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cache.xml
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cache.xml
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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V5.0//EN"
"/usr/share/xml/docbook/schema/dtd/5.0/docbook.dtd" [
<!ENTITY article.author.xml SYSTEM "../common/article.author.xml">
<!ENTITY book.info.legalnotice.xml SYSTEM "../common/book.info.legalnotice.xml">
<!ENTITY book.info.abstract.xml SYSTEM "../common/book.info.abstract.xml">
]>
<article xml:base="http://netkiller.github.io/journal/cache.html"
xmlns="http://docbook.org/ns/docbook" xml:lang="zh-cn">
<articleinfo>
<title>实操 Web Cache</title>
<subtitle>http://netkiller.github.io/journal/cache.html</subtitle>
&article.author.xml;
<pubdate>$Date$</pubdate>
<releaseinfo>$Id$</releaseinfo>
&book.info.legalnotice.xml;
<abstract>
<para>写这篇文章的原因，是我看到网上很多谈这类的文章，多是人云亦云，不求实事，误导读者。</para>
<para>下面文中我会一个一个做实验，并展示给你，说明为什么会这样。只有自己亲自尝试才能拿出有说服力的真凭实据。</para>
<para>2014-03-12 首次发布</para>
<para>2015-08-27 修改，增加特殊数据缓存</para>
</abstract>
&book.info.abstract.xml;
<keywordset>
<keyword>If-Modified-Since, Last-Modified</keyword>
<keyword>ETag, If-None-Match</keyword>
<keyword></keyword>
</keywordset>
</articleinfo>
<section>
<title>测试环境</title>
<para>CentOS 6.5</para>
<para>Nginx安装脚本 https://github.com/oscm/shell/blob/master/nginx/nginx.sh</para>
<para>php安装脚本 https://github.com/oscm/shell/blob/master/php/5.5.8.sh</para>
</section>
<section id="modified">
<title>文件修改日期 If-Modified-Since / Last-Modified</title>
<para>If-Modified-Since 小于 Last-Modified 返回 HTTP/1.1 200 OK, 否则返回 HTTP/1.0 304 Not Modified</para>
<para>每次浏览器请求文件会携带 If-Modified-Since 头，将当前时间发送给服务器，与服务器的Last-Modified时间对对比，如果大于Last-Modified时间，返回HTTP/1.0 304 Not Modified不会重新打开文件，否则重新读取文件并返回内容</para>
<section>
<title>静态文件</title>
<para>nginx/1.0.15 静态文件自动产生 Last-Modified 头</para>
<screen>
# nginx -v
nginx version: nginx/1.0.15
# curl -I http://192.168.6.9/index.html
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 07:36:03 GMT
Content-Type: text/html
Content-Length: 6
Last-Modified: Thu, 27 Feb 2014 07:29:50 GMT
Connection: keep-alive
Accept-Ranges: bytes
</screen>
<para>图片文件</para>
<screen>
# curl -I http://192.168.6.9/image.png
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 07:37:18 GMT
Content-Type: image/png
Content-Length: 41516
Last-Modified: Thu, 27 Feb 2014 07:36:59 GMT
Connection: keep-alive
Accept-Ranges: bytes
</screen>
<tip>
<para>疑问 nginx/1.4.5 默认没有 Last-Modified</para>
<screen>
# nginx -v
nginx version: nginx/1.4.5
# curl -I http://192.168.2.15/index.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 02:13:44 GMT
Content-Type: text/html
Connection: keep-alive
</screen>
<para>经过一番周折最终找到答案 Nginx 如果开启 ssi 会禁用Last-Modified 关闭 ssi 后输出如下</para>
<screen>
# curl -I http://localhost/index.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 05:44:29 GMT
Content-Type: text/html
Content-Length: 6
Last-Modified: Wed, 25 Dec 2013 03:18:16 GMT
Connection: keep-alive
ETag: "52ba4e78-6"
Accept-Ranges: bytes
</screen>
<para></para>
</tip>
<para>再测试一次</para>
<screen>
# curl -H "If-Modified-Since: Fir, 28 Feb 2014 07:42:55 GMT" -I http://192.168.2.15/test.html
HTTP/1.1 304 Not Modified
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 02:34:54 GMT
Last-Modified: Fri, 28 Feb 2014 01:55:50 GMT
Connection: keep-alive
ETag: "530feca6-8b"
</screen>
