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PostgreSQL DBA(128) - pgAdmin(Load balance with HAProxy)

原创 PostgreSQL 作者:husthxd 时间:2019-11-14 17:45:36 0 删除 编辑

本文简单介绍了在流复制主备环境下如何使用HAProxy搭建负载均衡环境。

安装
使用yum安装相关软件,在数据库服务器上安装xinted和telnet

yum -y install xinetd telnet

配置xinetd
编写识别主从库的脚本pgsqlchk

[pg12@localhost ~]$ cat pgsqlchk 
#!/bin/bash
# This script checks if a postgres server is healthy running on localhost. It will return:
# "HTTP/1.x 200 OK\r" (if postgres is running smoothly)
# - OR -
# "HTTP/1.x 500 Internal Server Error\r" (else)
# The purpose of this script is make haproxy capable of monitoring postgres properly
# It is recommended that a low-privileged postgres  user is created to be used by this script.
# For eg. create  user healthchkusr login password 'hc321';
PGBIN=/appdb/pg12/pg12.0/bin
PGSQL_HOST="localhost"
PGSQL_PORT="5432"
PGSQL_DATABASE="testdb"
PGSQL_USERNAME="pg12"
export PGPASSWORD="root"
TMP_FILE="/tmp/pgsqlchk.out"
ERR_FILE="/tmp/pgsqlchk.err"
# We perform a simple query that should return a few results
VALUE=`$PGBIN/psql -qt -h localhost -U pg12 -p 5432 -c "select pg_is_in_recovery()" 2> /dev/null`
# Check the output. If it is not empty then everything is fine and we return something. Else, we just do not return anything.
if [ $VALUE == "t" ]
then
    /bin/echo -e "HTTP/1.1 206 OK\r\n"
    /bin/echo -e "Content-Type: Content-Type: text/plain\r\n"
    /bin/echo -e "\r\n"
    /bin/echo "Standby"
    /bin/echo -e "\r\n"
elif [ $VALUE == "f" ]
then
    /bin/echo -e "HTTP/1.1 200 OK\r\n"
    /bin/echo -e "Content-Type: Content-Type: text/plain\r\n"
    /bin/echo -e "\r\n"
    /bin/echo "Primary"
    /bin/echo -e "\r\n"
else
    /bin/echo -e "HTTP/1.1 503 Service Unavailable\r\n"
    /bin/echo -e "Content-Type: Content-Type: text/plain\r\n"
    /bin/echo -e "\r\n"
    /bin/echo "DB Down"
    /bin/echo -e "\r\n"
fi
[pg12@localhost ~]$

如为主库,该脚本模拟接收http请求返回http 200响应,如为从库则返回206,如数据库不可用则返回503

#主库
[pg12@localhost ~]$ ifconfig | grep 'inet'
        inet 192.168.26.28  netmask 255.255.0.0  broadcast 192.168.255.255
        ...
[pg12@localhost ~]$ ./pgsqlchk 
HTTP/1.1 200 OK
Content-Type: Content-Type: text/plain
Primary
#从库
[pg12@localhost ~]$ ifconfig | grep 'inet'
        inet 192.168.26.25  netmask 255.255.0.0  broadcast 192.168.255.255
        ...
[pg12@localhost ~]$ ./pgsqlchk 
HTTP/1.1 206 OK
Content-Type: Content-Type: text/plain
Standby

创建xinetd配置文件,端口使用23267,指向刚才配置的pgsqlchk执行文件

[pg12@localhost ~]$ cat /etc/xinetd.d/pgsqlchk
service pgsqlchk
{
        flags           = REUSE
        socket_type     = stream
        port            = 23267
        wait            = no
        user            = nobody
        server          = /home/pg12/pgsqlchk
        log_on_failure  += USERID
        disable         = no
        only_from       = 0.0.0.0/0
        per_source      = UNLIMITED
}

添加服务,并启动xinetd

[pg12@localhost ~]$ sudo bash -c 'echo "pgsqlchk 23267/tcp # pgsqlchk" >> /etc/services'
[pg12@localhost ~]$ sudo systemctl start xinetd
[pg12@localhost ~]$ systemctl status xinetd
● xinetd.service - Xinetd A Powerful Replacement For Inetd
   Loaded: loaded (/usr/lib/systemd/system/xinetd.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2019-11-14 12:04:37 CST; 23s ago
  Process: 2847 ExecStart=/usr/sbin/xinetd -stayalive -pidfile /var/run/xinetd.pid $EXTRAOPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 2848 (xinetd)
   CGroup: /system.slice/xinetd.service
           └─2848 /usr/sbin/xinetd -stayalive -pidfile /var/run/xinetd.pid
[pg12@localhost ~]$

检查服务和监听,(可通过设置flags=IPv4调整为监听IPv4地址)

