【nginx】關於fastcgi_cache，nginxfastcgi_cache

【nginx】關於fastcgi_cache，nginxfastcgi_cache
一、簡介

Nginx版本從0.7.48開始,支援了類似Squid的緩衝功能。這個緩衝是把URL及相關組合當做Key,用Md5演算法對Key進行雜湊，得到硬碟上對應的雜湊目錄路徑，從而將緩衝內容儲存在該目錄內。

Nginx Web 快取服務只能為指定URL或狀態代碼設定到期時間，不支援類似Squid的PURGE指令手動清除緩衝；但是我們可以通過Nginx的模組ngx_cache_purge清除指定URL的緩衝。

• proxy_cache：緩衝後端伺服器的內容，可能是任何內容，包括靜態和動態，減少了nginx與後端通訊的次數，節省了傳輸時間和後端寬頻
• fastcgi_cache：緩衝fastcgi產生的內容，很多情況是php產生的動態內容，少了nginx與php的通訊的次數，更減輕了php和資料庫(mysql)的壓力，這比用memcached之類的緩衝要輕鬆得多

圖片來自網路

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 $skip_cache 0;# POST requests and urls with a query string should always go to PHPif ($request_method = POST) {set $skip_cache 1;}   if ($query_string != "") {set $skip_cache 1;}   # Don't cache uris containing the following segmentsif ($request_uri ~* "/wp-admin/|/xmlrpc.php|wp-.*.php|/feed/|index.php|sitemap(_index)?.xml") {set $skip_cache 1;}   # Don't use the cache for logged in users or recent commentersif ($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  該指令用於設定哪個緩衝區將被使用，zone_name的值為fastcgi_cache_path指令建立的緩衝名稱

fastcgi_cache_path 範圍：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];

該指令用於設定快取檔案的存放路徑，樣本如下：fastcgi_cache_path /data/nginx/cache levels=1:2  keys_zone=cache_one:100M  inactive=1d  max_size=10g; 

a、levels:指定了該緩衝空間有兩層hash目錄，設定緩衝目錄層數，levels=1:2，表示建立兩層目錄緩衝，最多建立三層。第一層目錄名取fastcgi_cache_key md5的最後一個字元，第二層目錄名取倒數2-3字元，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為這個緩衝區起名為zone_name,500m指代緩衝空間為500MB; 

c、inactive=1d 代表如果快取檔案一天內沒有被訪問，則刪除; 

d、max_size=30g代表硬碟緩衝最大為30G;

設定緩衝多個磁碟

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;           }}

將快取檔案放入記憶體中

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緩衝是先寫在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之後可以在不同的分區，不過還是建議放同一分區

 

fastcgi_cache_methods 該指令用於設定緩衝哪些HTTP方法，預設緩衝HTTP GET/HEAD方法。 

fastcgi_cache_min_uses  URL經過多少次請求將被緩衝

fastcgi_cache_valid  reply_code [reply_code ... ] time

該指令用於對不同返回狀態代碼的URL設定不同的緩衝時間，例如：　

fastcgi_cache_valid 200 302 10m;fastcgi_cache_valid 404      1m;

設定202 302狀態URL緩衝10分鐘，404狀態的URL緩衝1分鐘。

注意：如果不指定狀態代碼，直接指定緩衝時間，則只有200,301,302狀態代碼會進行緩衝。

fastcgi_cache_valid 5m;

any 可以指定緩衝任何響應碼　　　　

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

緩衝的參數也可以在回應標頭直接設定。這些的優先順序高於緩衝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

該指令用來設定Web緩衝的Key值，Nginx根據Key值MD5緩衝。一般根據$host(網域名稱),$request_uri(請求的路徑)等變數組合成fastcgi_cache_key。

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

定義fastcgi_cache的key，樣本中就以請求的URI作為緩衝的key，Nginx會取這個key的md5作為快取檔案，如果設定了緩衝雜湊目錄，Nginx會從後往前取相應的位元做為目錄。

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後面的GET請求返回為空白

fastcgi_temp_path  path [level1 [level2 [level3]]];  預設為 fastcgi_temp;

該指令用來設定fastcgi_cache臨時檔案目錄

fastcgi_temp_path /spool/nginx/fastcgi_temp 1 2;

a temporary file might look like this:

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

fastcgi_cache_use_stale : fastcgi_cache_use_stale error | timeout | invalid_header | updating | http_500 | http_503 | http_403 | http_404 | off ...;

定義哪些情況下用到期緩衝

x-cache頭，用於調試

$upstream_response_time為到期時間

$upstream_cache_status 變數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 這裡需要特別注意

• Nginx fastcgi_cache在緩衝後端fastcgi響應時，當響應裡包含“set-cookie”時，不緩衝;
• 當回應標頭包含Expires時，如果到期時間大於當前伺服器時間，則nginx_cache會緩衝該響應，否則，則不緩衝;
• 當回應標頭包含Cache-Control時，如果Cache-Control參數值為no-cache、no-store、private中任意一個時，則不緩衝，如果Cache-Control參數值為max-age時，會被緩衝，且nginx設定的cache的到期時間，就是系統目前時間 + 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，可以用下面來設定

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

可以看一下PHP原始碼中的頭資訊 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);}/* }}} *///再到這裡3 或者上面幾個 ##預設是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");}/* }}} *///這裡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);   //這裡1            return 0;        }    }     return -1;}

三、清除緩衝

NGINX只在商業版中支援proxy_cache_purge指令清除緩衝，開源的ngx_cache_purge模組只支援單一key的緩衝清除。為了實現按目錄清除緩衝只能自己開發。

NGINX作為Cache伺服器時將資源內容以檔案形式進行緩衝，緩衝元資訊儲存於共用記憶體中，組織成一棵紅/黑樹狀結構。紅/黑樹狀結構中的每個節點代表一個Cache元資訊。NGINX將Cache Key的HASH值作為紅/黑樹狀結構節點的KEY。內容快取檔案以該HASH值作為檔案名稱儲存在磁碟上。

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/黑樹狀結構中進行尋找。如果找到，並查看相關資訊，如果Cache可用，返回相應的Cache檔案。否則，則回源抓取。

因為元資訊是以Cache Key的HASH值作為Key儲存的，因而紅/黑樹狀結構中並不能保留Cache Key中有層級關係. 如”/uri/foo”和”/uri/bar”在元資訊紅/黑樹狀結構中完全沒有關係。要實現按照目錄清除緩衝，需要將Cache Key中層次關係儲存起來。

可以這樣做，在共用記憶體中建立一棵分類樹來儲存層級關係。將Cache Key類比於檔案系統中的路徑, 每級路徑儲存為樹中的一個節點。當需要清除某一目錄下的所有緩衝時，將該節點子樹的中的所有緩衝清除即可。

安裝Purge模組

Purge模組被用來清除緩衝

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

設定了之後重啟nginx就可以生效了，這個時候再訪問php的頁面的話，就會被緩衝了，可以查看/var/logs/nginx/fastcgi_cache_dir這個目錄下面是有快取檔案的。最後再說明一點，如果更改了緩衝目錄的路徑，一定要把緩衝的名稱也改掉，後端調用的名稱也同步改掉，如果只改掉了緩衝目錄，不改緩衝名稱的話，緩衝的時候還是會緩衝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