一、简介Nginx版本从0.7.48开始,支持了类似Squid的缓存功能。这个缓存是把URL及相关组合当做Key,用md5算法对Key进行哈希，得到硬盘上对应的哈希目录路径，从而将缓存内容保存在该目录内。
Nginx Web 缓存服务只能为指定URL或状态码设置过期时间，不支持类似Squid的PURGE指令手动清除缓存；但是我们可以通过Nginx的模块ngx_cache_purge清除指定URL的缓存。
PRoxy_cache：缓存后端服务器的内容，可能是任何内容，包括静态的和动态，减少了nginx与后端通信的次数，节省了传输时间和后端宽带fastcgi_cache：缓存fastcgi生成的内容，很多情况是php生成的动态的内容，少了nginx与php的通信的次数，更减轻了php和数据库(MySQL)的压力，这比用memcached之类的缓存要轻松得多
图片来自网络
二、配置nginx.conf
fastcgi_cache_path /var/run/nginx-cache levels=1:2 keys_zone=WordPRESS:100m inactive=60m;
fastcgi_cache_key "$scheme$request_method$host$request_uri";
fastcgi_cache_use_stale error timeout invalid_header http_500;
fastcgi_ignore_headers Cache-Control Expires Set-Cookie;
fastcgi_temp_path /tmp/nginx/fcgi/temp;
vhost配置
server {
server_name example.com www.example.com;access_log /var/log/nginx/example.com.access.log;
error_log /var/log/nginx/example.com.error.log;
root /var/www/example.com/htdocs;
index index.php;
set $skip_cache 0;
# POST requests and urls with a query string should always go to PHP
if ($request_method = POST) {
set $skip_cache 1;
}
if ($query_string != "") {
set $skip_cache 1;
}
# Don't cache uris containing the following segments
if ($request_uri ~* "/wp-admin/|/xmlrpc.php|wp-.*.php|/feed/|index.php|sitemap(_index)?.xml") {
set $skip_cache 1;
}
# Don't use the cache for logged in users or recent commenters
if ($http_cookie ~* "comment_author|wordpress_[a-f0-9]+|wp-postpass|wordpress_no_cache|wordpress_logged_in") {
set $skip_cache 1;
}
location / {
try_files $uri $uri/ /index.php?$args;
}
location ~ \.php($|/) {
try_files $uri =404;
include fastcgi_params;
fastcgi_split_path_info ^(.+\.php)(/.+)$;
fastcgi_param PATH_INFO $fastcgi_path_info;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_pass unix:/dev/shm/php-socket;
fastcgi_cache_bypass $skip_cache;
fastcgi_no_cache $skip_cache;
fastcgi_cache WORDPRESS;
include fcgi_cache_params;
}
location ~ /purge(/.*) {
fastcgi_cache_purge WORDPRESS "$scheme$request_method$host$1";
}
location ~* ^.+\.(ogg|ogv|svg|svgz|eot|otf|woff|mp4|ttf|rss|atom|jpg|jpeg|gif|png|ico|zip|tgz|gz|rar|bz2|doc|xls|exe|PPT|tar|mid|midi|wav|bmp|rtf)$ {
access_log off;log_not_found off; expires max;
}
location = /robots.txt { access_log off; log_not_found off; }
location ~ /\. { deny all; access_log off; log_not_found off; }
}
fcgi_cache_params配置
#include fcgi_cache_params;
#fastcgi_cache_valid 200 302 1s;
### fcgi-cache
fastcgi_cache fcgi;
fastcgi_cache_valid 200 302 1s;
fastcgi_cache_valid 404 500 502 503 504 0s;
fastcgi_cache_valid any 1m;
fastcgi_cache_min_uses 1;
fastcgi_cache_use_stale error timeout invalid_header http_500 http_503 updating;
fastcgi_ignore_headers Cache-Control Expires Set-Cookie;
#add_header X-Cache "$upstream_cache_status - $upstream_response_time";
