/redis-cli
PIDFILE=/wdata/redis/data/redis.pid
CONF="/wdata/redis/config/redis.conf"
AUTH=""
BIND_IP='192.168.2.177'
start(){
if [ -f $PIDFILE ]
then
echo "$PIDFILE exists, process is already running or crashed"
else
echo "Starting Redis server..."
$EXEC $CONF
fi
if [ "$?"="0" ]
then
echo "Redis is running..."
else
echo "Redis not running !"
fi
}
stop(){
if [ ! -f $PIDFILE ]
then
echo "$PIDFILE does not exist, process is not running"
else
PID=$(cat $PIDFILE)
echo "Stopping ..."
#$CLIEXEC -h $BIND_IP -a $AUTH -p $REDISPORT shutdown
$CLIEXEC -h $BIND_IP -p $REDISPORT shutdown
while [ -x /proc/${PID} ]
do
echo "Waiting for Redis to shutdown ..."
sleep 1
done
echo "Redis stopped."
fi
}
status(){
ps -ef | grep redis-server | grep -v grep >/dev/null 2>&1
if [ $? -eq 0 ];then
echo "redis server is running."
else
echo "redis server is stopped."
fi
}
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
stop
start
;;
status)
status
;;
*)
echo "Please use start or stop as first argument"
;;
esacsentinel启动脚本
#!/bin/sh
#chkconfig: 2345 55 25
#
# Simple Sentinel init.d script conceived to work on Linux systems
# as it does use of the /proc filesystem.
### BEGIN INIT INFO
# Provides: redis_6379
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Sentinel data structure server
# Description: Sentinel data structure server. See https://redis.io
### END INIT INFO
source /etc/init.d/functions
REDISPORT=26379
EXEC=/usr/bin/redis-sentinel
CLIEXEC=/usr/bin/redis-cli
PIDFILE=/wdata/redis/data/redis-sentinel.pid
CONF="/wdata/redis/config/sentinel.conf"
AUTH=""
BIND_IP='192.168.2.177'
start(){
if [ -f $PIDFILE ]
then
echo "$PIDFILE exists, process is already running or crashed"
else
echo "Starting Sentinel server..."
$EXEC $CONF
fi
if [ "$?"="0" ]
then
echo "Sentinel is running..."
else
echo "Sentinel not running !"
fi
}
stop(){
if [ ! -f $PIDFILE ]
then
echo "$PIDFILE does not exist, process is not running"
else
PID=$(cat $PIDFILE)
echo "Stopping ..."
#$CLIEXEC -h $BIND_IP -a $AUTH -p $REDISPORT shutdown
$CLIEXEC -h $BIND_IP -p $REDISPORT shutdown
while [ -x /proc/${PID} ]
do
echo "Waiting for Sentinel to shutdown ..."
sleep 1
done
echo "Sentinel stopped."
fi
}
status(){
ps -ef | grep redis-sentinel | grep -v grep >/dev/null 2>&1
if [ $? -eq 0 ];then
echo "Sentinel server is running."
else
echo "Sentinel server is stopped."
fi
}
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
stop
start
;;
status)
status
;;
*)
echo "Please use start or stop as first argument"
;;
esac