<para>测试结果成功返回 HTTP/1.1 304 Not Modified， 但又莫名其妙的出现了 ETag。 这就是Nignx本版差异，非常混乱。</para>
<para>既然出现了ETag我们也顺便测试一下</para>
<screen>
# curl -H 'If-None-Match: "530feca6-8b"' -I http://192.168.2.15/test.html
HTTP/1.1 304 Not Modified
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 02:39:18 GMT
Last-Modified: Fri, 28 Feb 2014 01:55:50 GMT
Connection: keep-alive
ETag: "530feca6-8b"
</screen>
<para>也是成功的</para>
<para>测试图片</para>
<screen>
# curl -I http://localhost/logo.jpg
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 02:59:04 GMT
Content-Type: image/jpeg
Content-Length: 10103
Last-Modified: Fri, 28 Feb 2014 02:56:37 GMT
Connection: keep-alive
ETag: "530ffae5-2777"
Accept-Ranges: bytes
# curl -H 'If-None-Match: "530ffae5-2777"' -I http://localhost/logo.jpg
HTTP/1.1 304 Not Modified
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 03:03:33 GMT
Last-Modified: Fri, 28 Feb 2014 02:56:37 GMT
Connection: keep-alive
ETag: "530ffae5-2777"
# curl -H "If-Modified-Since: Fri, 28 Feb 2014 12:04:18 GMT" -I http://localhost/logo.jpg
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 03:04:45 GMT
Content-Type: image/jpeg
Content-Length: 10103
Last-Modified: Fri, 28 Feb 2014 02:56:37 GMT
Connection: keep-alive
ETag: "530ffae5-2777"
Accept-Ranges: bytes
</screen>
<para>测试结果，ETag通过测试，If-Modified-Since无论如何也无法返回 304 可能还需要其他的HTTP头，浏览器测试都通过返回 HTTP/1.1 304 Not Modified</para>
<para>现在换成浏览器测试 Chrome Firefox成功， 因为浏览器不会主动发送If-Modified-Since, 浏览器只有发现Last-Modified后，第二次请求才会推送 If-Modified-Since 需要刷新两次页面。</para>
<section>
<title>if_modified_since</title>
<para>在开启ssi的情况下，通过参数 if_modified_since 可以开启 Last-Modified</para>
<screen>
server {
listen 80;
server_name 192.168.2.15;
if_modified_since before;
}
</screen>
<para>测试结果看不到 Last-Modified, 因为 Nginx 的 if_modified_since before;参数只有接收到浏览器发过来的If-Modified-Since头才会发送Last-Modified</para>
<screen>
# curl -I http://192.168.2.15/test.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 02:39:42 GMT
Content-Type: text/html
Connection: keep-alive
</screen>
<para>最终 if_modified_since before; 数没有起到作用</para>
<para>参数设置为 if_modified_since exact;</para>
<screen>
# curl -I http://192.168.2.15/test.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 02:45:40 GMT
Content-Type: text/html
Connection: keep-alive
# curl -H 'If-None-Match: "530feca6-8b"' -I http://192.168.2.15/test.html
HTTP/1.1 304 Not Modified
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 02:45:44 GMT
Last-Modified: Fri, 28 Feb 2014 01:55:50 GMT
Connection: keep-alive
ETag: "530feca6-8b"
# curl -H "If-Modified-Since: Fir, 28 Feb 2014 07:42:55 GMT" -I http://192.168.2.15/test.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 02:45:50 GMT
Content-Type: text/html
Connection: keep-alive
</screen>
<para>测试失败，浏览器也是实测失败，ETag却成功</para>
</section>
</section>
<section>
<title>通过rewrite伪静态处理</title>
<para>index.php仍然是上面的那个php文件，我们只是做了伪静态</para>
<screen>
<![CDATA[
location / {
root /www;
index index.html index.htm;
rewrite ^/test.html$ /index.php last;
}
]]>
</screen>
<para>现在我们分别通过curl有chrome/firefox进行测试</para>
<screen>
<![CDATA[
# curl -H "If-Modified-Since: Fri, 28 Feb 2014 08:42:55 GMT" -I http://192.168.6.9/test.html
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 08:55:19 GMT
Content-Type: text/html
Connection: keep-alive
Last-Modified: Thu, 26 Feb 2014 08:39:35 GMT
]]>
</screen>
<para>经过测试无论是 curl 还是 chrome/firefox 均无法返回304.</para>
