fastcgi_cache

Posted 2020-10-11 小龙

tags:

篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了fastcgi_cache相关的知识，希望对你有一定的参考价值。

技术分享

流程：

用户第一次请求，会把返回的文件同时缓存起来，如果再有请求，命中缓存直接从cache返回数据，省去了fastcgi和php通信处理过程

原理：

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（URL 以及相关组合）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。

缓存过程：两个Nginx 进程参与缓存，cache loader 和 cache manager。cache manager 定期激活检查缓存文件存在器的状态。特别地，当文件存储器的大小超过 max_size 参数的值时，把最近最少使用到的数据删除。cache loader 只激活一次，在Nginx启动之后。它加载先前缓存的数据的元信息到共享内存区。一次性在头一分钟内加载所有的缓存可能会消耗大量的资源和减慢 Nginx 的性能。

fastcgi_cache_path /data/service_data/cache levels=1:2 keys_zone=DOMAIN_CACHE:100m max_size=300m inactive=1h;
add_header X-Cache "$upstream_cache_status";
server {
  
    set $hosttype  "web";
    set $tag  0;
    set $cache 1;
    if ( $request_uri ~ ^([^\?]*)(\?.*)?){
       set $key $1;
    }
  
    if ( $http_user_agent ~* ‘(iPhone|iPod|Opera Mini|android.*Mobile|NetFront|PSP|BlackBerry|Windows Phone)‘ ) {
            set $tag  "${tag}1" ;
    }
    if ( $key ~*  ^/((www/fyc(/)?)|(index(/)?)|(index.php)?)$ ){
            set $tag  "${tag}2";
    }
  
    if ( $tag = "012" ) {
            set $cache  0;
            set $hosttype  "wap";
    }
  
    if ( $key ~*  ^/www/fyc/brifinfo/ ) {
            set $tag  "${tag}3";
    }
  if ( $http_user_agent ~* ‘(Guazi/newcar|Guazi/c)‘) {
             set $tag  "${tag}4";
  }
  
    if ( $tag = "013" ) {
            set $cache  0;
            set $hosttype  "wap";
    }
  
    if ( $tag = "02" ){
            set $cache 0;
    }
   
    if ( $tag = "03" ){
             set $cache 0;
    }
    if ( $tag = "024"){
         set $cache 0;
         set $hosttype  "app";
   }
   if ( $tag = "034" ){
         set $cache 0;
         set $hosttype  "app";
   }
    
    if ( $tag = "0124"){
             set $cache 0;
             set $hosttype  "app";
    }
    if ( $tag = "0134" ){
            set $cache 0;
            set $hosttype  "app";
    }
  ocation ~* .*\.php?$
    {
        //接口层面
        set $cache  1;  
        if ( $http_fpmcache = 1 ){
            set $cache  0;     //如何header 传fpmcache 1 代表使用缓存
        }
        fastcgi_cache_key $scheme$host$request_uri$request_method;//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_cache DOMAIN_CACHE;
        fastcgi_cache_valid 200 302 301 10m;
        fastcgi_cache_use_stale updating error timeout invalid_header http_500 http_503 http_404;
        fastcgi_ignore_headers Cache-Control Expires Set-Cookie;
        fastcgi_cache_bypass $cookie_nocache;
        fastcgi_no_cache  $cache;
        add_header X-Cache $upstream_cache_status;
        add_header X-URI   $key|$request_method|$hosttype|$tag|$cache;
 
......
        }
}

关注状态点：

$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 cach

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
解决：
加上fastcgi_ignore_headers Cache-Control Expires Set-Cookie;可以解决这个问题

性能对比：

四核逻辑cpu

4G 内存

使用Jmeter 压测

10.16.208.86 (g1-nc-test-v02)

	g1-nc-test-v02
线程/sec	tps	接口平均响应	cpu
100	270/sec	253ms	60%-70%
150	240/sec	494ms	70%-84%
200	281/sec	561ms	84%左右
300	280/sec	901ms	84%左右
500	264/sec	1481ms	84%左右

使用了fastcgi_cache

四核逻辑cpu

4G 内存

使用Jmeter 压测

10.16.208.87 (g1-nc-test-v01)

	g1-nc-test-v01
线程/sec	tps	接口平均响应	cpu
100	832/sec	27ms	5%下
150	1067/sec	39ms	5%下
200	1294/sec	64ms	5%下
300	1107/sec	153ms	5%下
500	955/sec	284ms	5%下

以上对比结果：使用了fastcgi_cache 对QPS 有大概3-5倍的提升速度。（本地单机实测，使用是未使用的10倍左右）。

缓存命中率
遗憾没有相关命令去查看或者统计缓存命中率，只能通过把$upstream_cache_status 打到日志上统计了。

目前测试命中率大概处于88%-98%之间

//类似shell脚步统计
if [ "$1" != ‘‘ ];then
    if [ -e "$1" ];then
        HIT=`cat $1 | grep HIT | wc -l`
        ALL=`cat $1 | wc -l`
        HIT_RATE=`echo "scale=2;($HIT/$ALL)*100" | bc`
        echo "HIT_rate = $HIT_RATE"
    else
        echo "$1 xxxxxx"
    fi
else
     xxxxx
fi
  