環境
CentOS7.2
redis3.2.8
10.1.0.160637926379主10.1.0.161637926379從110.1.0.71637926379從22. redis程序安裝
以下是單redis安裝腳本，可適用于單redis使用。 cat install_redis.sh
#!/usr/bin/env bash
# It\\\'s Used to be install redis.
# Created on 2016/10/19 11:18.
# @author: Chinge_Yang.
# Version: 1.0
function install_redis () {
#################################################################################################
sourcepackage_dir=/tmp
redis_install_dir=/usr/local/redis
cd ${sourcepackage_dir}
if [ ! -f redis-stable.tar.gz ]; then
wget http://download.redis.io/releases/redis-stable.tar.gz
fi
cd ${makework_dir}
tar -zxvf ${sourcepackage_dir}/redis-stable.tar.gz
cd redis-stable
make PREFIX=/usr/local/redis install
return_echo make
mkdir -p /usr/local/redis/{etc,var}
rsync -avz redis.conf /usr/local/redis/etc/
sed -i \\\'s@pidfile.*@pidfile /var/run/redis-server.pid@\\\' $redis_install_dir/etc/redis.conf
sed -i s@logfile.*@logfile $redis_install_dir/var/redis.log@ $redis_install_dir/etc/redis.conf
sed -i s@^dir.*@dir $redis_install_dir/var@ $redis_install_dir/etc/redis.conf
sed -i \\\'s/daemonize no/daemonize yes/g\\\' /usr/local/redis/etc/redis.conf
sed -i \\\'s/^# bind 127.0.0.1/bind 127.0.0.1/g\\\' /usr/local/redis/etc/redis.conf
rsync -avz ${sourcepackage_dir}/init.d/redis-server /etc/init.d/
/etc/init.d/redis-server start
chkconfig --add redis-server
chkconfig redis-server on
#################################################################################################
}
install_redis
redis啟停腳本示例： cat redis-server
#!/bin/bash
#
# redis - this script starts and stops the redis-server daemon
#
# chkconfig: - 85 15
# description: Redis is a persistent key-value database
# processname: redis-server
# config: /usr/local/redis/etc/redis.conf
# config: /etc/sysconfig/redis
# pidfile: /usr/local/redis/var/redis-server.pid
# Source function library.
. /etc/rc.d/init.d/functions
# Source networking configuration.
. /etc/sysconfig/network
# Check that networking is up.
[ $NETWORKING = no ] && exit 0
redis=/usr/local/redis/bin/redis-server
prog=$(basename $redis)
REDIS_CONF_FILE=/usr/local/redis/etc/redis.conf
[ -f /etc/sysconfig/redis ] && . /etc/sysconfig/redis
lockfile=/var/lock/subsys/redis-server
start() {
[ -x $redis ] || exit 5
[ -f $REDIS_CONF_FILE ] || exit 6
echo -n $Starting $prog:
daemon $redis $REDIS_CONF_FILE
retval=$?
echo
[ $retval -eq 0 ] && touch $lockfile
return $retval
}
stop() {
echo -n $Stopping $prog:
killproc $prog
retval=$?
echo
[ $retval -eq 0 ] && rm -f $lockfile
return $retval
}
restart() {
stop
start
}
reload() {
echo -n $Reloading $prog:
killproc $redis -HUP
RETVAL=$?
echo
}
force_reload() {
restart
}
rh_status() {
status $prog
}
rh_status_q() {
rh_status >/dev/null 2>&1
}
case $1 in
start)
rh_status_q && exit 0
$1
;;
stop)
rh_status_q || exit 0
$1
;;
restart)
$1
;;
reload)
rh_status_q || exit 7
$1
;;
force-reload)
force_reload
;;
status)
rh_status
;;
condrestart|try-restart)
rh_status_q || exit 0
;;
*)
echo $Usage: $0 {start|stop|status|restart|condrestart|try-restart|reload|force-reload}
exit 2
esac
redis-sentinel啟停腳本示例：
#!/bin/bash
#
# redis-sentinel - this script starts and stops the redis-server sentinel daemon
#
# chkconfig: - 85 15
# description: Redis sentinel
# processname: redis-server
# config: /usr/local/redis/etc/sentinel.conf
# config: /etc/sysconfig/redis
# pidfile: /usr/local/redis/var/redis-sentinel.pid
# Source function library.
. /etc/rc.d/init.d/functions
# Source networking configuration.
. /etc/sysconfig/network
# Check that networking is up.
[ $NETWORKING = no ] && exit 0
redis=/usr/local/redis/bin/redis-sentinel
prog=$(basename $redis)
REDIS_CONF_FILE=/usr/local/redis/etc/sentinel.conf
[ -f /etc/sysconfig/redis ] && . /etc/sysconfig/redis
lockfile=/var/lock/subsys/redis-sentinel
start() {
[ -x $redis ] || exit 5
[ -f $REDIS_CONF_FILE ] || exit 6
echo -n $Starting $prog:
daemon $redis $REDIS_CONF_FILE --sentinel
retval=$?