<para>下面是我的分析，仅供参考。用户请求index.html Nginx 会找到该文件读取 mtime 与 If-Modified-Since 匹配，如果If-Modified-Since大于 Last-Modified返回 304否则返回200.</para>
<para>为什么同样操作经过伪静态的test.html就不行呢？ 我分析当用户请求test.html Nginx 首先做Rewrite处理，然后跳转到index.php 整个过程nginx 并没有访问实际物理文件test.html也就没有mtime, 所以Nginx 返回200.</para>
<para>如果 Nginx 按预想的返回304，nginx 需要读取程序返回的HTTP头，Nginx 并没有这样的处理逻辑。</para>
</section>
<section>
<title>动态文件</title>
<para>动态文件没有 Last-Modified 头，我们可以伪造一个</para>
<screen>
<![CDATA[
# curl -I http://192.168.6.9/index.php
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 07:57:59 GMT
Content-Type: text/html
Connection: keep-alive
]]>
</screen>
<para>在程序中加入HTTP头推送操作,Last-Modified时间是27号，当前时间是28号，我们要让Last-Modified 小于当前时间才行。</para>
<screen>
<![CDATA[
# cat index.php
<?php
header('Last-Modified: Thu, 27 Feb 2014 08:39:35 GMT' );
//header('Last-Modified: ' .gmdate('D, d M Y H:i:s') . ' GMT' );
?>
Hello
]]>
</screen>
<para>现在你将看到 Last-Modified</para>
<screen>
<![CDATA[
# curl -I http://localhost/modified.php
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 05:59:28 GMT
Content-Type: text/html
Connection: keep-alive
Last-Modified: Fri, 28 Feb 2014 10:04:18 GMT
]]>
</screen>
<note>
<title>注意</title>
<para>虽然我们让动态程序返回了 Last-Modified ，但浏览器不认，经过测试 Chrome / Firefox 均不会承认.php文件，并缓存其内容。</para>
<screen>
<![CDATA[
# curl -I http://localhost/modified.php
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 05:59:28 GMT
Content-Type: text/html
Connection: keep-alive
Last-Modified: Fri, 28 Feb 2014 10:04:18 GMT
# curl -H "If-Modified-Since: Fri, 28 Feb 2014 08:42:55 GMT" -I http://localhost/modified.php
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Fri, 28 Feb 2014 05:32:30 GMT
Content-Type: text/html
Connection: keep-alive
Last-Modified: Thu, 26 Feb 2014 08:39:35 GMT
]]>
</screen>
<para>Last-Modified 对动态程序来说没有起到实际作用</para>
</note>
<para>Last-Modified是程序产生的，Nginx无法读到，让程序去处理状态返回是可行的，下面我们修改程序如下。</para>
<screen>
<![CDATA[
# cat modified.php
<?php
$mtime = 'Fri, 28 Feb 2014 12:04:18 GMT';
cache($mtime);
function cache($mtime)
{
$http_if_modified_since = null;
if(array_key_exists ('HTTP_IF_MODIFIED_SINCE',$_SERVER)){
$http_if_modified_since = $_SERVER['HTTP_IF_MODIFIED_SINCE'];
}
echo $http_if_modified_since;
if ($http_if_modified_since >= $mtime)
{
header('Last-Modified: '.$mtime, true, 304);
exit;
} else {
header('Last-Modified: ' . $mtime );
}
}
print_r($_SERVER);
echo date("Y-m-d H:i:s");
?>
]]>
</screen>
<para>测试效果</para>
<screen>
<![CDATA[
# curl -I http://localhost/modified.php
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 05:22:28 GMT
Content-Type: text/html
Connection: keep-alive
]]>
</screen>
<para>伪造一个 If-Modified-Since 日期小于我们指定的日期程序返回HTTP/1.1 200 OK</para>
<screen>
<![CDATA[
# curl -H "If-Modified-Since: Fri, 28 Feb 2014 10:04:18 GMT" -I http://localhost/modified.php
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 05:22:13 GMT
Content-Type: text/html
Connection: keep-alive
]]>
</screen>
<para>伪造一个 If-Modified-Since 日期大于我们指定的日期程序返回HTTP/1.1 304 Not Modified</para>
<screen>
<![CDATA[
# curl -H "If-Modified-Since: Fri, 28 Feb 2014 20:04:18 GMT" -I http://localhost/modified.php
HTTP/1.1 304 Not Modified
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 05:21:31 GMT
Connection: keep-alive
Last-Modified: Fri, 28 Feb 2014 12:04:18 GMT
]]>
</screen>
<para>测试成功，并且在浏览器端也测试成功 HTTP/1.1 304 Not Modified</para>
<para>将modified.php伪静态处理 </para>
<screen>
location / {
root /www;
index index.html index.htm;
