【nginx】關于fastcgi_cache

2024-06-28 14:33:11

字體：大中小

來源：轉載

供稿：網友

一、簡介

Nginx版本從0.7.48開始,支持了類似Squid的緩存功能。這個緩存是把URL及相關組合當做Key,用md5算法對Key進行哈希，得到硬盤上對應的哈希目錄路徑，從而將緩存內容保存在該目錄內。

Nginx Web 緩存服務只能為指定URL或狀態碼設置過期時間，不支持類似Squid的PURGE指令手動清除緩存；但是我們可以通過Nginx的模塊ngx_cache_purge清除指定URL的緩存。

PRoxy_cache：緩存后端服務器的內容，可能是任何內容，包括靜態的和動態，減少了nginx與后端通信的次數，節省了傳輸時間和后端寬帶
fastcgi_cache：緩存fastcgi生成的內容，很多情況是php生成的動態的內容，少了nginx與php的通信的次數，更減輕了php和數據庫(MySQL)的壓力，這比用memcached之類的緩存要輕松得多

圖片來自網絡

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-cachefastcgi_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"

大概解釋下各個參數的含義：

fastcgi_cache 該指令用于設置哪個緩存區將被使用，zone_name的值為fastcgi_cache_path指令創建的緩存名稱

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];

該指令用于設置緩存文件的存放路徑，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:指定了該緩存空間有兩層hash目錄，設置緩存目錄層數，levels=1:2，表示創建兩層目錄緩存，最多創建三層。第一層目錄名取fastcgi_cache_key md5的最后一個字符，第二層目錄名取倒數2-3字符，如：fastcgi_cache_key md5為b7f54b2df7773722d382f4809d65029c，則：

levels=1:2為/data/nginx/cache/c/29/b7f54b2df7773722d382f4809d65029clevels=1:2:3為/data/nginx/cache/c/29/650/b7f54b2df7773722d382f4809d65029c

b、keys_zone為這個緩存區起名為zone_name,500m指代緩存空間為500MB;

c、inactive=1d 代表如果緩存文件一天內沒有被訪問，則刪除;

d、max_size=30g代表硬盤緩存最大為30G;

設置緩存多個磁盤

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;           }}

將緩存文件放入內存中

編輯/etc/fstab 或者放入 /dev/shm

tmpfs /etc/nginx/cache tmpfs defaults,size=100M 0 0mount -adf -ah | grep tmpfs

需要注意的是fastcgi_cache緩存是先寫在fastcgi_temp_path再移到fastcgi_cache_path，所以這兩個目錄最好在同一個分區，從0.8.9之后可以在不同的分區，不過還是建議放同一分區

fastcgi_cache_methods 該指令用于設置緩存哪些HTTP方法，默認緩存HTTP GET/HEAD方法。

fastcgi_cache_min_uses URL經過多少次請求將被緩存

fastcgi_cache_valid reply_code [reply_code ... ] time

該指令用于對不同返回狀態碼的URL設置不同的緩存時間，例如：　

fastcgi_cache_valid 200 302 10m;fastcgi_cache_valid 404      1m;

設置202 302狀態URL緩存10分鐘，404狀態的URL緩存1分鐘。

注意：如果不指定狀態碼，直接指定緩存時間，則只有200,301,302狀態碼會進行緩存。

fastcgi_cache_valid 5m;

any 可以指定緩存任何響應碼　　　　

fastcgi_cache_valid 200 302 10m;fastcgi_cache_valid 301      1h;fastcgi_cache_valid any      1m;

緩存的參數也可以在響應頭直接設置。這些的優先級高于緩存時間設定使用該指令

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

該指令用來設置Web緩存的Key值，Nginx根據Key值MD5緩存。一般根據$host(域名),$request_uri(請求的路徑)等變量組合成fastcgi_cache_key。

例如：fastcgi_cache_key "$scheme$request_method$host$request_uri";

定義fastcgi_cache的key，示例中就以請求的URI作為緩存的key，Nginx會取這個key的md5作為緩存文件，如果設置了緩存哈希目錄，Nginx會從后往前取相應的位數做為目錄。

注意一定要加上$request_method作為cache key，否則如果HEAD類型的先請求會導致后面的GET請求返回為空

fastcgi_temp_path path [level1 [level2 [level3]]]; 默認為 fastcgi_temp;

該指令用來設置fastcgi_cache臨時文件目錄

fastcgi_temp_path /spool/nginx/fastcgi_temp 1 2;

a temporary file might look like this:

/spool/nginx/fastcgi_temp/7/45/00000123457

定義哪些情況下用過期緩存

x-cache頭，用于調試

$upstream_response_time為過期時間

$upstream_cache_status 變量表示此請求響應來自cache的狀態，幾種狀態分別為：

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.