fastcgi_cache_key "$scheme$request_method$host$request_uri"
大概解释下各个参数的含义：
fastcgi_cache 该指令用于设置哪个缓存区将被使用，zone_name的值为fastcgi_cache_path指令创建的缓存名称
fastcgi_cache_path 作用域：http
fastcgi_cache_path path
[levels=levels] [use_temp_path=on|off] keys_zone=name:size [inactive=time]
[max_size=size] [loader_files=number] [loader_sleep=time] [loader_threshold=time]
[purger=on|off] [purger_files=number] [purger_sleep=time] [purger_threshold=time];
该指令用于设置缓存文件的存放路径，示例如下：fastcgi_cache_path /data/nginx/cache levels=1:2 keys_zone=cache_one:100M inactive=1d max_size=10g;
a、levels:指定了该缓存空间有两层hash目录，设置缓存目录层数，levels=1:2，表示创建两层目录缓存，最多创建三层。第一层目录名取fastcgi_cache_key md5的最后一个字符，第二层目录名取倒数2-3字符，如：fastcgi_cache_key md5为b7f54b2df7773722d382f4809d65029c，则：
levels=1:2为/data/nginx/cache/c/29/b7f54b2df7773722d382f4809d65029c
levels=1:2:3为/data/nginx/cache/c/29/650/b7f54b2df7773722d382f4809d65029c
b、keys_zone为这个缓存区起名为zone_name,500m指代缓存空间为500MB;
c、inactive=1d 代表如果缓存文件一天内没有被访问，则删除;
d、max_size=30g代表硬盘缓存最大为30G;
设置缓存多个磁盘fastcgi_cache_path /path/to/hdd1 levels=1:2 keys_zone=my_cache_hdd1:10m max_size=10g inactive=60m use_temp_path=off;
fastcgi_cache_path /path/to/hdd2 levels=1:2 keys_zone=my_cache_hdd2:10m max_size=10g inactive=60m use_temp_path=off;
split_clients $request_uri $my_cache {
50% "my_cache_hdd1";
50% "my_cache_hdd2";
}
server {
...
location / {
fastcgi_cache $my_cache;
}
}
将缓存文件放入内存中编辑/etc/fstab 或者 放入 /dev/shm
tmpfs /etc/nginx/cache tmpfs defaults,size=100M 0 0
mount -a
df -ah | grep tmpfs
需要注意的是fastcgi_cache缓存是先写在fastcgi_temp_path再移到fastcgi_cache_path，所以这两个目录最好在同一个分区，从0.8.9之后可以在不同的分区，不过还是建议放同一分区
fastcgi_cache_methods 该指令用于设置缓存哪些HTTP方法，默认缓存HTTP GET/HEAD方法。
fastcgi_cache_min_uses URL经过多少次请求将被缓存
fastcgi_cache_valid reply_code [reply_code ... ] time
该指令用于对不同返回状态码的URL设置不同的缓存时间，例如：
fastcgi_cache_valid 200 302 10m;
fastcgi_cache_valid 404 1m;
设置202 302状态URL缓存10分钟，404状态的URL缓存1分钟。
注意：如果不指定状态码，直接指定缓存时间，则只有200,301,302状态码会进行缓存。
fastcgi_cache_valid 5m;
any 可以指定缓存任何响应码
fastcgi_cache_valid 200 302 10m;
fastcgi_cache_valid 301 1h;
fastcgi_cache_valid any 1m;
缓存的参数也可以在响应头直接设置。这些的优先级高于缓存时间设定使用该指令
The “X-Accel-Expires” header field sets caching time of a response in seconds. The zero value disables caching for a response. If the value starts with the @ prefix, it sets an absolute time in seconds since Epoch, up to which the response may be cached.If the header does not include the “X-Accel-Expires” field, parameters of caching may be set in the header fields “Expires” or “Cache-Control”.If the header includes the “Set-Cookie” field, such a response will not be cached.If the header includes the “Vary” field with the special value “*”, such a response will not be cached (1.7.7). If the header includes the “Vary” field with another value, such a response will be cached taking into account the corresponding request header fields (1.7.7).fastcgi_cache_key
