HAProxy 高级应用(二）
概述：本章将继续介绍haproxy的一些其他应用，具体内容如下：
[*]use_backend <backend> 后端主机调用：
[*]haproxy中tcp模式的应用；
[*]haproxy中listen的应用
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HAProxy配置参数---代理配置段： 12.后端主机调用：
★use_backend <backend> [{if | unless} <condition>] ---Switch to a specific backend if/unless an ACL-based condition is matched.（满足acl条件时就调度到指定的后端主机）示例：
使用use_backend实现动静分离
HAProxy的tcp模式应用实验：
使用haproxy调度后端主机的SSH服务实验环境描述：
[*]三台虚拟主机，一台作为haproxy的调度器，另外两台作为后端的原始web服务器；
[*]haproxy调度器有两块网卡，一块作为外网网卡，负责接收用户的请求，一块为内网网卡，负责与内网的后端原始web服务器通信；（要打开核心件转发功能）
IP地址规划：
[*]两台后端主机使用内网地址RS1(192.168.111.128);RS2(192.168.111.129)，与haproxy的内网网卡基于VMnet1通信；
[*]haprosy外网地址ip（10.1.252.153）；内网地址ip(192.168.111.130)
实验过程如下：------------------------------------------------------------------------------------------------------ 1.编辑haproxy的配置文件，定义前端frontend和后端backend具体如下： frontend ssh
bind *:22022 //为了和本机区分使用22022
modetcp
default_backend sshsrvs
backend sshsrvs
balance leastconn //使用最少连接算法
serverssh1 192.168.111.128:22 check
serverssh2 192.168.111.129:22 check
2.重载haproxy服务，然后登录SSH服务，可以发现可以正常连接到后端的两台原始服务器，如下：
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# ssh -p 22022 10.1.252.153
The authenticity of host ':22022 (:22022)' can't be established.
ECDSA key fingerprint is cb:36:da:6b:15:d6:60:25:a7:28:f1:bf:b3:22:ce:c0.
Are you sure you want to continue connecting (yes/no)? yes
# ifconfig
eno16777736: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>mtu 1500
inet 192.168.111.129netmask 255.255.255.0broadcast 192.168.111.255
inet6 fe80::20c:29ff:feca:6ef1prefixlen 64scopeid 0x20<link>
ether 00:0c:29:ca:6e:f1txqueuelen 1000(Ethernet)
RX packets 156021bytes 13141000 (12.5 MiB)
RX errors 0dropped 0overruns 0frame 0
TX packets 24359bytes 1858526 (1.7 MiB)
TX errors 0dropped 0 overruns 0carrier 0collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING>mtu 65536
inet 127.0.0.1netmask 255.0.0.0
inet6 ::1prefixlen 128scopeid 0x10<host>
looptxqueuelen 0(Local Loopback)
RX packets 32bytes 2720 (2.6 KiB)
RX errors 0dropped 0overruns 0frame 0
TX packets 32bytes 2720 (2.6 KiB)
TX errors 0dropped 0 overruns 0carrier 0collisions 0
# exit
logout
Connection to 10.1.252.153 closed.
# ssh -p 22022 10.1.252.153
The authenticity of host ':22022 (:22022)' can't be established.
ECDSA key fingerprint is 56:78:d2:e8:41:b0:62:ad:4f:47:90:75:01:a4:fa:8c.
Are you sure you want to continue connecting (yes/no)? yes
# ifconfig
eno16777736: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>mtu 1500
inet 192.168.111.128netmask 255.255.255.0broadcast 192.168.111.255
inet6 fe80::20c:29ff:fed6:e460prefixlen 64scopeid 0x20<link>
ether 00:0c:29:d6:e4:60txqueuelen 1000(Ethernet)
RX packets 157051bytes 13309701 (12.6 MiB)
RX errors 0dropped 0overruns 0frame 0
TX packets 25174bytes 1963784 (1.8 MiB)
TX errors 0dropped 0 overruns 0carrier 0collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING>mtu 65536
inet 127.0.0.1netmask 255.0.0.0
inet6 ::1prefixlen 128scopeid 0x10<host>
looptxqueuelen 0(Local Loopback)
RX packets 59bytes 4880 (4.7 KiB)
RX errors 0dropped 0overruns 0frame 0
TX packets 59bytes 4880 (4.7 KiB)
TX errors 0dropped 0 overruns 0carrier 0collisions 0
HAProxy中listen的应用 1.如上例，我们也可以使用listen将两个单独的forontend和backend整合到一起，如下： listen ssh
bind *:22022
modetcp
balance leastconn
serverssh1 192.168.111.128:22 check
serverssh2 192.168.111.129:22 check
2.我们也可以将stats统计信息状态页使用listen整合到一起，如下：
listen stats
bind *:9527
stats enable
stats uri /admin?stats
stats realm Stats\ Page\ Area
stats auth taotao:xiuxiu
stats refresh 5s
stats hide-version
3.重载haproxy服务，查看监听的端口9527，如下：
# systemctl reload haproxy.service
# ss -tnl
State Recv-Q Send-Q Local Address:Port
LISTEN 0 128 127.0.0.1:6012
LISTEN 0 25 *:514
LISTEN 0 128 *:22022
LISTEN 0 128 *:8080
LISTEN 0 128 *:80
LISTEN 0 128 *:22
LISTEN 0 128 *:9527
4.在浏览器中访问stats统计页状态信息如下：
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