Talk Nginx + Keepalived (hot standby) to build high availability environment load balancing (HA) technique

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• A simple map that at about the meaning

• Keepalived to install CentOS virtual machine environment (two virtual machines are installed)

 The version used for the keepalived-1.2.24.tar.gz for easy mounting inside the system download well in advance of the relevant library

yum -y install libnl libnl-devel
yum install -y libnfnetlink-devel

And then began to unpack compile and install it

tar -zxvf  keepalived-1.2.24.tar.gz
cd  keepalived-1.2.24.tar.gz
./configure --prefix=/usr/local/keepalived
make
make install

Then continue to configure Keepalived

mkdir /etc/keepalived
cp /usr/local/keepalived/etc/keepalived.conf /etc/keepalived/keepalived.conf
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/keepalived
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/keepalived
添加到开机自启
chkconfig keepalived on


如果提示keepalived: command not found 解决方法如下
ln -s /usr/local/keepalived/sbin/keepalived /sbin/ 
如果遇权限不足 执行以下命令
chmod 755 /etc/init.d/keepalived


相关操作
service keepalived start   #启动服务
service keepalived stop    #停止服务
service keepalived restart #重启服务

请不要着急去启动Keepalived

• Keepalived profile comments

引用于http://blog.csdn.net/xyang81/article/details/52554398
keepalived服务安装完成之后，后面的主要工作就是在keepalived.conf文件中配置HA和负载均衡。
一个功能比较完整的常用的keepalived配置文件，主要包含三块：
全局定义块、VRRP实例定义块和虚拟服务器定义块。
全局定义块是必须的，如果keepalived只用来做ha，
虚拟服务器是可选的。下面是一个功能比较完整的配置文件模板：
#全局定义块
global_defs {
    # 邮件通知配置
    notification_email {
        email1
        email2
    }
    notification_email_from email
    smtp_server host
    smtp_connect_timeout num

    lvs_id string
    router_id string    ## 标识本节点的字条串,通常为hostname
}

#VRRP 实例定义块
vrrp_sync_group string { 
    group {
        string
        string
    }
}

vrrp_instance string {
    state MASTER|BACKUP
    virtual_router_id num
    interface string
    mcast_src_ip @IP 
    priority num
    advert_int num
    nopreempt
    smtp_alert
    lvs_sync_daemon_interface string 
    authentication {
        auth_type PASS|AH
        auth_pass string
    }

    virtual_ipaddress {  # Block limited to 20 IP addresses @IP
        @IP
        @IP
    }
}

#虚拟服务器定义块
virtual_server (@IP PORT)|(fwmark num) { 
    delay_loop num
    lb_algo rr|wrr|lc|wlc|sh|dh|lblc 
    lb_kind NAT|DR|TUN
    persistence_timeout num 
    protocol TCP|UDP
    real_server @IP PORT { 
        weight num
        notify_down /path/script.sh
        TCP_CHECK { 
            connect_port num 
            connect_timeout num
        }
    }

    real_server @IP PORT {
        weight num
        MISC_CHECK {
            misc_path /path_to_script/script.sh(or misc_path “/path_to_script/script.sh <arg_list>”)
        }
    }

    real_server @IP PORT {
        weight num
        HTTP_GET|SSL_GET {
            url { 
                # You can add multiple url block path alphanum
                digest alphanum
            }
            connect_port num
            connect_timeout num 
            nb_get_retry num 
            delay_before_retry num
        }
    }
}
全局定义块

1、email通知（notification_email、smtp_server、smtp_connect_timeout）：
用于服务有故障时发送邮件报警，可选项，不建议用。需要系统开启sendmail服务，
建议用第三独立监控服务，如用nagios全面监控代替。
2、lvs_id：lvs负载均衡器标识，在一个网络内，它的值应该是唯一的。
3、router_id：用户标识本节点的名称，通常为hostname
4、花括号｛｝：用来分隔定义块，必须成对出现。如果写漏了，
keepalived运行时不会得到预期的结果。由于定义块存在嵌套关系，
因此很容易遗漏结尾处的花括号，这点需要特别注意。
VRRP实例定义块

    vrrp_sync_group：同步vrrp级，用于确定失败切换（FailOver）包含的路由实例个数。
即在有2个负载均衡器的场景，一旦某个负载均衡器失效，需要自动切换到另外一个负载均衡器的实例是哪
    group：至少要包含一个vrrp实例，vrrp实例名称必须和vrrp_instance定义的一致
    vrrp_instance：vrrp实例名
    1> state：实例状态，只有MASTER 和 BACKUP两种状态，并且需要全部大写。
抢占模式下，其中MASTER为工作状态，BACKUP为备用状态。当MASTER所在的服务器失效时，
BACKUP所在的服务会自动把它的状态由BACKUP切换到MASTER状态。
当失效的MASTER所在的服务恢复时，BACKUP从MASTER恢复到BACKUP状态。
    2> interface：对外提供服务的网卡接口，即VIP绑定的网卡接口。
如：eth0，eth1。当前主流的服务器都有2个或2个以上的接口（分别对应外网和内网），在选择网卡接口时，一定要核实清楚。
    3> mcast_src_ip：本机IP地址
    4> virtual_router_id：虚拟路由的ID号，每个节点设置必须一样，
可选择IP最后一段使用，相同的 VRID 为一个组，他将决定多播的 MAC 地址。
    5> priority：节点优先级，取值范围0～254，MASTER要比BACKUP高
    6> advert_int：MASTER与BACKUP节点间同步检查的时间间隔，单位为秒
    7> lvs_sync_daemon_inteface：负载均衡器之间的监控接口,
类似于 HA HeartBeat 的心跳线。但它的机制优于 Heartbeat，因为它没有“裂脑”这个问题,
它是以优先级这个机制来规避这个麻烦的。在 DR 模式中，
lvs_sync_daemon_inteface与服务接口interface使用同一个网络接口
    8> authentication：验证类型和验证密码。类型主要有 PASS、AH 两种，通常使用PASS类型，
据说AH使用时有问题。验证密码为明文，同一vrrp 实例MASTER与BACKUP使用相同的密码才能正常通信。
    9> smtp_alert：有故障时是否激活邮件通知
    10> nopreempt：禁止抢占服务。默认情况，当MASTER服务挂掉之后，
BACKUP自动升级为MASTER并接替它的任务，当MASTER服务恢复后，
升级为MASTER的BACKUP服务又自动降为BACKUP，
把工作权交给原MASTER。当配置了nopreempt，
MASTER从挂掉到恢复，不再将服务抢占过来。
    11> virtual_ipaddress：虚拟IP地址池，可以有多个IP，每个IP占一行，不需要指定子网掩码。注意：这个IP必须与我们的设定的vip保持一致。