rewrite ^/modified.html$ /modified.php last;
}
</screen>
<para>测试</para>
<screen>
# curl -I http://localhost/modified.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 06:21:10 GMT
Content-Type: text/html
Connection: keep-alive
Last-Modified: Fri, 28 Feb 2014 10:04:18 GMT
# curl -H "If-Modified-Since: Fri, 28 Feb 2014 12:04:18 GMT" -I http://localhost/modified.html
HTTP/1.1 304 Not Modified
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 06:21:22 GMT
Connection: keep-alive
Last-Modified: Fri, 28 Feb 2014 10:04:18 GMT
</screen>
<para>达到预期效果</para>
</section>
</section>
<section id="etag">
<title>ETag / If-None-Match</title>
<para>上面的Last-Modified测试中发现ETag虽然不限制，但是暗中还是可用的：）</para>
<para>etag on; 开启Nginx etag支持，lighttpd 默认开启</para>
<screen>
<![CDATA[
server {
listen 80;
server_name phalcon;
charset utf-8;
access_log /var/log/nginx/host.access.log main;
etag on;
location / {
root /www/phalcon/public;
index index.html index.php;
}
}
]]>
</screen>
<para>检查ETag输出</para>
<screen>
# curl -I http://localhost/index.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 03:08:28 GMT
Content-Type: text/html
Connection: keep-alive
# curl -I http://phalcon/img/css.png
HTTP/1.1 200 OK
Server: nginx
Date: Thu, 27 Feb 2014 09:20:49 GMT
Content-Type: image/png
Content-Length: 1133
Last-Modified: Fri, 14 Feb 2014 08:05:03 GMT
Connection: keep-alive
ETag: "52fdce2f-46d"
Accept-Ranges: bytes3
</screen>
<para>即使你开启了 ETag Nginx 对 HTML、CSS文件也不做处理。最终在一个外国网站是找到一个nginx-static-etags模块，有兴趣自己尝试，这里就不讲了。</para>
<section>
<title>静态文件</title>
<para>首先查询etag值</para>
<screen>
# curl -I http://phalcon/img/css.png
HTTP/1.1 200 OK
Server: nginx
Date: Thu, 27 Feb 2014 09:25:41 GMT
Content-Type: image/png
Content-Length: 1133
Last-Modified: Fri, 14 Feb 2014 08:05:03 GMT
Connection: keep-alive
ETag: "52fdce2f-46d"
Accept-Ranges: bytes
</screen>
<para>然后向服务器发送If-None-Match HTTP头</para>
<screen>
# curl -H 'If-None-Match: "52fdce2f-46d"' -I http://phalcon/img/css.png
HTTP/1.1 304 Not Modified
Server: nginx
Date: Thu, 27 Feb 2014 09:25:44 GMT
Last-Modified: Fri, 14 Feb 2014 08:05:03 GMT
Connection: keep-alive
ETag: "52fdce2f-46d"
</screen>
<para>这次比较顺利，成功返回HTTP/1.1 304 Not Modified</para>
</section>
<section>
<title>动态程序</title>
<para>默认情况输出如下</para>
<screen>
# curl -I http://192.168.6.9/index.php
HTTP/1.1 200 OK
Server: nginx
Date: Thu, 27 Feb 2014 09:29:13 GMT
Content-Type: text/html; charset=utf-8
Connection: keep-alive
</screen>
<para>测试程序</para>
<screen>
<![CDATA[
<?php
header('Last-Modified: Thu, 26 Feb 2014 08:39:35 GMT' );
header('Etag: "abcdefg"');
#header('Last-Modified: ' .gmdate('D, d M Y H:i:s') . ' GMT' );
?>
Hello
]]>
</screen>
<para>测试效果</para>
<screen>
# curl -I http://192.168.6.9/index.php
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 09:41:06 GMT
Content-Type: text/html
Connection: keep-alive
Last-Modified: Thu, 26 Feb 2014 08:39:35 GMT
Etag: "abcdefg"
[root@centos6 ~]# curl -H 'If-None-Match: "abcdefg"' -I http://192.168.6.9/index.php
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 09:41:42 GMT
Content-Type: text/html
Connection: keep-alive
Last-Modified: Thu, 26 Feb 2014 08:39:35 GMT
Etag: "abcdefg"
</screen>
<para>测试情况与之前的Last-Modified结果一样</para>
<para>动态程序返回Etag真的就没有用了吗？</para>
<para>答案是：非也， 有一个方法可以让动态程序返回的 Etag 也能发挥作用，程序修改如下</para>
<screen>
<![CDATA[
<?php
$etag = md5('http://netkiller.github.io');
cache($etag);
function cache($etag)
