建站服务器 3台服务器Redis高可用哨兵模式
学习redis高可用
3台服务器Redis高可用哨兵模式
3.1 主redis配置
3.2 从redis配置
1. 介绍
2. redis程序安装
3. 哨兵模式配置
3.3 启动redis和哨兵
4. 总结
1. 介绍Redis Sentinel 是一个分布式系统， 你可以在一个架构中运行多个 Sentinel 进程（progress）， 这些进程使用流言协议（gossip protocols)来接收关于主服务器是否下线的信息， 并使用投票协议（agreement protocols）来决定是否执行自动故障迁移， 以及选择哪个从服务器作为新的主服务器。
虽然 Redis 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 Redis Sentinel 。
CentOS7.2
redis3.2.8
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