echo
[ $retval -eq 0 ] && touch $lockfile
return $retval
}
stop() {
echo -n $Stopping $prog:
killproc $prog
retval=$?
echo
[ $retval -eq 0 ] && rm -f $lockfile
return $retval
}
restart() {
stop
start
}
reload() {
echo -n $Reloading $prog:
killproc $redis -HUP
RETVAL=$?
echo
}
force_reload() {
restart
}
rh_status() {
status $prog
}
rh_status_q() {
rh_status >/dev/null 2>&1
}
case $1 in
start)
rh_status_q && exit 0
$1
;;
stop)
rh_status_q || exit 0
$1
;;
restart)
$1
;;
reload)
rh_status_q || exit 7
$1
;;
force-reload)
force_reload
;;
status)
rh_status
;;
condrestart|try-restart)
rh_status_q || exit 0
;;
*)
echo $Usage: $0 {start|stop|status|restart|condrestart|try-restart|reload|force-reload}
exit 2
esac
3. 哨兵模式配置
3臺主機相同設置：
按照前面單redis安裝方法安裝程序；
創建相應數據目錄；
mkdir -p /usr/local/redis/data/redis
mkdir -p /usr/local/redis/data/sentinel
mkdir -p /usr/local/redis/sbin
vim /usr/local/redis/sbin/redis-server # 使用上文中的示例腳本
vim /usr/local/redis/sbin/redis-sentinel # 使用上文中的示例腳本
3.1 主redis配置
vim redis.conf
daemonize yes
pidfile /usr/local/redis/var/redis-server.pid
port 6379
tcp-backlog 128
timeout 0
tcp-keepalive 0
loglevel notice
logfile /usr/local/redis/var/redis-server.log
databases 16
save 900 1
save 300 10
save 60 10000
stop-writes-on-bgsave-error yes
rdbcompression yes
rdbchecksum yes
dbfilename dump.rdb
dir /usr/local/redis/data/redis
masterauth 20170310
requirepass 20170310
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
appendonly yes
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
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-entries 512
list-max-ziplist-value 64
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
群集文件配置 vim sentinel.conf
port 26379
pidfile /usr/local/redis/var/redis-sentinel.pid
dir /usr/local/redis/data/sentinel
daemonize yes
logfile /usr/local/redis/var/redis-sentinel.log
sentinel monitor mymaster 10.1.0.160 6379 2
sentinel parallel-syncs mymaster 2
sentinel auth-pass mymaster 20170310
3.2 從redis配置
相對主redis配置，多添加了如下行：
slaveof 10.1.0.160 6379
vim redis.conf
daemonize yes
pidfile /usr/local/redis/var/redis-server.pid
port 6379
tcp-backlog 128
timeout 0
tcp-keepalive 0
loglevel notice
logfile /usr/local/redis/var/redis-server.log
databases 16
save 900 1
save 300 10
save 60 10000
stop-writes-on-bgsave-error yes
rdbcompression yes
rdbchecksum yes
dbfilename dump.rdb
dir /usr/local/redis/data/redis
masterauth 20170310
requirepass 20170310
slaveof 10.1.0.160 6379
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 90
appendonly yes
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
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-entries 512
list-max-ziplist-value 64
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
vim sentinel.conf
port 26379
pidfile /usr/local/redis/var/redis-sentinel.pid
dir /usr/local/redis/data/sentinel
daemonize yes
logfile /usr/local/redis/var/redis-sentinel.log
sentinel monitor mymaster 10.1.0.160 6379 2
sentinel config-epoch mymaster 0
3.3 啟動redis和哨兵
啟動redis，主從都要啟動 /usr/local/redis/sbin/redis-server start
啟動群集監控，主從都要啟動 /usr/local/redis/sbin/redis-sentinel start
啟動報錯處理
錯誤1：
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.
