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本文主要解析一下nginx ngx_http_proxy_module中的cache相关配置参数。
proxy_cache
| 名称 | 默认配置 | 作用域 | 官方说明 | 中文解读 | 模块 |
|---|---|---|---|---|---|
| proxy_cache | proxy_cache off; | http, server, location | Defines a shared memory zone used for caching. The same zone can be used in several places. Parameter value can contain variables (1.7.9). The off parameter disables caching inherited from the previous configuration level. | 设置是否开启对后端响应的缓存，如果开启的话，参数值就是zone的名称，比如proxy_cache mycache | ngx_http_proxy_module |
| proxy_cache_valid | 没有默认值，实例如proxy_cache_valid 200 302 10m; | http, server, location | Sets caching time for different response codes. | 针对不同的response code设定不同的缓存时间，如果不设置code，默认为200,301,302,也可以用any指定所有code | ngx_http_proxy_module |
| proxy_cache_key | proxy_cache_key $scheme$proxy_host$request_uri; | http, server, location | Defines a key for caching | 给缓存设定key，默认值相当于proxy_cache_key $scheme$proxy_host$uri$is_args$args; | ngx_http_proxy_module |
| proxy_cache_path | 没有默认值，实例proxy_cache_path /var/cache levels=1:2 keys_zone=imgcache:100m inactive=2h max_size=1g; | http | Sets the path and other parameters of a cache. Cache data are stored in files. The file name in a cache is a result of applying the MD5 function to the cache key. The levels parameter defines hierarchy levels of a cache: from 1 to 3, each level accepts values 1 or 2. | 指定缓存存储的路径，文件名为cache key的md5值，然后多级目录的话，根据level参数来生成，比如levels=1:2:3，第一个目录名取md5值的倒数第一个值，第二个目录名取md5值的第2和3个值，第三个目录名取md5值的第4，5，6个值；key_zone参数用来指定在共享内存中缓存的元数据的名称和内存大小，比如keys_zone=imgcache:100m，所有的缓存查找首先经过这里查找元数据，如果命中再去文件系统查找相应的缓存 ；inactive用来指定缓存没有被访问超时移除的时间，默认是10分钟，也可以自己指定比如inactive=2h ；max_size 用来指定缓存的最大值，超过这个值则会自动移除最近最少使用的缓存 | ngx_http_proxy_module |
| proxy_cache_bypass | 没有默认值 | http, server, location | Defines conditions under which the response will not be taken from a cache. If at least one value of the string parameters is not empty and is not equal to “0” then the response will not be taken from the cache. | 指定哪些响应在某些值不为空或不为0的情况下不走缓存，比如proxy_cache_bypass $http\_pragma $http_authorization; | ngx_http_proxy_module |
| proxy_cache_min_uses | proxy_cache_min_uses 1; | http, server, location | Sets the number of requests after which the response will be cached. | 指定在多少次请求之后才缓存响应内容 | ngx_http_proxy_module |
| proxy_cache_use_stale | proxy_cache_use_stale off; | http, server, location | Determines in which cases a stale cached response can be used during communication with the proxied server. The directive’s parameters match the parameters of the proxy_next_upstream directive. | 指定在后端服务器在返回什么状态码的情况下可以使用过期的缓存，比如proxy_cache_use_stale error timeout invalid_header http_500 http_502 http_503 http_504; | ngx_http_proxy_module |
| proxy_cache_lock | proxy_cache_lock off; | http, server, location | When enabled, only one request at a time will be allowed to populate a new cache element identified according to the proxy_cache_key directive by passing a request to a proxied server. Other requests of the same cache element will either wait for a response to appear in the cache or the cache lock for this element to be released, up to the time set by the proxy_cache_lock_timeout directive. | 默认不开启，开启的话则每次只能有一个请求更新相同的缓存，其他请求要么等待缓存有数据要么限时等待锁释放;nginx 1.1.12才开始有 | ngx_http_proxy_module |
| proxy_cache_lock_timeout | proxy_cache_lock_timeout 5s; | http, server, location | Sets a timeout for proxy_cache_lock. When the time expires, the request will be passed to the proxied server, however, the response will not be cached. | 等待缓存锁超时之后将直接请求后端，结果不会被缓存 ; nginx 1.1.12才开始有 | ngx_http_proxy_module |
实例
http {
# we set this to be on the same filesystem as proxy_cache_path
proxy_temp_path /usr/local/nginx/proxy_temp;
# good security practice dictates that this directory is owned by the
# same user as the user directive (under which the workers run)
proxy_cache_path /usr/local/nginx/proxy_temp keys_zone=CACHE:10m levels=1:2 inactive=6h max_size=1g;
server {
location / {
# using include to bring in a file with commonly-used settings
include proxy.conf;
# referencing the shared memory zone defined above
proxy_cache CACHE;
proxy_cache_valid any 1d;
proxy_cache_bypass $http_pragma $http_authorization;
proxy_cache_min_uses 3;
proxy_cache_use_stale error timeout invalid_header updating http_500 http_502 http_503 http_504;
proxy_pass http://upstream;
}
}
}