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3台服务器Redis高可用哨兵模式@(学习)[redis, 高可用]
1. 介绍
环境
2. redis程序安装
以下是单redis安装脚本，可适用于单redis使用。
#!/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 ${sourcepackage_dir}/init.d/redis-server /etc/init.d/
/etc/init.d/redis-server start
chkconfig --add redis-server
chkconfig redis-server on
#################################################################################################
}
install_redis
redis启停脚本示例： cat redis-server
#!/bin/bash
#
# redis - this script starts and stops the redis-server daemon
#
# chkconfig: - 85 15
# description: Redis is a persistent key-value database
# processname: redis-server
# config: /usr/local/redis/etc/redis.conf
# config: /etc/sysconfig/redis
# pidfile: /usr/local/redis/var/redis-server.pid
# Source function library.
. /etc/rc.d/init.d/functions
# Source networking configuration.
. /etc/sysconfig/network
# Check that networking is up.
[ "$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: $0 {start|stop|status|restart|condrestart|try-restart|reload|force-reload}"
exit 2
esac
redis-sentinel启停脚本示例：
#!/bin/bash
#
# redis-sentinel - this script starts and stops the redis-server sentinel daemon
#
# chkconfig: - 85 15
# description: Redis sentinel
# processname: redis-server
# config: /usr/local/redis/etc/sentinel.conf
# config: /etc/sysconfig/redis
# pidfile: /usr/local/redis/var/redis-sentinel.pid
# Source function library.
. /etc/rc.d/init.d/functions
# Source networking configuration.
. /etc/sysconfig/network
# Check that networking is up.
[ "$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台主机相同设置： 1. 按照前面单redis安装方法安装程序； 2. 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 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 从redis配置相对主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 启动redis和哨兵启动redis，主从都要启动 /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 启动报错处理 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最低，1000最高)。 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。 故障切换机制
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 从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 从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 模拟主故障 [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 从哨兵配置文件中可以看到当前的主库的已经发生了改变 4. 总结redis的哨兵端口26379使用redis-cli可以连接查看哨兵相关信息，要想连接此高可用redis，可使用官方的连接客户端。使用哨兵监控当主故障后会自动切换从为主，当主启动后就变成了从。至少要3哨兵和3redis节点才能允许挂一节点还能保证服务可用性。 参考资料： https://redis.io/topics/sentinel http://www.redis.cn/topics/sentinel.html http://www.majunwei.com/view/201610302123020678.html |
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