The ngx_http_memcached_module module allows to obtain responses from a memcached server. The key is set in the $memcached_key variable. A response should be put in memcached in advance via means that are external to nginx.

server {
    location / {
        set            $memcached_key "$uri?$args";
        memcached_pass host:11211;
        error_page     404 502 504 = @fallback;
    }

    location @fallback {
        proxy_pass     http://backend;
    }
}

memcached_buffer_size 4k|8k;

Sets size of the buffer used for reading a response received from the memcached server. A response is passed to a client synchronously, immediately as it is received.

memcached_connect_timeout 60s;

Defines a timeout for establishing a connection with the memcached server. It should be noted that this timeout cannot usually exceed 75 seconds.

memcached_next_upstream error timeout;

Specifies in which cases a request should be passed to the next server:

error

an error occurred while establishing a connection with the server, passing it a request, or reading the response header;

timeout

a timeout has occurred while establishing a connection with the server, passing it a request, or reading the response header;

invalid_response

a server returned empty or invalid response;

not_found

a response was not found on the server;

off

disables passing a request to the next server.

It should be understood that passing a request to the next server is only possible if a client was not sent anything yet. That is, if an error or a timeout occurs in the middle of transferring a response, fixing this is impossible.

Sets an address of the memcached server. An address can be specified as a domain name or an address, and a port, for example,

memcached_pass localhost:11211;

If a domain name resolves to several addresses, all of them will be used in a round-robin fashion. In addition, an address can be specified as a server group.

memcached_read_timeout 60s;

Defines a timeout for reading a response from the memcached server. A timeout is only set between two successive read operations, not for the transmission of the whole response. If a memcached server does not transmit anything within this time, a connection is closed.

memcached_send_timeout 60s;

Sets a timeout for transmitting a request to the memcached server. A timeout is only set between two successive write operations, not for the transmission of the whole request. If a memcached server does not receive anything within this time, a connection is closed.