有一些情況會影響到cache的命中這里需要特別注意

Nginx fastcgi_cache在緩存后端fastcgi響應時，當響應里包含“set-cookie”時，不緩存;
當響應頭包含Expires時，如果過期時間大于當前服務器時間，則nginx_cache會緩存該響應，否則，則不緩存;
當響應頭包含Cache-Control時，如果Cache-Control參數值為no-cache、no-store、private中任意一個時，則不緩存，如果Cache-Control參數值為max-age時，會被緩存，且nginx設置的cache的過期時間，就是系統當前時間 + 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"); // 5sheader("Cache-Control: no-cache"); //no cacheheader("Cache-Control: no-store"); //no cacheheader("Cache-Control: private"); //no cacheheader("Cache-Control: max-age=10"); //cache 10ssetcookie('hello',"testaaaa"); //no cache

注意session使用的時候有坑，可以用下面來設置

session_cache_limiter("none");session_start();echo date("Y-m-d H:i:s",time());

可以看一下PHP源代碼中的頭信息 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);}/* }}} *///再到這里3 或者上面幾個 ##默認是nocacheCACHE_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");}/* }}} *///這里2static 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);   //這里1            return 0;        }    }     return -1;}

三、清除緩存

NGINX只在商業版中支持proxy_cache_purge指令清除緩存，開源的ngx_cache_purge模塊只支持單一key的緩存清除。為了實現按目錄清除緩存只能自己開發。

NGINX作為Cache服務器時將資源內容以文件形式進行緩存，緩存元信息存儲于共享內存中，組織成一棵紅黑樹。紅黑樹中的每個節點代表一個Cache元信息。NGINX將Cache Key的HASH值作為紅黑樹節點的KEY。內容緩存文件以該HASH值作為文件名存儲在磁盤上。

NGINX的處理流程簡化描述是這樣的：當請求到達時，根據Cache Key的HASH值在紅黑樹中進行查找。如果找到，并查看相關信息，如果Cache可用，返回相應的Cache文件。否則，則回源抓取。

因為元信息是以Cache Key的HASH值作為Key存儲的，因而紅黑樹中并不能保留Cache Key中有層級關系. 如”/uri/foo”和”/uri/bar”在元信息紅黑樹中完全沒有關系。要實現按照目錄清除緩存，需要將Cache Key中層次關系存儲起來。

可以這樣做，在共享內存中建立一棵目錄樹來存儲層級關系。將Cache Key類比于文件系統中的路徑, 每級路徑存儲為樹中的一個節點。當需要清除某一目錄下的所有緩存時，將該節點子樹的中的所有緩存清除即可。

安裝Purge模塊

Purge模塊被用來清除緩存

wget http://labs.frickle.com/files/ngx_cache_purge-1.2.tar.gztar -zxvf ngx_cache_purge-1.2.tar.gz

編譯

./configure /…… /--with-http_geoip_module /--add-module=/usr/local/ngx_cache_purge-1.2

四、需要注意的一些問題

設置了之后重啟nginx就可以生效了，這個時候再訪問php的頁面的話，就會被緩存了，可以查看/var/logs/nginx/fastcgi_cache_dir這個目錄下面是有緩存文件的。最后再說明一點，如果更改了緩存目錄的路徑，一定要把緩存的名稱也改掉，后端調用的名稱也同步改掉，如果只改掉了緩存目錄，不改緩存名稱的話，緩存的時候還是會緩存到之前的路徑下面去，但是調用的時候調用的是新的路徑，這個時候就會出現找不到的情況

參考文章

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

上一篇：【nginx】常見的陷阱和錯誤

下一篇：【nginx】配置文件的優化