哨兵集羣介紹
Redis的哨兵(sentinel) 常用於管理多個 Redis 服務器，它主要會執行以下三個任務:
監控(Monitoring)：哨兵(sentinel) 會不斷地檢查你的Master和Slave是否運作正常。
提醒(Notification)：當被監控的某個 Redis出現問題時, 哨兵(sentinel) 可以通過 API 向管理員或者其他應用程序發送通知。
自動故障遷移(Automatic failover)：當一個Master不能正常工作時，哨兵(sentinel) 會開始一次自動故障遷移操作，它會將 Master 故障後的其中一個 Slave 升級爲新的 Master，並讓 Master 故障後的其他 Slave 改爲複製新的Master；當客戶端試圖連接故障的 Master 時，集羣也會向客戶端返回新Master的地址，使得集羣可以使用新的 Master 代替故障的 Master。
哨兵(sentinel) 是一個分佈式系統，你可以在一個架構中運行多個哨兵(sentinel) 進程，這些進程使用流言協議(gossipprotocols)來接收關於 Master 是否下線的信息，並使用投票協議(agreement protocols)來決定是否執行自動故障遷移，以及選擇哪個 Slave 作爲新的 Master。
每個哨兵(sentinel) 會向其它哨兵(sentinel)、master、slave定時發送消息，以確認對方是否“活”着，如果發現對方在指定時間(可配置)內未迴應，則暫時認爲對方已掛(所謂的”主觀認爲宕機” Subjective Down,簡稱sdown)。
若“哨兵羣”中的多數 sentinel ，報告某一 Master 沒響應,系統才認爲該 Master "徹底死亡"(即：客觀上的真正down機,Objective Down,簡稱odown)，通過一定的vote算法,從剩下的slave節點中,選一臺提升爲master,然後自動修改相關配置。
雖然哨兵(sentinel) 釋出爲一個單獨的可執行文件 redis-sentinel ,但實際上它只是一個運行在特殊模式下的 Redis 服務器，你可以在啓動一個普通 Redis 服務器時通過給定 --sentinel 選項來啓動哨兵(sentinel)。
服務器規劃
Redis安裝
下載官方安裝包：https://redis.io/download
1、Redis支持包安裝
由於 Redis 是由 C 語言編寫，所繫統需要安裝 gcc
[root@rocketmq-nameserver1 ~]# yum install -y gcc automake autoconf libtool make
2、解壓下載的 Redis 安裝包，並進入目錄，進行編譯，分別在3臺服務器上操作。
[root@rocketmq-nameserver1 redis-5.0.4]# make install
此過程大概需要2分鐘左右，耐心等待。。。。。。
說明：如果在編譯過程中出現 該錯誤，則需要在編譯的時候使用此命令 make MALLOC=libc install 可解決。
3、複製 Redis 命令文件到 /usr/bin 目錄
[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
過濾 Redis 配置文件 redis.conf
[root@rocketmq-nameserver1 redis-5.0.4]# grep -Ev "^#|^$" redis.conf
bind 192.168.2.177
protected-mode yes
port 6379
tcp-backlog 511
timeout 0
tcp-keepalive 300
daemonize yes
supervised no
pidfile /wdata/redis/data/redis.pid
loglevel notice
logfile "/wdata/redis/logs/redis.log"
databases 16
always-show-logo yes
save 900 1
save 300 10
save 60 10000
stop-writes-on-bgsave-error yes
rdbcompression yes
rdbchecksum yes
dbfilename dump.rdb
dir /wdata/redis
replicaof 192.168.2.177 6379
replica-serve-stale-data yes
replica-read-only yes
repl-diskless-sync no
repl-diskless-sync-delay 5
repl-disable-tcp-nodelay no
replica-priority 100
lazyfree-lazy-eviction no
lazyfree-lazy-expire no
lazyfree-lazy-server-del no
replica-lazy-flush no
appendonly no
appendfilename "appendonly.aof"
appendfsync everysec
no-appendfsync-on-rewrite no
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb
aof-load-truncated yes
aof-use-rdb-preamble yes
lua-time-limit 5000
slowlog-log-slower-than 10000
slowlog-max-len 128
latency-monitor-threshold 0
notify-keyspace-events ""
hash-max-ziplist-entries 512
hash-max-ziplist-value 64
list-max-ziplist-size -2
list-compress-depth 0
set-max-intset-entries 512
zset-max-ziplist-entries 128
zset-max-ziplist-value 64