该指令用来设置Web缓存的Key值，Nginx根据Key值MD5缓存。一般根据$host(域名),$request_uri(请求的路径)等变量组合成fastcgi_cache_key。
例如：fastcgi_cache_key "$scheme$request_method$host$request_uri";
定义fastcgi_cache的key，示例中就以请求的URI作为缓存的key，Nginx会取这个key的md5作为缓存文件，如果设置了缓存哈希目录，Nginx会从后往前取相应的位数做为目录。
注意一定要加上$request_method作为cache key，否则如果HEAD类型的先请求会导致后面的GET请求返回为空
fastcgi_temp_path path [level1 [level2 [level3]]]; 默认为 fastcgi_temp;
该指令用来设置fastcgi_cache临时文件目录
fastcgi_temp_path /spool/nginx/fastcgi_temp 1 2;
a temporary file might look like this:
/spool/nginx/fastcgi_temp/7/45/00000123457
fastcgi_cache_use_stale : fastcgi_cache_use_stale error | timeout | invalid_header | updating | http_500 | http_503 | http_403 | http_404 | off ...;
定义哪些情况下用过期缓存
x-cache头，用于调试$upstream_response_time为过期时间
$upstream_cache_status 变量表示此请求响应来自cache的状态，几种状态分别为：
MISS– The response was not found in the cache and so was fetched from an origin server. The response might then have been cached.BYPASS– The response was fetched from the origin server instead of served from the cache because the request matched a proxy_cache_bypass directive (see Can I Punch a Hole Through My Cache? below.) The response might then have been cached.EXPIRED– The entry in the cache has expired. The response contains fresh content from the origin server.STALE– The content is stale because the origin server is not responding correctly, and proxy_cache_use_stale was configured.UPDATING– The content is stale because the entry is currently being updated in response to a previous request, and proxy_cache_use_stale updating is configured.REVALIDATED– The proxy_cache_revalidate directive was enabled and NGINX verified that the current cached content was still valid (If-Modified-Since or If-None-Match).HIT– The response contains valid, fresh content direct from the cache.有一些情况会影响到cache的命中 这里需要特别注意
Nginx fastcgi_cache在缓存后端fastcgi响应时，当响应里包含“set-cookie”时，不缓存;当响应头包含Expires时，如果过期时间大于当前服务器时间，则nginx_cache会缓存该响应，否则，则不缓存;当响应头包含Cache-Control时，如果Cache-Control参数值为no-cache、no-store、private中任意一个时，则不缓存，如果Cache-Control参数值为max-age时，会被缓存，且nginx设置的cache的过期时间，就是系统当前时间 + mag-age的值。header("Expires: ".gmdate("D, d M Y H:i:s", time()+10000).' GMT');
header("Expires: ".gmdate("D, d M Y H:i:s", time()-99999).' GMT');
header("X-Accel-Expires:5"); // 5s
header("Cache-Control: no-cache"); //no cache
header("Cache-Control: no-store"); //no cache
header("Cache-Control: private"); //no cache
header("Cache-Control: max-age=10"); //cache 10s
setcookie('hello',"testaaaa"); //no cache
注意session使用的时候有坑，可以用下面来设置
session_cache_limiter("none");
session_start();
echo date("Y-m-d H:i:s",time());
可以看一下PHP源代码中的头信息 Expires等//ext/session/session.c line:1190 左右
// ...