{
$http_if_none_match = null;
if(array_key_exists ('HTTP_IF_NONE_MATCH',$_SERVER)){
$http_if_none_match = $_SERVER['HTTP_IF_NONE_MATCH'];
}
if ($http_if_none_match == $etag)
{
header('Etag: '.$etag, true, 304);
exit;
} else {
header('Etag: '.$etag);
}
}
print_r($_SERVER);
echo date("Y-m-d H:i:s");
?>
]]>
</screen>
<para>首先查看Etag值</para>
<screen>
# curl -I http://192.168.6.9/test.php
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 10:07:19 GMT
Content-Type: text/html
Connection: keep-alive
Etag: 7467675324d0f7a3e01ce5151848fedb
</screen>
<para>发送If-None-Match头</para>
<screen>
# curl -H 'If-None-Match: 7467675324d0f7a3e01ce5151848fedb' -I http://192.168.6.9/test.php
HTTP/1.1 304 Not Modified
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 10:07:39 GMT
Connection: keep-alive
Etag: 7467675324d0f7a3e01ce5151848fedb
</screen>
<para>达成预计效果，此种方法同样可以用于 Last-Modified，伪静态后效果更好</para>
<para>Etag 值的运算技巧，我习惯上采用URL同时配合伪静态例如</para>
<screen>
$etag = $_SERVER['REQUEST_URI']
</screen>
<para>URL类似 http://www.example.com/news/100/1000.html 一次请求便缓存页面，这样带来一个更新的问题，于是又做了这样的处理</para>
<screen>
http://www.example.com/news/100/1000.1.html
</screen>
<para>.1.是版本号，每次修改后+1操作，.1.没有人格意义rewrite操作是会丢弃这个参数，仅仅是为了始终有新的URL对应内容</para>
</section>
</section>
<section id="expires">
<title>Expires / Cache-Control</title>
<para>前面所讲 Last-Modified 与 Etag 主要用于分辨文件是否修改过， 无法控制页面在浏览器端缓存的时间。Expires / Cache-Control 可以控制缓存的时间段</para>
<para>Expires 是 HTTP/1.0标准，Cache-Control是 HTTP/1.1标准。都能正常工作，HTTP/1.1规范中max-age优先级高于Expires,有些浏览器会联动设置，例如你设置了Cache-Control随之自动生成Expires，仅仅为了兼容。</para>
<section>
<title>静态文件</title>
<para>首先配置nginx设置html与png文件缓存1天</para>
<screen>
location ~ .*\.(html|png)$
{
expires 1d;
}
</screen>
<para>当前情况</para>
<screen>
# curl -I http://192.168.6.9/index.html
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 10:47:08 GMT
Content-Type: text/html
Content-Length: 6
Last-Modified: Thu, 27 Feb 2014 07:29:50 GMT
Connection: keep-alive
Accept-Ranges: bytes
</screen>
<para>重启Nginx后的HTTP协议头多出Expires与Cache-Control</para>
<screen>
# curl -I http://192.168.6.9/index.html
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 10:42:09 GMT
Content-Type: text/html
Content-Length: 3698
Last-Modified: Fri, 26 Apr 2013 20:36:51 GMT
Connection: keep-alive
Expires: Fri, 28 Feb 2014 10:42:09 GMT
Cache-Control: max-age=86400
Accept-Ranges: bytes
</screen>
</section>
<section>
<title>动态文件</title>
<para>默认返回</para>
<screen>
# curl -I http://192.168.6.9/index.php
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 11:45:05 GMT
Content-Type: text/html
Connection: keep-alive
</screen>
<para>index.php 增加 Cache-Control 输出控制</para>
<screen>
<![CDATA[
header('Cache-Control: max-age=259200');
]]>
</screen>
<para>再次查看</para>
<screen>
# curl -I http://192.168.6.9/index.php
HTTP/1.1 200 OK
Server: nginx/1.0.15
Date: Thu, 27 Feb 2014 11:53:48 GMT
Content-Type: text/html
Connection: keep-alive
Cache-Control: max-age=259200
</screen>
<para>现在使用 Chrome 、Firefox 测试，你会发现始终返回200，并且max-age=259200数值不会改变。</para>
<para>原因是Cache-Control程序输出的，Nginx并不知道，所以Nginx 不会给你返回304</para>
<screen>
<![CDATA[
header('Last-Modified: ' .gmdate('D, d M Y H:i:s') . ' GMT' );
$offset = 60 * 60 * 24;
header('Expires: ' . gmdate('D, d M Y H:i:s', time() + $offset) . ' GMT');
$ttl=3600;
header("Cache-Control: max-age=$ttl, must-revalidate");
]]>
</screen>
<para>这种方法不能实现缓存的目的</para>
</section>
</section>
<section id="fastcgi">
