3台服务器Redis高可用哨兵模式

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

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

#!/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

按照前面单redis安装方法安装程序；

创建相应数据目录；

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 # 使用上文中的示例脚本
vim /usr/local/redis/sbin/redis-sentinel # 使用上文中的示例脚本

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

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

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

/usr/local/redis/sbin/redis-server start
启动群集监控，主从都要启动
/usr/local/redis/sbin/redis-sentinel start

错误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.

解决方法(overcommit_memory)
1. `vim /etc/sysctl.conf`添加如下设置 , 然后`sysctl -p`
vm.overcommit_memory = 1
可选值：0、1、2。

0， 表示内核将检查是否有足够的可用内存供应用进程使用；如果有足够的可用内存，内存申请允许；否则，内存申请失败，并把错误返回给应用进程。
1， 表示内核允许分配所有的物理内存，而不管当前的内存状态如何。
2， 表示内核允许分配超过所有物理内存和交换空间总和的内存

注意：redis在dump数据的时候，会fork出一个子进程，理论上child进程所占用的内存和parent是一样的，比如parent占用 的内存为8G，这个时候也要同样分配8G的内存给child,如果内存无法负担，往往会造成redis服务器的down机或者IO负载过高，效率下降。所 以这里比较优化的内存分配策略应该设置为 1（表示内核允许分配所有的物理内存，而不管当前的内存状态如何）。
这里又涉及到Overcommit和OOM。

什么是Overcommit和OOM？
在Unix中，当一个用户进程使用malloc()函数申请内存时，假如返回值是NULL，则这个进程知道当前没有可用内存空间，就会做相应的处理工作。许多进程会打印错误信息并退出。
Linux使用另外一种处理方式，它对大部分申请内存的请求都回复yes，以便能跑更多更大的程序。因为申请内存后，并不会马上使用内存。这种技术叫做Overcommit。
当内存不足时，会发生OOM killer(OOM=out-of-memory)。它会选择杀死一些进程(用户态进程，不是内核线程)，以便释放内存。

Overcommit的策略
Linux下overcommit有三种策略(Documentation/vm/overcommit-accounting)：
0. 启发式策略。合理的overcommit会被接受，不合理的overcommit会被拒绝。
1. 任何overcommit都会被接受。
2. 当系统分配的内存超过swap+N%*物理RAM(N%由vm.overcommit_ratio决定)时，会拒绝commit。
overcommit的策略通过vm.overcommit_memory设置。
overcommit的百分比由vm.overcommit_ratio设置。

# echo 2 > /proc/sys/vm/overcommit_memory
# echo 80 > /proc/sys/vm/overcommit_ratio

当oom-killer发生时，linux会选择杀死哪些进程
选择进程的函数是oom_badness函数(在mm/oom_kill.c中)，该函数会计算每个进程的点数(0~1000)。
点数越高，这个进程越有可能被杀死。
每个进程的点数跟oom_score_adj有关，而且oom_score_adj可以被设置(-1000低，1000高)。

错误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

错误3：
16433:X 12 Jun 14:52:37.734 * Increased maximum number of open files to 10032 (it was originally set to 1024).

新装的linux默认只有1024，当负载较大时，会经常出现error: too many open files

ulimit -a：使用可以查看当前系统的所有限制值

vim /etc/security/limits.conf
在文件的末尾加上

* soft nofile 65535
* hard nofile 65535

执行su或者重新关闭连接用户再执行ulimit -a就可以查看修改后的结果。 

启动群集之后，群集程序默认会在主从的sentinel.conf文件中加入群集信息

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

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

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

[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

4. 总结

https://redis.io/topics/sentinel
http://www.redis.cn/topics/sentinel.html
http://www.majunwei.com/view/201610302123020678.html

名称栏目：3台服务器Redis高可用哨兵模式
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