解決方法(overcommit_memory)
1. `vim /etc/sysctl.conf`添加如下設置 , 然后`sysctl -p`
vm.overcommit_memory = 1
可選值：0、1、2。
0， 表示內核將檢查是否有足夠的可用內存供應用進程使用；如果有足夠的可用內存，內存申請允許；否則，內存申請失敗，并把錯誤返回給應用進程。
1， 表示內核允許分配所有的物理內存，而不管當前的內存狀態如何。
2， 表示內核允許分配超過所有物理內存和交換空間總和的內存
注意：redis在dump數據的時候，會fork出一個子進程，理論上child進程所占用的內存和parent是一樣的，比如parent占用 的內存為8G，這個時候也要同樣分配8G的內存給child,如果內存無法負擔，往往會造成redis服務器的down機或者IO負載過高，效率下降。所 以這里比較優化的內存分配策略應該設置為 1（表示內核允許分配所有的物理內存，而不管當前的內存狀態如何）。
這里又涉及到Overcommit和OOM。
什么是Overcommit和OOM？
在Unix中，當一個用戶進程使用malloc()函數申請內存時，假如返回值是NULL，則這個進程知道當前沒有可用內存空間，就會做相應的處理工作。許多進程會打印錯誤信息并退出。
Linux使用另外一種處理方式，它對大部分申請內存的請求都回復yes，以便能跑更多更大的程序。因為申請內存后，并不會馬上使用內存。這種技術叫做Overcommit。
當內存不足時，會發生OOM killer(OOM=out-of-memory)。它會選擇殺死一些進程(用戶態進程，不是內核線程)，以便釋放內存。
Overcommit的策略
Linux下overcommit有三種策略(Documentation/vm/overcommit-accounting)：
0. 啟發式策略。合理的overcommit會被接受，不合理的overcommit會被拒絕。
1. 任何overcommit都會被接受。
2. 當系統分配的內存超過swap N%*%u7269理RAM(N%%u7531vm.overcommit_ratio決定)時，會拒絕commit。
overcommit的策略通過vm.overcommit_memory設置。
overcommit的百分比由vm.overcommit_ratio設置。
# echo 2 > /proc/sys/vm/overcommit_memory
# echo 80 > /proc/sys/vm/overcommit_ratio
當oom-killer發生時，linux會選擇殺死哪些進程
選擇進程的函數是oom_badness函數(在mm/oom_kill.c中)，該函數會計算每個進程的點數(0~1000)。
點數越高，這個進程越有可能被殺死。
每個進程的點數跟oom_score_adj有關，而且oom_score_adj可以被設置(-1000最低，1000最高)。
錯誤2：
WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
echo 511 > /proc/sys/net/core/somaxconn
錯誤3：
16433:X 12 Jun 14:52:37.734 * Increased maximum number of open files to 10032 (it was originally set to 1024).
新裝的linux默認只有1024，當負載較大時，會經常出現error: too many open files
ulimit -a：使用可以查看當前系統的所有限制值
vim /etc/security/limits.conf
在文件的末尾加上
* soft nofile 65535
* hard nofile 65535
執行su或者重新關閉連接用戶再執行ulimit -a就可以查看修改后的結果。
故障切換機制
啟動群集之后，群集程序默認會在主從的sentinel.conf文件中加入群集信息
主：
port 26379
pidfile /usr/local/redis/var/redis-sentinel.pid
dir /usr/local/redis/data/sentinel
daemonize yes
logfile /usr/local/redis/var/redis-sentinel.log
sentinel myid aeff525d03a2234ef834808f7991761db03a1973
sentinel monitor mymaster 10.1.0.160 6379 2
sentinel parallel-syncs mymaster 2
sentinel auth-pass mymaster 20170310
# Generated by CONFIG REWRITE
sentinel config-epoch mymaster 0
sentinel leader-epoch mymaster 0
sentinel known-slave mymaster 10.1.0.71 6379
sentinel known-slave mymaster 10.1.0.161 6379
sentinel current-epoch 0
從1：
port 26379
pidfile /usr/local/redis/var/redis-sentinel.pid
dir /usr/local/redis/data/sentinel
daemonize yes
logfile /usr/local/redis/var/redis-sentinel.log
sentinel myid 01b1b7674abe648f6a2344fc5610e73b7e87cb8a
sentinel monitor mymaster 10.1.0.160 6379 2
sentinel config-epoch mymaster 0
# Generated by CONFIG REWRITE
sentinel leader-epoch mymaster 0
sentinel current-epoch 0
從2：
port 26379
pidfile /usr/local/redis/var/redis-sentinel.pid
dir /usr/local/redis/data/sentinel
daemonize yes
logfile /usr/local/redis/var/redis-sentinel.log
sentinel myid f1589f48079b3b3b536add4e2e01a36304aeba8c
sentinel monitor mymaster 10.1.0.160 6379 2
sentinel config-epoch mymaster 0
# Generated by CONFIG REWRITE
sentinel leader-epoch mymaster 0
sentinel current-epoch 0
模擬主故障
[root@show160 redis]# /usr/local/redis/bin/redis-cli -p 6379
127.0.0.1:6379> AUTH 20170310
OK
127.0.0.1:6379> DEBUG SEGFAULT
Could not connect to Redis at 127.0.0.1:6379: Connection refused
not connected> quit
從哨兵配置文件中可以看到當前的主庫的已經發生了改變
4. 總結
redis的哨兵端口26379使用redis-cli可以連接查看哨兵相關信息，要想連接此高可用redis，可使用官方的連接客戶端。使用哨兵監控當主故障后會自動切換從為主，當主啟動后就變成了從。至少要3哨兵和3redis節點才能允許掛一節點還能保證服務可用性。
參考資料：
https://redis.io/topics/sentinel
http://www.redis.cn/topics/sentinel.html
http://www.majunwei.com/view/201610302123020678.html
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