proxy_cache_min_uses 3;
proxy_cache_bypass $cookie_nocache $arg_nocache;

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proxy_cache_min_uses 3; #3次查询之后结果会缓存
proxy_cache_bypass $cookie_nocache $arg_nocache;

cookie_nocache和arg_nocache这两个变量不为空时该次请求结果不从缓存中取出

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http://nginx.org/cn/docs/http/ngx_http_proxy_module.html