mysql【双主模式+haproxy+keepalived高可用】

说明

前文仅仅通过mysql双主 + keepalived实现高可用，这种方式在一台出现问题的时候可以切换，但是正常情况下只有一台服务使用，无法实现负载均衡，本文引入haproxy实现正常情况下也能有负载均衡的效果.

配置

1. 安装haproxy

yum install haproxy

2. 修改haproxy配置文件
   默认目录：/etc/haproxy/haproxy.cfg

#---------------------------------------------------------------------
# Example configuration for a possible web application.  See the
# full configuration options online.
#
#   http://haproxy.1wt.eu/download/1.4/doc/configuration.txt
#
#---------------------------------------------------------------------

#---------------------------------------------------------------------
# Global settings
#---------------------------------------------------------------------
global
    # to have these messages end up in /var/log/haproxy.log you will
    # need to:
    #
    # 1) configure syslog to accept network log events.  This is done
    #    by adding the '-r' option to the SYSLOGD_OPTIONS in
    #    /etc/sysconfig/syslog
    #
    # 2) configure local2 events to go to the /var/log/haproxy.log
    #   file. A line like the following can be added to
    #   /etc/sysconfig/syslog
    #
    #    local2.*                       /var/log/haproxy.log
    #
    log         127.0.0.1 local2

    chroot      /var/lib/haproxy
    pidfile     /var/run/haproxy.pid
    maxconn     4000
    user        haproxy
    group       haproxy
    daemon

    # turn on stats unix socket
    stats socket /var/lib/haproxy/stats

#---------------------------------------------------------------------
# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
#---------------------------------------------------------------------
defaults
    mode                    http
    log                     global
    option                  httplog
    option                  dontlognull
    option http-server-close
    option forwardfor       except 127.0.0.0/8
    option                  redispatch
    retries                 3
    timeout http-request    10s
    timeout queue           1m
    timeout connect         10s
    timeout client          1m
    timeout server          1m
    timeout http-keep-alive 10s
    timeout check           10s
    maxconn                 3000


######## 监控界面配置 #################
listen admin_status
        bind 0.0.0.0:8888
        mode http
        stats refresh 30s
        stats uri /
        stats realm welcome login\ Haproxy
        stats auth admin:123456
        stats hide-version
        stats admin if TRUE
        ########frontend配置##############

######## mysql负载均衡配置 ###############
listen mysql
        bind 0.0.0.0:13306
        mode tcp
        balance roundrobin                  # 负载均衡策略
        #option tcplog                      # tcp日志
        option mysql-check user haproxy     # 在mysql中创建无任何权限用户haproxy，且无密码
        server mysql_1 192.168.41.141:3306 check weight 1 maxconn 2000
        server mysql_2 192.168.41.142:3306 check weight 1 maxconn 2000
        option tcpka                        # 缺少这个配置,可能无法查看到数据库

option mysql-check user haproxy这里是配置健康检查的，需要在mysql中创建无任何权限用户haproxy，且无密码.

• CREATE USER 'haproxy'@'%' IDENTIFIED BY '';

3. 修改ulimit配置
   haproxy要求ulimit大于（maxconn*2 + 15 ）

#临时修改
ulimit -n 65536

#永久修改，需要修改/etc/security/limits.conf配置文件，文末增加以下内容，然后重新登录就可以生效
* soft nofile 65536
* hard nofile 65536
* soft nproc 65565
* hard nproc 65565

4. 启动服务并配置自启动

启动后访问8888端口，使用admin/123456登录就可以看到UI界面了。

systemctl start haproxy
systemctl enable haproxy

5. 修改keepalived配置
   前文配置的keepalived监控的是mysqld进程，需要修改成监控haproxy进程.这样不管哪台机器的mysql或者haproxy或者keepalived出现问题，都不影响使用.

# 修改的配置如下
vrrp_script chk_mysql {
    script "killall -0 haproxy"
    interval 2
    timeout 2
    fall 3
}

6. 测试
   通过VIP连接数据库，增删改查测试.