<title>FastCGI 缓存相关</title>
<para>我们做个尝试将 expires 1d;加到location ~ \.php$中，看看能不能实现缓存的目的。</para>
<screen>
location ~ \.php$ {
root /www;
fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME /www$fastcgi_script_name;
include fastcgi_params;
expires 1d;
}
</screen>
<para>测试程序</para>
<screen>
<![CDATA[
# cat expires.php
<?php
echo date("Y-m-d H:i:s");
?>
]]>
</screen>
<para>测试结果</para>
<screen>
# curl -I http://localhost/expires.php
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 04:39:57 GMT
Content-Type: text/html
Connection: keep-alive
Expires: Sat, 01 Mar 2014 04:39:57 GMT
Cache-Control: max-age=86400
</screen>
<para>虽然推送 Cache-Control: max-age=86400 但是 IE Chrome Firefox 仍不能缓存页面</para>
</section>
<section id="meta">
<title>HTML META 与 Cache</title>
<para>创建一个测试文件如下</para>
<screen>
<![CDATA[
<html>
<head>
<title>Hello</title>
<meta http-equiv="Cache-Control" content="max-age=7200" />
<meta http-equiv="expires" content="Fri, 28 Feb 2014 12:04:18 GMT" />
</head>
<body>
Helloworld
</body>
</html>
]]>
</screen>
<para>测试HTML页面</para>
<screen>
<![CDATA[
# curl -i http://localhost/test.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 03:30:45 GMT
Content-Type: text/html
Transfer-Encoding: chunked
Connection: keep-alive
<html>
<head>
<title>Hello</title>
<meta http-equiv="Cache-Control" content="max-age=7200" />
<meta http-equiv="expires" content="Fri, 28 Feb 2014 12:04:18 GMT" />
</head>
<body>
Helloworld
</body>
</html>
]]>
</screen>
<para>我们可以看到HTML页面中meta设置缓存对Nginx并不起作用, 很多人会说对浏览器起作用！</para>
<para>这次我测试了 IE11, Chrome, Firefox 发现都无法缓存页面，可能对IE5什么的还有用，我没有环境测试，因为10年前我们在B/S开发经常这样使用</para>
<screen>
<![CDATA[
<meta http-equiv="cache-control" content="max-age=0" />
<meta http-equiv="cache-control" content="no-cache" />
<meta http-equiv="expires" content="0" />
<meta http-equiv="expires" content="Tue, 01 Jan 1980 1:00:00 GMT" />
<meta http-equiv="pragma" content="no-cache" />
]]>
</screen>
<para>至少在当年IE是认这些Meta的，进入HTML5时代很多都发生了变化，所以不能一概而论</para>
</section>
<section id="gzip">
<title>gzip</title>
<para>defalte 是 Apache httpd 的标准这里只谈gzip</para>
<para>首先创建一个 gzip.html</para>
<screen>
# curl -I http://localhost/gzip.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Mon, 03 Mar 2014 01:49:45 GMT
Content-Type: text/html
Content-Length: 19644
Last-Modified: Mon, 03 Mar 2014 01:49:02 GMT
Connection: keep-alive
ETag: "5313df8e-4cbc"
Accept-Ranges: bytes
</screen>
<para>开启 gzip on;</para>
<screen>
server {
listen 80;
server_name localhost;
#charset utf-8;
#access_log /var/log/nginx/log/host.access.log main;
#etag on;
#ssi on;
gzip on;
</screen>
<para>现在看看效果</para>
<screen>
# curl -I http://localhost/gzip.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Mon, 03 Mar 2014 01:51:56 GMT
Content-Type: text/html
Content-Length: 19644
Last-Modified: Mon, 03 Mar 2014 01:49:02 GMT
Connection: keep-alive
ETag: "5313df8e-4cbc"
Accept-Ranges: bytes
</screen>
<para>并没有什么不同，现在增加HTTP头Accept-Encoding:gzip,defalte看看</para>
<screen>
<![CDATA[
# curl -H Accept-Encoding:gzip,defalte http://localhost/gzip.html
]]>
</screen>
<para>如果你能看到非文本内容（俗称乱码）就表示成功了。输入内容就是gzip压缩后二进制数据，我们使用gunzip可以解压缩</para>
<screen>
# curl -H Accept-Encoding:gzip,defalte http://localhost/gzip.html | gunzip
</screen>
<para>如果能正常看到html输出，表示压缩无误。</para>
<section>
<title>gzip 总结</title>
<para>gzip on; 开启后默认支持 text/html 不能在 gzip_types 再次定义，否则会提示重复MIME类型</para>
<screen>