[pg12@localhost ~]$ sudo netstat -antup | grep 23267
tcp6       0      0 :::23267                :::*                    LISTEN      6837/xinetd
[pg12@localhost ~]$ sudo systemctl restart xinetd
[pg12@localhost ~]$ sudo systemctl status xinetd -l
● xinetd.service - Xinetd A Powerful Replacement For Inetd
   Loaded: loaded (/usr/lib/systemd/system/xinetd.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2019-11-14 15:43:49 CST; 6s ago
  Process: 7461 ExecStart=/usr/sbin/xinetd -stayalive -pidfile /var/run/xinetd.pid $EXTRAOPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 7462 (xinetd)
   CGroup: /system.slice/xinetd.service
           └─7462 /usr/sbin/xinetd -stayalive -pidfile /var/run/xinetd.pid
Nov 14 15:43:49 localhost.localdomain xinetd[7462]: START: pgsqlchk pid=7463 from=192.168.26.26
Nov 14 15:43:49 localhost.localdomain xinetd[7462]: EXIT: pgsqlchk status=0 pid=7463 duration=0(sec)
Nov 14 15:43:52 localhost.localdomain xinetd[7462]: START: pgsqlchk pid=7465 from=192.168.26.26
Nov 14 15:43:52 localhost.localdomain xinetd[7462]: EXIT: pgsqlchk status=0 pid=7465 duration=0(sec)
Nov 14 15:43:52 localhost.localdomain xinetd[7462]: START: pgsqlchk pid=7466 from=192.168.26.26
Nov 14 15:43:52 localhost.localdomain xinetd[7462]: EXIT: pgsqlchk status=0 pid=7466 duration=0(sec)
Nov 14 15:43:55 localhost.localdomain xinetd[7462]: START: pgsqlchk pid=7467 from=192.168.26.26
Nov 14 15:43:55 localhost.localdomain xinetd[7462]: EXIT: pgsqlchk status=0 pid=7467 duration=0(sec)
Nov 14 15:43:55 localhost.localdomain xinetd[7462]: START: pgsqlchk pid=7468 from=192.168.26.26
Nov 14 15:43:55 localhost.localdomain xinetd[7462]: EXIT: pgsqlchk status=0 pid=7468 duration=0(sec)
[pg12@localhost ~]$ sudo netstat -antup | grep 23267
tcp        0      0 0.0.0.0:23267           0.0.0.0:*               LISTEN      7462/xinetd         
[pg12@localhost ~]$

配置HAProxy with xinetd
在代理服务器上安装HAProxy

yum -y install haproxy telnet

配置HAProxy(/etc/haproxy/haproxy.cfg)

[pg12@localhost ~]$ cat /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 http-server-close
    option forwardfor       except 127.0.0.0/8
    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
listen stats
    mode http
    bind *:7000
    stats enable
    stats uri /
listen ReadWrite
    bind *:5000
    option httpchk
    http-check expect status 200
    default-server inter 3s fall 3 rise 2 on-marked-down shutdown-sessions
    server pg0 pg0:5432 maxconn 100 check port 23267
listen ReadOnly
    bind *:5001
    option httpchk
    http-check expect status 206
    default-server inter 3s fall 3 rise 2 on-marked-down shutdown-sessions
    server pg0 pg0:5432 maxconn 100 check port 23267
    server pg1 pg1:5432 maxconn 100 check port 23267
[pg12@localhost ~]$

启动HAProxy

[pg12@localhost ~]$ sudo systemctl start haproxy
[pg12@localhost ~]$

划重点:
1.HAProxy使用TCP模式而不是默认的http模式
2.HAProxy监听的端口是5000-5001
3.端口5000用于RW而5001用于Read-only
4.使用http-check(端口为23267)判断状态
5.pg0可用于读写,pg1仅用于读
6.基于http-check,确定服务器状态(根据服务响应确定:200/206/503)

验证haproxy服务是否正常启动,如出现bind socket的错误,则需调整内核参数和SELinux策略


1.设置内核参数:
net.ipv4.ip_nonlocal_bind=1
2.设置SELinux策略
setsebool -P haproxy_connect_any=1
vim /etc/sysconfig/selinux
SELINUX=enforcing
-->
SELINUX=permissive

正常启动HAProxy的日志

[root@localhost ~]# systemctl status haproxy -l
● haproxy.service - HAProxy Load Balancer
   Loaded: loaded (/usr/lib/systemd/system/haproxy.service; disabled; vendor preset: disabled)
   Active: active (running) since Thu 2019-11-14 14:41:09 CST; 12min ago
 Main PID: 1963 (haproxy-systemd)
   CGroup: /system.slice/haproxy.service
           ├─1963 /usr/sbin/haproxy-systemd-wrapper -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid
           ├─1964 /usr/sbin/haproxy -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid -Ds
           └─1965 /usr/sbin/haproxy -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid -Ds
Nov 14 14:41:09 localhost.localdomain systemd[1]: Started HAProxy Load Balancer.
Nov 14 14:41:09 localhost.localdomain haproxy-systemd-wrapper[1963]: haproxy-systemd-wrapper: executing /usr/sbin/haproxy -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid -Ds
[root@localhost ~]#

负载均衡
to be continued

参考资料
PostgreSQL Application Connection Failover Using HAProxy with xinetd

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