自从动态生成缩略图上线后，NFS客户端日志时常报无法响应的错误，怀疑是NFS机IO过大，所以想到使用Varnish给NFS机减压，将缩略图存放到内存中，减少读的压力，然后就有了篇博文。 简介： 　　Varnish是一款高性能的开源HTTP加速器，网上评价比Squid更强，安装配置都很快速，方便。 
一、安装：

# wget http://repo.varnish-cache.org/source/varnish-2.1.5.tar.gz 
# tar zxvf varnish-2.1.5.tar.gz cd varnish-2.1.5 
# ./configure –prefix=/usr/local/varnish 
# make && make install

二、配置文件：

# cp /usr/local/varnish/etc/varnish/default.vcl /usr/local/varnish/etc/varnish/default.vcl.bak
# vi /usr/local/varnish/etc/varnish/default.vcl

# 反向代理请求的后端Web服务器ip和端口
backend default {
     .host = "192.168.1.1";
     .port = "80";
}

sub vcl_recv {
    if (req.request != "GET" && req.request != "HEAD") {
        return(pipe);
    } elseif(req.url ~ "\.(jpg|gif|png)$") {
        return (lookup);
    } else {
        return(pass);
    }
}

sub vcl_pipe {
    return (pipe);
}

sub vcl_pass {
    return (pass);
}

sub vcl_hash {
    set req.hash += req.url;
    if (req.http.host) {
        set req.hash += req.http.host;
    } else {
        set req.hash += server.ip;
    }
    return (hash);
}

sub vcl_hit {
    if (!obj.cacheable) {
        return (pass);
    }
    return (deliver);
}

sub vcl_miss {
    return (fetch);
}

sub vcl_fetch {
    if (beresp.http.Pragma ~ "no-cache" || 
        beresp.http.Cache-Control ~ "no-cache" || 
        beresp.http.Cache-Control ~ "private") {
          return (pass);
    }
   # 清除cookie，设置过期时间为30天
    if (req.request == "GET" && req.url ~ "\.(jpg|gif|png)$") {
        unset req.http.cookie;
        set beresp.ttl = 30d;
    }
    return (deliver);
}

sub vcl_deliver {
    # 增加标识(可使用firebug查看)x-hits，表示是否命中
    set resp.http.x-hits = obj.hits ;
    if (obj.hits > 0) {
       set resp.http.X-Cache = "h";
    } else {
       set resp.http.X-Cache = "m";
    }
}

三、启动：

# /usr/local/varnish/sbin/varnishd -f /usr/local/varnish/etc/varnish/default.vcl -n /var/log/varnish -s malloc,15G -w 300,51200,20 -T 127.0.0.1:2000 -a 0.0.0.0:8080

        说明：
                 -f 配置文件路径
             -n 主目录
             -s 分配 15G 内存
             -w 线程最小与最大数
             -T 管理IP和端口，可以使用telnet 127.0.0.1 2000 进行管理varnish
             -a 监听 8080 端口

四、写入日志文件：

# /usr/local/varnish/bin/varnishncsa -n /var/log/varnish -w /var/log/varnish/varnish.log

五、查看狀態：

# /usr/local/varnish/bin/varnishstat -n /var/log/varnish

六、關閉Varnish：

# pkill varnishd

七、清除緩存：

        1、清除指定域名：

/usr/local/varnish/bin/varnishadm -T 127.0.0.1:2000 purge "req.http.host ~ statics.xxx.com.tw"

        2、清除image目录下所有缓存：

/usr/local/varnish/bin/varnishadm -T 127.0.0.1:2000 url.purge /image/

        3、清除所有缓存：

/usr/local/varnish/bin/varnishadm -T 127.0.0.1:2000 url.purge *$

八、测试：
         ab测试：
                ab -c 100 -n 1000 http://x.x.x.x/129974432673506402_128x92.jpg
         未使用Varnish前：
                

Server Software:       nginx
Server Hostname:        x.x.x.x
Server Port:            8000

Document Path:          129974432673506402_128x92.jpg
Document Length:        2443 bytes

Concurrency Level:      100
Time taken for tests:   0.667390 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      2730000 bytes
HTML transferred:       2443000 bytes
Requests per second:    1498.37 [#/sec] (mean)
Time per request:       66.739 [ms] (mean)
Time per request:       0.667 [ms] (mean, across all concurrent requests)
Transfer rate:          3994.67 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.6      0       4
Processing:     2   61  23.2     57     248
Waiting:        1   60  23.2     57     247
Total:          2   61  23.1     58     248

Percentage of the requests served within a certain time (ms)
  50%     58
  66%     65
  75%     73
  80%     77
  90%     89
  95%    100
  98%    116
  99%    139
 100%    248 (longest request)

使用Varnish后：

Server Software:        nginx
Server Hostname:        p2.591.com.tw
Server Port:            8000

Document Path:          129974432673506402_128x92.jpg
Document Length:        2443 bytes

Concurrency Level:      100
Time taken for tests:   0.271769 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      2795675 bytes
HTML transferred:       2445443 bytes
Requests per second:    3679.60 [#/sec] (mean)
Time per request:       27.177 [ms] (mean)
Time per request:       0.272 [ms] (mean, across all concurrent requests)
Transfer rate:          10045.30 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    6   2.3      6      12
Processing:     1    7   2.3      7      17
Waiting:        1    6   2.1      7      15
Total:          3   13   1.7     14      23

Percentage of the requests served within a certain time (ms)
  50%     14
  66%     14
  75%     14
  80%     14
  90%     15
  95%     15
  98%     16
  99%     17
 100%     23 (longest request)

总结： 
        Varnish上线后，观察一段时间后，发现NFS报错的原因，尚未改善，现在把生成图片部分，换到NFS上，NFS报错出现的比较少，下一步，看换成千兆Switch后，再观察看看。

參考：
Varnish Cache + Riak
（http://blog.dloh.org/2011/01/varnish-cache-riak.html ）
varnish cache 反向代理服务器和http加速器的安装和配置
（http://blog.51yip.com/cache/618.html）
Varnish手冊
（http://www.varnish-cache.org/docs/2.1/tutorial/vcl.html）
varnish安装过程详解
（http://thinkgroupon.com/redirect.php?tid=3872&goto=lastpost）
使用Varnish代替Squid做网站缓存加速器的详细解决方案[原创]
（http://blog.s135.com/post/313/）
Varnish使用小结
（http://iyubo.blogbus.com/logs/35085709.html）