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這篇文章主要介紹“在流復制主備環境下怎么使用 HAProxy 搭建負載均衡環境”，在日常操作中，相信很多人在在流復制主備環境下怎么使用 HAProxy 搭建負載均衡環境問題上存在疑惑，丸趣 TV 小編查閱了各式資料，整理出簡單好用的操作方法，希望對大家解答”在流復制主備環境下怎么使用 HAProxy 搭建負載均衡環境”的疑惑有所幫助！接下來，請跟著丸趣 TV 小編一起來學習吧！
安裝
使用 yum 安裝相關軟件，在數據庫服務器上安裝 xinted 和 telnet
yum -y install xinetd telnet配置 xinetd
編寫識別主從庫的腳本 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 ]
/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 [ $VALUE == f ]
/bin/echo -e HTTP/1.1 200 OK\r\n
/bin/echo -e Content-Type: Content-Type: text/plain\r\n
/bin/echo -e \r\n
/bin/echo Primary
/bin/echo -e \r\n
/bin/echo -e HTTP/1.1 503 Service Unavailable\r\n
/bin/echo -e Content-Type: Content-Type: text/plain\r\n
/bin/echo -e \r\n
/bin/echo DB Down
/bin/echo -e \r\n
[pg12@localhost ~]$如為主庫，該腳本模擬接收 http 請求返回 http 200 響應，如為從庫則返回 206，如數據庫不可用則返回 503
# 主庫
[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
[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創建 xinetd 配置文件，端口使用 23267，指向剛才配置的 pgsqlchk 執行文件
[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
}添加服務，并啟動 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 $EXTRAOPTIONS (code=exited, status=0/SUCCESS)
Main PID: 2848 (xinetd)
CGroup: /system.slice/xinetd.service
└─2848 /usr/sbin/xinetd -stayalive -pidfile /var/run/xinetd.pid
[pg12@localhost ~]$檢查服務和監聽，（可通過設置 flags=IPv4 調整為監聽 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 ~]$配置 HAProxy with xinetd
在代理服務器上安裝 HAProxy
yum -y install haproxy telnet配置 HAProxy（/etc/haproxy/haproxy.cfg）
[pg12@localhost ~]$ 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 ~]$啟動 HAProxy
[pg12@localhost ~]$ sudo systemctl start haproxy
[pg12@localhost ~]$劃重點：
1.HAProxy 使用 TCP 模式而不是默認的 http 模式
2.HAProxy 監聽的端口是 5000-5001
3. 端口 5000 用于 RW 而 5001 用于 Read-only
4. 使用 http-check（端口為 23267）判斷狀態
5.pg0 可用于讀寫，pg1 僅用于讀
6. 基于 http-check，確定服務器狀態（根據服務響應確定：200/206/503）
驗證 haproxy 服務是否正常啟動，如出現 bind socket 的錯誤，則需調整內核參數和 SELinux 策略
1. 設置內核參數：net.ipv4.ip_nonlocal_bind=1
2. 設置 SELinux 策略
setsebool -P haproxy_connect_any=1
vim /etc/sysconfig/selinux
SELINUX=enforcing
SELINUX=permissive正常啟動 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 ~]#到此，關于“在流復制主備環境下怎么使用 HAProxy 搭建負載均衡環境”的學習就結束了，希望能夠解決大家的疑惑。理論與實踐的搭配能更好的幫助大家學習，快去試試吧！若想繼續學習更多相關知識，請繼續關注丸趣 TV 網站，丸趣 TV 小編會繼續努力為大家帶來更多實用的文章！
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