CACHE_LIMITER_FUNC(private) /* {{{ */
{
ADD_HEADER("Expires: Thu, 19 Nov 1981 08:52:00 GMT");
CACHE_LIMITER(private_no_expire)(TSRMLS_C);
}
/* }}} */
//再到这里3 或者上面几个 ##默认是nocache
CACHE_LIMITER_FUNC(nocache) /* {{{ */
{
ADD_HEADER("Expires: Thu, 19 Nov 1981 08:52:00 GMT");
/* For HTTP/1.1 conforming clients and the rest (MSIE 5) */
ADD_HEADER("Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0");
/* For HTTP/1.0 conforming clients */
ADD_HEADER("Pragma: no-cache");
}
/* }}} */
//这里2
static php_session_cache_limiter_t php_session_cache_limiters[] = {
CACHE_LIMITER_ENTRY(public)
CACHE_LIMITER_ENTRY(private)
CACHE_LIMITER_ENTRY(private_no_expire)
CACHE_LIMITER_ENTRY(nocache)
{0}
};
static int php_session_cache_limiter(TSRMLS_D) /* {{{ */
{
php_session_cache_limiter_t *lim;
if (PS(cache_limiter)[0] == '\0') return 0;
if (SG(headers_sent)) {
const char *output_start_filename = php_output_get_start_filename(TSRMLS_C);
int output_start_lineno = php_output_get_start_lineno(TSRMLS_C);
if (output_start_filename) {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "Cannot send session cache limiter - headers already sent (output started at %s:%d)", output_start_filename, output_start_lineno);
} else {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "Cannot send session cache limiter - headers already sent");
}
return -2;
}
for (lim = php_session_cache_limiters; lim->name; lim++) {
if (!strcasecmp(lim->name, PS(cache_limiter))) {
lim->func(TSRMLS_C); //这里1
return 0;
}
}
return -1;
}
三、清除缓存NGINX只在商业版中支持proxy_cache_purge指令清除缓存，开源的ngx_cache_purge模块只支持单一key的缓存清除。为了实现按目录清除缓存只能自己开发。
NGINX作为Cache服务器时将资源内容以文件形式进行缓存，缓存元信息存储于共享内存中，组织成一棵红黑树。红黑树中的每个节点代表一个Cache元信息。NGINX将Cache Key的HASH值作为红黑树节点的KEY。内容缓存文件以该HASH值作为文件名存储在磁盘上。
NGINX的处理流程简化描述是这样的：当请求到达时，根据Cache Key的HASH值在红黑树中进行查找。如果找到，并查看相关信息，如果Cache可用，返回相应的Cache文件。否则，则回源抓取。
因为元信息是以Cache Key的HASH值作为Key存储的，因而红黑树中并不能保留Cache Key中有层级关系. 如”/uri/foo”和”/uri/bar”在元信息红黑树中完全没有关系。要实现按照目录清除缓存，需要将Cache Key中层次关系存储起来。
可以这样做，在共享内存中建立一棵目录树来存储层级关系。将Cache Key类比于文件系统中的路径, 每级路径存储为树中的一个节点。当需要清除某一目录下的所有缓存时，将该节点子树的中的所有缓存清除即可。
安装Purge模块Purge模块被用来清除缓存
wget http://labs.frickle.com/files/ngx_cache_purge-1.2.tar.gz
tar -zxvf ngx_cache_purge-1.2.tar.gz
编译
./configure \
…… \
--with-http_geoip_module \
--add-module=/usr/local/ngx_cache_purge-1.2
四、需要注意的一些问题设置了之后重启nginx就可以生效了，这个时候再访问php的页面的话，就会被缓存了，可以查看/var/logs/nginx/fastcgi_cache_dir这个目录下面是有缓存文件的。最后再说明一点，如果更改了缓存目录的路径，一定要把缓存的名称也改掉，后端调用的名称也同步改掉，如果只改掉了缓存目录，不改缓存名称的话，缓存的时候还是会缓存到之前的路径下面去，但是调用的时候调用的是新的路径，这个时候就会出现找不到的情况
参考文章
http://www.nginxtips.com/configure-nginx-fastcgi-cache/
http://www.haidx.com/fastcgi-cache-details.html
http://www.just4coding.com/blog/2014/11/01/nginx-purge-directory/
http://weizhifeng.net/nginx-proxy-cache.html
https://www.nginx.com/blog/nginx-caching-guide/#gs.6PdbraI
http://nginx.org/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_cache
https://www.cnxct.com/several-reminder-in-nginx-fastcgi_cache-and-php-session_cache_limiter/
https://rtcamp.com/wordpress-nginx/tutorials/single-site/fastcgi-cache-with-purging/
http://nginx.org/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_cache