虚拟服务器virtual_server定义块

    virtual_server：定义一个虚拟服务器，这个ip是virtual_ipaddress中定义的其中一个，后面一个空格，然后加上虚拟服务的端口号。
    1> delay_loop：健康检查时间间隔，单位：秒
    2> lb_algo：负载均衡调度算法，互联网应用常用方式为wlc或rr
    3> lb_kind：负载均衡转发规则。包括DR、NAT、TUN 3种，一般使用路由（DR）转发规则。
    4> persistence_timeout：http服务会话保持时间，单位：秒
    5> protocol：转发协议，分为TCP和UDP两种
    real_server：真实服务器IP和端口，可以定义多个
    1> weight：负载权重，值越大，转发的优先级越高
    2> notify_down：服务停止后执行的脚本
    3> TCP_CHECK：服务有效性检测
    * connect_port：服务连接端口
    * connect_timeout：服务连接超时时长，单位：秒
    * nb_get_retry：服务连接失败重试次数
    * delay_before_retry：重试连接间隔，单位：秒

• Keepalived + Nginx configuration load balancing to achieve high availability

• IP server configuration information

VIP (Virtual IP)	IP	CPU name	Nginx port
192.168.110.138	192.168.110.128	nginx_master	80
192.168.110.138	192.168.110.130	nginx_backup	80

 To find out more venue: http: //freeloda.blog.51cto.com/2033581/1280962

Nginx is installed on a blog post has given

• Configuration Keepalived (preemptive mode configuration) increased VIP service to start

• MASTER (192.168.110.128) configuration information

global_defs {
   router_id nginx_master #hostname 
}
vrrp_script chk_nginx {
    script "/etc/keepalived/nginx_check.sh" #检测nginx的脚本
    interval 2                              #每2秒检测一次
    weight -20								#如果某一个nginx宕机 则权重减20
}
vrrp_instance VI_1 {
    state MASTER							#状态 MASTER BACKUP
    interface eth0							#绑定的网卡
    virtual_router_id 51                    #虚拟路由的ID号,两个节点设置必须一样
    mcast_src_ip 192.168.110.128            #本机的IP
    priority 90
    advert_int 1
# 设置验证信息，两个节点必须一致
    authentication {
        auth_type PASS
        auth_pass 1111
    }
 # 虚拟IP，两个节点设置必须一样。
    virtual_ipaddress {
        192.168.110.138
    }
# nginx存活状态检测脚本
    track_script {
       chk_nginx
    }
}

• BACKUP (192.168.110.130) configuration information

global_defs {
   router_id nginx_backup  #hostname 
}
vrrp_script chk_nginx {
    script "/etc/keepalived/nginx_check.sh" #检测nginx的脚本
    interval 2                              #每2秒检测一次
    weight -20								#如果某一个nginx宕机 则权重减20
}
vrrp_instance VI_1 {
    state BACKUP							#状态 MASTER BACKUP
    interface eth0							#绑定的网卡
    virtual_router_id 51
    mcast_src_ip 192.168.110.130
    priority 90
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.110.138
    }

    track_script {
       chk_nginx
    }
}

• Creating Nginx service detection script

原文地址http://blog.csdn.net/xyang81/article/details/52556886
#!/bin/bash
A=`ps -C nginx --no-header | wc -l`
if [ $A -eq 0 ];then
    /opt/nginx/sbin/nginx #尝试重新启动nginx
    sleep 2  #睡眠2秒
    if [ `ps -C nginx --no-header | wc -l` -eq 0 ];then
        killall keepalived #启动失败，将keepalived服务杀死。将vip漂移到其它备份节点
    fi
fi

• Start Keepalived service service keepalived start to see whether the MASTER bound VIP address

MASTER information (see IP 192.168.110.138 virtual server bound to the MASTER above)

BACKUP information

• MASTER manual close analog home server is down, the network information look

MASTER information (see Virtual IP does not exist proof has shifted the target host)

BACKUP information (virtual IP 192.168.110.138 been transferred to the BACKUP server)

• View project is normal, Session whether to share

Use virtual IP access log on right

Polling Tomcat server does not log in again

 

 

Redis is a unique Session

Conclusion:

All tests are only using a single project start-up test. Not test multi-project. Most entry without any difficulty and associated configuration specified parameters. If you want to meet their business to do. We would have to look carefully profile describes. Getting just a means of learning these techniques only. Not suitable for commercial application projects, specific to the actual business.

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