用Varnish和Memcached缓存给WordPress网站提速-内存级加速
http://www.freehao123.com/varnish-memcached/Varnish是一款高性能的缓存加速器，Varnish把数据存放在服务器的内存中，利用内存可以极大的提高PHP页面执行速度，可以设置0～60秒的精确缓存时间，32位的机器支持的缓存文件最大为2 GB。
Varnish采用VCL的配置，而且具有强大的管理功能，如top、stat、admin、lis，管理方式比较灵活。Varnish的状态机设计不仅巧妙，结构也很清晰，利用二叉堆管理缓存文件，即可达到随时删除的目的。
Memcached是一个高性能的分布式内存对象缓存系统，通过在内存中缓存数据和对象来减少读取数据库的次数，从而提高动态、数据库驱动网站的速度。Memcached对于减少MysqL数据查询压力非常有帮助。
由于Varnish采用了Visual Page Cache技术，所有缓存的数据都直接从内存读取，而Squid从硬盘读取缓存的数据，所以Varnish在访问速度方面会更快一些。但是Varnish在高并发状态下，CPU、I/O和内存等资源的开销高于Squid。
目前Varnish3.0版本解决了服务器重启后Varnish缓存消失的问题，性能优化上有了更大的提升。本篇文章就来分享一下利用Varnish和Memcached缓存来给Wordpress加速，因为要用到内存，所以比较适合那些大内存的服务器。
如果你正遭遇着大流量给Wordpress服务器带来的压力的苦恼，可以来尝试这些Wordpress提速方法：
[*] 1、Redis加速：用Redis缓存来给WordPress站点加速-适用于Apache和Nginx
[*] 2、负载均衡：免费空间+便宜VPS和OpenResty,Ngx_lua,Redis搭建系统负载均衡环境
[*] 3、CDN加速：DNSPOD分布式解析+安全宝和Incapsula对搜索引擎分别CDN加速
用Varnish和Memcached缓存给Wordpress网站提速-内存级加速
一、Varnish安装方法
1、Varnish官网：
[*] 1、官方网站：https://www.varnish-cache.org/
2、对于Centos 5的，可以执行以下命令来安装：
rpm --nosignature -i http://repo.varnish-cache.org/redhat/varnish-3.0/el5/noarch/varnish-release/varnish-release-3.0-1.el5.centos.noarch.rpm
yum install varnish
3、对于是Centos 6的，可以执行以下命令来安装：
rpm --nosignature -i http://repo.varnish-cache.org/redhat/varnish-3.0/el6/noarch/varnish-release/varnish-release-3.0-1.el6.noarch.rpm
yum install varnish
4、如果版本搞错，就会出现如下提示错误：
error: Failed dependencies: rpmlib(FileDigests)/etc/apt/sources.list
apt-get update
apt-get install varnish
6、对于是Ubuntu系统，可以执行以下命令来安装：
curl http://repo.varnish-cache.org/debian/GPG-key.txt | sudo apt-key add -
echo "deb http://repo.varnish-cache.org/ubuntu/ precise varnish-3.0" | sudo tee -a /etc/apt/sources.list
sudo apt-get update
sudo apt-get install varnish
7、设置Varnish开机启动，执行：chkconfig varnish on和chkconfig varnishncsa on
8、启动Varnish的命令是：service varnish start和service varnishncsa start
9、这里还有一个Linux+Nginx+MySQL+PHP+Varnish一键安装包，自动安装完成：Varnish高性能开源HTTP加速器:Varnish Nginx和Varnish Apache搭建配置。
二、Varnish相关配置
1、设置好Varnish缓存规则。默认是/etc/varnish/default.vcl，大家可以下载这个Varnish WordPress配置文件覆盖原来的，地址：http://centos.googlecode.com/files/default.vcl。源码内容：
# This is a basic VCL configuration file for varnish.See the vcl(7) # man page for details on VCL syntax and semantics.
# Default backend definition.Set this to point to your content
# server.
backend default {
.host = "127.0.0.1";
.port = "8080";
}
acl purge {
"localhost";
"127.0.0.1";
}
# Below is a commented-out copy of the default VCL logic.If you
# redefine any of these subroutines, the built-in logic will be
# appended to your code.
sub vcl_recv {
# Only cache the following site
if (req.http.host ~ "(amhg.freehao123.info)") {
set req.backend = default;
} else {
return (pass);
}
if (req.request == "PURGE") {
if (!client.ip ~ purge) {
error 405 "Not allowed.";
}
return (lookup);
}
if (req.restarts == 0) {
if (req.http.x-forwarded-for) {
set req.http.X-Forwarded-For =
req.http.X-Forwarded-For + ", " + client.ip;
} else {
set req.http.X-Forwarded-For = client.ip;
}
}
if (req.request != "GET" &&
req.request != "HEAD" &&
req.request != "PUT" &&
req.request != "POST" &&
req.request != "TRACE" &&
req.request != "OPTIONS" &&
req.request != "DELETE") {
/* Non-RFC2616 or CONNECT which is weird. */
return (pipe);
}
if (req.request != "GET" && req.request != "HEAD") {
/* We only deal with GET and HEAD by default */
return (pass);
}
if (req.http.Authorization || req.http.Cookie ~ "wordpress_logged" || req.http.Cookie ~ "comment_") {
/* Not cacheable by default */
return (pass);
}
return (lookup);
}
sub vcl_pipe {
# Note that only the first request to the backend will have
# X-Forwarded-For set.If you use X-Forwarded-For and want to
# have it set for all requests, make sure to have:
# set bereq.http.connection = "close";
# here.It is not set by default as it might break some broken web
# applications, like IIS with NTLM authentication.
return (pipe);
}
sub vcl_pass {
return (pass);
}
sub vcl_hash {
hash_data(req.url);
if (req.http.host) {
hash_data(req.http.host);
} else {
hash_data(server.ip);
}
return (hash);
}
sub vcl_hit {
if (req.request == "PURGE") {
purge;
error 200 "Purged.";
}
return (deliver);
}
sub vcl_miss {
if (req.request == "PURGE") {
purge;
error 200 "Purged.";
}
return (fetch);
}
sub vcl_fetch {
if (beresp.ttl
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