Varnish安装与配置实现负载均衡

Varnish概述

Varnish是一款高性能的开源HTTP加速器，其采用全新的软件体系机构，和现在的硬件体系紧密配合，与传统的 squid 相比，varnish 具有性能更高、速度更快、管理更加方便等诸多优点，很多大型的网站都开始尝试使用 varnish 来替换 squid，这些都促进 varnish 迅速发展起来。
Varnish 的作者Poul-Henning Kamp是FreeBSD的内核开发者之一，他认为现在的计算机比起1975年已经复杂许多。在1975年时，储存媒介只有两种：内存与硬盘。但现在计算机系统的内存除了主存外，还包括了CPU内的L1、L2，甚至有L3快取。硬盘上也有自己的快取装置，因此Squid Cache自行处理物件替换的架构不可能得知这些情况而做到最佳化，但操作系统可以得知这些情况，所以这部份的工作应该交给操作系统处理，这就是 Varnish cache设计架构。

varnish 安装与简单配置

下载 varnish 安装包（传送门：http://download.youkuaiyun.com/download/running_free/9978451），下载后放在自己方便使用的目录下

##server1
[root@server1 ~]# cd /software/
[root@server1 software]# ls
varnish-3.0.5-1.el6.x86_64.rpm  varnish-libs-3.0.5-1.el6.x86_64.rpm
[root@server1 software]# yum install -y *

简单配置与测试

[root@server1 software]# vim /etc/varnish/default.vcl
  7 backend web1 {
  8   .host = "172.25.27.2";
  9   .port = "80";
 10 }

[root@server1 software]# vim /etc/sysconfig/varnish

  7 # Maximum number of open files (for ulimit -n)
  8 NFILES=65535
  9 
 10 # Locked shared memory (for ulimit -l)
 11 # Default log size is 82MB + header
 12 MEMLOCK=64000
 13 
 14 # Maximum number of threads (for ulimit -u)
 15 NPROCS="unlimited"

 66 VARNISH_LISTEN_PORT=80

[root@server1 software]# vim /etc/security/limits.conf
 51 varnish -       nofile  65535
[root@server1 software]# service varnish start

##server2
[root@server2 ~]# service httpd start
Starting httpd: httpd: Could not reliably determine the server's fully qualified domain name, using 172.25.27.2 for ServerName
                                                           [  OK  ]
[root@server2 ~]# touch /var/www/html/index.html
[root@server2 ~]# echo "<h1>server 222222222</h1>">/var/www/html/index.html

##真机测试访问
解析
[root@foundation27 iso]# vim /etc/hosts
172.25.27.1     server1 www.redhat.org

[root@foundation27 iso]# curl 172.25.27.1
<h1>server 222222222</h1>
[root@foundation27 iso]# curl www.redhat.org
<h1>server 222222222</h1>


浏览器测试访问

查看缓存命中情况

###查看缓存命中情况

[root@server1 software]# vim /etc/varnish/default.vcl
sub vcl_deliver {
    if (obj.hits > 0) {
        set resp.http.X-Cache = "HIT from westos cache";
    }
    else {
        set resp.http.X-Cache = "MISS from westos cache";
    }
    return (deliver);
}
# service varnish reload

###测试缓存命中
###第一次为MISS，第二次以后为HIT

[root@foundation27 iso]# curl -I www.redhat.org
HTTP/1.1 200 OK
Server: Apache/2.2.15 (Red Hat)
Last-Modified: Thu, 14 Sep 2017 02:12:04 GMT
ETag: "200eb-1a-5591ccd7ba4b3"
Content-Type: text/html; charset=UTF-8
Content-Length: 26
Accept-Ranges: bytes
Date: Thu, 14 Sep 2017 02:39:26 GMT
X-Varnish: 1596377212
Age: 0
Via: 1.1 varnish
Connection: keep-alive
X-Cache: MISS from westos cache

[root@foundation27 iso]# curl -I www.redhat.org
HTTP/1.1 200 OK
Server: Apache/2.2.15 (Red Hat)
Last-Modified: Thu, 14 Sep 2017 02:12:04 GMT
ETag: "200eb-1a-5591ccd7ba4b3"
Content-Type: text/html; charset=UTF-8
Content-Length: 26
Accept-Ranges: bytes
Date: Thu, 14 Sep 2017 02:39:35 GMT
X-Varnish: 1596377213 1596377212
Age: 9
Via: 1.1 varnish
Connection: keep-alive
X-Cache: HIT from westos cache

通过 varnishadm 手动清除缓存

### 通过 varnishadm 手动清除缓存
# varnishadm ban.url .*$       #清除所有
# varnishadm ban.url /index.html    #清除 index.html 页面缓存
# varnishadm ban.url /admin/$      #清除 admin 目录缓存

定义多个不同域名站点的后端服务器

###定义多个不同域名站点的后端服务器
[root@server1 software]# vim /etc/varnish/default.vcl
backend web1 {
    .host = "172.25.27.2";
    .port = "80";
    }
backend web2 {
    .host = "172.25.27.3";
    .port = "80";
    }
#当访问 www.westos.org 域名时从 web1 上取数据,访问 bbs.westos.org 域名时到 web2 取数据,访问其他页面报错。
sub vcl_recv {
    if (req.http.host ~ "^(www.)?redhat.org") {
            set req.http.host = "www.redhat.org";
            set req.backend = web1;
        } elsif (req.http.host ~ "^bbs.redhat.org") {
            set req.backend = web2;
        } else {error 404 "redhat cache";
    }
}
# service varnish reload

[root@foundation27 iso]# vim /etc/hosts
172.25.27.1     server1 www.redhat.org bbs.redhat.org

[root@foundation27 iso]# curl bbs.redhat.org
<h1>server 333333333</h1>
[root@foundation27 iso]# curl www.redhat.org
<h1>server 222222222</h1>

浏览器测试访问

定义负载均衡

###定义负载均衡
[root@server1 software]# vim /etc/varnish/default.vcl
#定义健康检查     ##可不配置
probe healthcheck {
    .url = "/index.html"; # 哪个 url 需要 varnish 请求
    .interval = 5s; #检查的间隔时间
    .timeout = 1s; #等待多长时间探针超时
    .window = 5; #维持 5 个 sliding window 的结果
    .threshold = 3; #至少有三次 window 是成功的,就宣告 bachend 健康
    }

---------------------------------------------------------------------

backend web1 {
  .host = "172.25.27.2";
  .port = "80";
}

backend web2 {
        .host = "172.25.27.3";
        .port = "80";
        }

director lb round-robin {       #把多个后端聚合为一个组,并检测后端健康状况
        { .backend = web1; }
        { .backend = web2; }
}


sub vcl_recv {
        if (req.http.host ~ "^(www.)?redhat.org") {
                        set req.http.host = "www.redhat.org";
                        set req.backend = lb ;
                        return (pass);  #为了测试方便,不进行缓存。
                } elsif (req.http.host ~ "^bbs.redhat.org") {
                        set req.backend = web2;
                } else {error 404 "redhat cache";
        }
}

sub vcl_deliver {
        if (obj.hits > 0) {
                set resp.http.X-Cache = "HIT from redhat cache";
        }
        else {
                set resp.http.X-Cache = "MISS from redhat cache";
        }
        return (deliver);
}

# service varnish reload

浏览器第一次访问

第二次访问