Starting nginx: nginx: [warn] duplicate MIME type "text/html" in /etc/nginx/conf.d/localhost.conf:16
</screen>
<para>高级配置参考</para>
<screen>
gzip on;
gzip_http_version 1.0;
gzip_types text/plain text/xml text/css application/xml application/xhtml+xml application/rss+xml application/atom_xml application/javascript application/x-javascript application/json;
gzip_disable "MSIE [1-6]\.";
gzip_disable "Mozilla/4";
gzip_comp_level 6;
gzip_proxied any;
gzip_vary on;
gzip_buffers 4 8k;
gzip_min_length 1000;
</screen>
</section>
</section>
<section id="proxy">
<title>反向代理与缓存</title>
<para>反向代理服务器缓存方式分为：</para>
<para>强制缓存，指定文件，扩展名，URL设置缓存时间</para>
<para>遵循HTTP协议头标准进行缓存</para>
<para>默认配置，只进行代理，不进行缓存</para>
<screen>
server {
listen 80;
server_name 192.168.2.15;
#access_log /var/log/nginx/log/host.access.log main;
location / {
proxy_pass http://localhost:80;
proxy_set_header X-Real-IP $remote_addr;
}
}
</screen>
<para>反向代理会产生两条日志（access_log 写入一个文件中，如果分开写，则会分开写入日志）</para>
<screen>
192.168.2.15 - - [28/Feb/2014:18:09:33 +0800] "HEAD /modified.html HTTP/1.1" 200 0 "-" "curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.14.0.0 zlib/1.2.3 libidn/1.18 libssh2/1.4.2" "-"
127.0.0.1 - - [28/Feb/2014:18:09:33 +0800] "HEAD /modified.html HTTP/1.0" 200 0 "-" "curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.14.0.0 zlib/1.2.3 libidn/1.18 libssh2/1.4.2" "-"
</screen>
<para>Last-Modified 与 ETag 会透传过去</para>
<screen>
# curl -H "If-Modified-Since: Fri, 28 Feb 2014 12:04:18 GMT" -I http://192.168.2.15/modified.html
HTTP/1.1 304 Not Modified
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 10:17:30 GMT
Connection: keep-alive
Last-Modified: Fri, 28 Feb 2014 10:04:18 GMT
</screen>
<para>我们可以看到两条日志都返回304</para>
<screen>
192.168.2.15 - - [28/Feb/2014:18:17:30 +0800] "HEAD /modified.html HTTP/1.1" 304 0 "-" "curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.14.0.0 zlib/1.2.3 libidn/1.18 libssh2/1.4.2" "-"
127.0.0.1 - - [28/Feb/2014:18:17:30 +0800] "HEAD /modified.html HTTP/1.0" 304 0 "-" "curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.14.0.0 zlib/1.2.3 libidn/1.18 libssh2/1.4.2" "-"
</screen>
<para>下面为反向代理增加缓存功能</para>
<screen>
proxy_temp_path /tmp/proxy_temp_dir;
proxy_cache_path /tmp/proxy_cache_dir levels=1:2 keys_zone=nginx_cache:200m inactive=3d max_size=30g;
server {
listen 80;
server_name 192.168.2.15;
location / {
proxy_cache nginx_cache;
proxy_cache_key $host$uri$is_args$args;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_cache_valid 200 10m;
proxy_pass http://localhost;
}
location ~ .*\.(php|jsp|cgi)?$
{
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_pass http://backend_server;
}
}
</screen>
<para></para>
<screen>
# curl -I http://192.168.2.15/index.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 10:57:35 GMT
Content-Type: text/html
Content-Length: 12
Connection: keep-alive
Last-Modified: Fri, 28 Feb 2014 06:54:45 GMT
ETag: "531032b5-c"
Expires: Sat, 01 Mar 2014 10:57:35 GMT
Cache-Control: max-age=86400
Accept-Ranges: bytes
# curl -I http://192.168.2.15/index.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 10:57:41 GMT
Content-Type: text/html
Content-Length: 12
Connection: keep-alive
Last-Modified: Fri, 28 Feb 2014 06:54:45 GMT
ETag: "531032b5-c"
Expires: Sat, 01 Mar 2014 10:57:35 GMT
Cache-Control: max-age=86400
Accept-Ranges: bytes
# curl -I http://192.168.2.15/index.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Fri, 28 Feb 2014 10:57:46 GMT
Content-Type: text/html
