广州seo小雨
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。
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：
官方网站：
2、对于Centos 5的，可以执行以下命令来安装：
rpm –nosignature -i
yum install varnish
3、对于是Centos 6的，可以执行以下命令来安装：
rpm –nosignature -i
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) <= 4.6.0-1 is needed by varnish-release-3.0-1.el6.noarch
rpmlib(PayloadIsXz) <= 5.2-1 is needed by varnish-release-3.0-1.el6.noarch
Error: Missing Dependency: libedit.so.0 is needed by package varnish-3.0.5-1.el5.centos.i386 (varnish-3.0)
5、Centos 5安装时还会提示有依赖关系不能解决，解决的办法就是添加扩展的YUM 源，执行以下命令：
rpm -ivh （32位）
rpm -ivh （64位）
yum clean allyum update
6、对于是Debian系统，可以执行以下命令来安装：
curl | apt-key add -echo “deb wheezy varnish-3.0” >> /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 | sudo apt-key add -echo “deb precise varnish-3.0” | sudo tee -a /etc/apt/sources.listsudo
apt-get updatesudo
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
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：。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 <= 0s ||
beresp.http.Set-Cookie ||
beresp.http.Vary == “*”) {
/*
* Mark as “Hit-For-Pass” for the next 2 minutes
*/
set beresp.ttl = 120 s;
return (hit_for_pass);
}
set beresp.ttl = 1d;
return (deliver);
}
sub vcl_deliver {
return (deliver);
}
sub vcl_error {
set obj.http.Content-Type = “text/html; charset=utf-8”;
set obj.http.Retry-After = “5”;
synthetic {“
<?xml version=”1.0″ encoding=”utf-8″?>
<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Strict//EN”
“”>
<html>
<head>
<title>”} + obj.status + ” ” + obj.response + {“</title>
</head>
<body>
<h1>Error “} + obj.status + ” ” + obj.response + {“</h1>
<p>”} + obj.response + {“</p>
<h3>Guru Meditation:</h3>
<p>XID: “} + req.xid + {“</p>
<hr>
<p>Varnish cache server</p>
</body>
</html>
“};
return (deliver);
}
sub vcl_init {
return (ok);
}
sub vcl_fini {
return (ok);
}
2、下载下来的default.vcl你需要调整的地方有一处，就是将域名更改为自己要使用Varnish缓存的域名。
3、另外default.vcl还设置缓存时间，单位是s(秒)，h(小时),d(天)。
4、配置Varnish的访问端口。Varnish配置默认的访问端口不是80端口，因此需要修改/etc/sysconfig/varnish配置文件，把端口设置为80。
5、在/etc/sysconfig/varnish这个文件中还可以设置Varnish缓存大小，默认是1GB。
三、修改Apache和Nginx为非80端口
1、Varnish的端口改为了80后，我们需要将Apache和Nginx改为非80端口，一般地进入到Apache和Nginx的配置文件修改即可。
【如何企业网站优化】用Varnish和Memcached给WordPress网站提速