hll-sparse-max-bytes 3000
stream-node-max-bytes 4096
stream-node-max-entries 100
activerehashing yes
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit replica 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60
hz 10
dynamic-hz yes
aof-rewrite-incremental-fsync yes
rdb-save-incremental-fsync yes
我們對 Redis 配置文件的修改，大概只需要修改上面標紅的部分，其他選項可根據自己的需要修改。其中下面兩項爲
daemonize yes：設置 Redis 啓動時在後臺運行
replicaof 192.168.2.177 6379：設置集羣 Master 服務器地址和端口，注意，在 192.168.2.177 主Redis 服務器上將該項註釋
將修改好的配置文件複製到其他兩臺服務器
for i in 178 180; do scp redis.conf [email protected].$i:/wdata/redis/config; done
哨兵配置
過濾 sentinel 配置文件 sentinel.conf
[root@rocketmq-nameserver1 redis-5.0.4]# grep -Ev "^#|^$" sentinel.conf
bind 192.168.2.177
port 26379
daemonize yes
pidfile /wdata/redis-sentinel.pid
logfile "/wdata/redis/logs/sentinel.log"
dir /wdata/redis
sentinel monitor mymaster 192.168.2.177 6379 2
sentinel down-after-milliseconds mymaster 30000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 180000
sentinel deny-scripts-reconfig yes
一般，我們只需要修改上面標紅的部分，其他選項根據實際需要進行修改，其中下面意向的含義爲
sentinel monitor mymaster 192.168.2.177 6379 2：設置哨兵監控的主服務器爲 192.168.2.177，端口爲6379，2 表示如果同時有 2 個哨兵都認爲該主服務器不可訪問時，則進行故障轉移。
將修改好的 sentinel 配置文件分發到其他兩臺服務器。
for i in 178 180; do scp sentinel.conf [email protected].$i:/wdata/redis/config; done
啓動Redis
在三臺服務器上分別執行
[root@rocketmq-nameserver1 ~]# service redis start
查看 Redis 是否啓動成功
[root@rocketmq-nameserver1 ~]# ps -ef | grep redis
或者
[root@rocketmq-nameserver1 ~]# service redis status
啓動哨兵
在三臺服務器上分別執行
[root@rocketmq-nameserver1 ~]# service sentinel start
查看哨兵啓動是否成功
[root@rocketmq-nameserver1 ~]# ps -ef | grep sentinel
或者
[root@rocketmq-nameserver1 ~]# service sentinel status
查看哨兵集羣狀態
我們的 Redis 服務和哨兵(sentinel)服務均已成功啓動，接下來我們需要驗證一下集羣是否正常。
[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"
由輸出可見，其他兩個哨兵運行正常
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"
由上輸出可見，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"
由上輸出可見 Redis 從服務正常。
哨兵集羣常用命令
SENTINEL masters #列出所有被監視的master，以及當前master狀態 SENTINEL master <master name> #列出指定的master SENTINEL slaves <master name> #列出給定master的所有slave以及slave狀態 SENTINEL sentinels <master name> #列出監控指定的master的所有sentinel SENTINEL get-master-addr-by-name <master name> #返回給定master名字的服務器的IP地址和端口號 SENTINEL reset <pattern> #重置所有匹配pattern表達式的master狀態 SENTINEL failover <master name> #當msater失效時， 在不詢問其他 Sentinel 意見的情況下， 強制開始一次自動故障遷移，但是它會給其他sentinel發送一個最新的配置，其他sentinel會根據這個配置進行更新 SENTINEL ckquorum <master name> #檢查當前sentinel的配置能否達到故障切換master所需的數量，此命令可用於檢測sentinel部署是否正常,正常返回ok SENTINEL flushconfig #強制sentinel將運行時配置寫入磁盤，包括當前sentinel狀態
redis啓動腳本
#!/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啓動腳本
#!/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