Content-Length: 12
Connection: keep-alive
Last-Modified: Fri, 28 Feb 2014 06:54:45 GMT
ETag: "531032b5-c"
Expires: Sat, 01 Mar 2014 10:57:35 GMT
Cache-Control: max-age=86400
Accept-Ranges: bytes
</screen>
<para>上面共请求了3次服务器</para>
<screen>
192.168.2.15 - - [28/Feb/2014:18:57:35 +0800] "HEAD /index.html HTTP/1.1" 200 0 "-" "curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.14.0.0 zlib/1.2.3 libidn/1.18 libssh2/1.4.2" "-"
127.0.0.1 - - [28/Feb/2014:18:57:35 +0800] "GET /index.html HTTP/1.0" 200 12 "-" "curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.14.0.0 zlib/1.2.3 libidn/1.18 libssh2/1.4.2" "192.168.2.15"
192.168.2.15 - - [28/Feb/2014:18:57:41 +0800] "HEAD /index.html HTTP/1.1" 200 0 "-" "curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.14.0.0 zlib/1.2.3 libidn/1.18 libssh2/1.4.2" "-"
192.168.2.15 - - [28/Feb/2014:18:57:46 +0800] "HEAD /index.html HTTP/1.1" 200 0 "-" "curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.14.0.0 zlib/1.2.3 libidn/1.18 libssh2/1.4.2" "-"
</screen>
<para>第一次连接192.168.2.15然后转发给127.0.0.1 返回 HTTP/1.1 200 OK</para>
<para>后面两次连接192.168.2.15没有转发给127.0.0.1 直接返回 HTTP/1.1 200 OK</para>
<para>查看缓存目录,我们可以看到生成的缓存文件</para>
<screen>
# find /tmp/proxy_*
/tmp/proxy_cache_dir
/tmp/proxy_cache_dir/1
/tmp/proxy_cache_dir/1/79
/tmp/proxy_cache_dir/1/79/b47a0009c531900de2a15ba80c0e3791
/tmp/proxy_temp_dir
</screen>
<!-- proxy_ignore_headers Cache-Control; -->
<section id="proxy.gzip">
<title>gzip 处理</title>
<para>http://localhost/gzip.html 是支持压缩的，192.168.2.15 proxy_pass http://localhost</para>
<screen>
# curl -H Accept-Encoding:gzip,defalte http://localhost/gzip.html
</screen>
<para>运行后输出乱码</para>
<screen>
# curl -H Accept-Encoding:gzip,defalte http://192.168.2.15/gzip.html
</screen>
<para>现在透过反向代理请求试试，你会发现gzip压缩无效，输出的是HTML，这是怎么回事呢？这是因为反向代理不清楚后面的服务器是否支持gzip，所以一律按照正常html请求。现在我们开启 gzip_vary on; 每次返回数据会携带Vary: Accept-Encoding 头。</para>
<screen>
gzip on;
gzip_vary on;
</screen>
<para>reload nginx 后查看Vary: Accept-Encoding输出</para>
<screen>
# curl -I http://localhost/gzip.html
HTTP/1.1 200 OK
Server: nginx/1.4.5
Date: Mon, 03 Mar 2014 02:09:16 GMT
Content-Type: text/html
Content-Length: 19644
Last-Modified: Mon, 03 Mar 2014 01:49:02 GMT
Connection: keep-alive
Vary: Accept-Encoding
ETag: "5313df8e-4cbc"
Accept-Ranges: bytes
</screen>
<para>有 Vary: Accept-Encoding 头，现在再测试一次</para>
<screen>
<![CDATA[
# curl -H "Accept-Encoding: gzip" http://192.168.2.15/gzip.html
<html>
<head>
<title>Hello</title>
]]>
</screen>
<para>测试失败，并没有出现预期效果，于是到网站找答案，中文与英文资料都看个遍，没有解决.</para>
<para>最后只能让反向代理取到数据后再压缩一次，配置开启 gzip on;</para>
<screen>
proxy_temp_path /tmp/proxy_temp_dir;
proxy_cache_path /tmp/proxy_cache_dir levels=1:2 keys_zone=nginx_cache:200m inactive=3d max_size=30g;
server {
listen 80;
server_name 192.168.2.15;
gzip on;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
# proxy_set_header Accept-Encoding "gzip"; 没有任何效果
proxy_pass http://localhost;
}
}
</screen>
<para>Nginx 反向代理作为代理绰绰有余，如果做缓存服务器，还是使用squid, varnish吧。</para>
</section>
</section>
<section id="data">
<title>特殊数据缓存</title>
<para>缓存并非只能缓存静态内容，HTML,CSS,JS以及图片意外的数据一样可以缓存。</para>
<para>只要处理好HTTP头即可。例如Ajax动态内容缓存，JSON数据缓存。</para>
<section>
<title>json</title>
<para>当用户请求json地址时，我们将 json 数据附加HTTP头（Cache-Control, Expires, ETag），然后返回给用户，用户的设备会遵循HTTP的声明，进行缓存操作。</para>
<screen>
curl -I http://api.example.com/article/json/2/20/0.html