<?xml version="1.0"?>

<!--
  Copyright (C) Igor Sysoev
  Copyright (C) Nginx, Inc.
  -->

<!DOCTYPE module SYSTEM "../../../../dtd/module.dtd">

<module name="Module ngx_http_memcached_module"
        link="/en/docs/http/ngx_http_memcached_module.html"
        lang="en"
        rev="7">

<section id="summary">

<para>
The <literal>ngx_http_memcached_module</literal> module is used to obtain
responses from a memcached server.
The key is set in the <var>$memcached_key</var> variable.
A response should be put in memcached in advance by means
external to nginx.
</para>

</section>


<section id="example" name="Example Configuration">

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

    location @fallback {
        proxy_pass     http://backend;
    }
}
</example>
</para>

</section>


<section id="directives" name="Directives">

<directive name="memcached_bind">
<syntax><value>address</value> | <literal>off</literal></syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>0.8.22</appeared-in>

<para>
Makes outgoing connections to a memcached server originate
from the specified local IP <value>address</value>.
Parameter value can contain variables (1.3.12).
The special value <literal>off</literal> (1.3.12) cancels the effect
of the <literal>memcached_bind</literal> directive
inherited from the previous configuration level, which allows the
system to auto-assign the local IP address.
</para>

</directive>


<directive name="memcached_buffer_size">
<syntax><value>size</value></syntax>
<default>4k|8k</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Sets the <value>size</value> of the buffer used for reading the response
received from the memcached server.
The response is passed to the client synchronously, as soon as it is received.
</para>

</directive>


<directive name="memcached_connect_timeout">
<syntax><value>time</value></syntax>
<default>60s</default>
<context>http</context>
<context>server</context>
<context>location</context>

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

</directive>


<directive name="memcached_gzip_flag">
<syntax><value>flag</value></syntax>
<default></default>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>1.3.6</appeared-in>

<para>
Enables the test for the <value>flag</value> presence in the memcached
server response and sets the “<literal>Content-Encoding</literal>”
response header field to “<literal>gzip</literal>”
if the flag is set.
</para>

</directive>


<directive name="memcached_next_upstream">
<syntax>
    <literal>error</literal> |
    <literal>timeout</literal> |
    <literal>invalid_response</literal> |
    <literal>not_found</literal> |
    <literal>off</literal>
    ...</syntax>
<default>error timeout</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Specifies in which cases a request should be passed to the next server:
<list type="tag">

<tag-name><literal>error</literal></tag-name>
<tag-desc>an error occurred while establishing a connection with the
server, passing a request to it, or reading the response header;</tag-desc>

<tag-name><literal>timeout</literal></tag-name>
<tag-desc>a timeout has occurred while establishing a connection with the
server, passing a request to it, or reading the response header;</tag-desc>

<tag-name><literal>invalid_response</literal></tag-name>
<tag-desc>a server returned an empty or invalid response;</tag-desc>

<tag-name><literal>not_found</literal></tag-name>
<tag-desc>a response was not found on the server;</tag-desc>

<tag-name><literal>off</literal></tag-name>
<tag-desc>disables passing a request to the next server.</tag-desc>

</list>
</para>

<para>
One should bear in mind that passing a request to the next server is
only possible if nothing has been sent to a client yet.
That is, if an error or timeout occurs in the middle of the
transferring of a response, fixing this is impossible.
</para>

<para>
The directive also defines what is considered an unsuccessful attempt
of communication with a
<link doc="ngx_http_upstream_module.xml" id="server"/>.
The cases of <literal>error</literal>, <literal>timeout</literal> and
<literal>invalid_header</literal> are always considered unsuccessful attempts,
even if they are not specified in the directive.
The case of <literal>not_found</literal>
is never considered an unsuccessful attempt.
</para>

</directive>


<directive name="memcached_pass">
<syntax><value>address</value></syntax>
<default/>
<context>location</context>
<context>if in location</context>

<para>
Sets the memcached server address.
The address can be specified as a domain name or an address, and a port:
<example>
memcached_pass localhost:11211;
</example>
or as a UNIX-domain socket path:
<example>
memcached_pass unix:/tmp/memcached.socket;
</example>
</para>

<para>
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
<link doc="ngx_http_upstream_module.xml">server group</link>.
</para>

</directive>


<directive name="memcached_read_timeout">
<syntax><value>time</value></syntax>
<default>60s</default>
<context>http</context>
<context>server</context>
<context>location</context>

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

</directive>


<directive name="memcached_send_timeout">
<syntax><value>time</value></syntax>
<default>60s</default>
<context>http</context>
<context>server</context>
<context>location</context>

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

</directive>

</section>


<section id="variables" name="Embedded Variables">

<para>
<list type="tag">

<tag-name id="var_memcached_key"><var>$memcached_key</var></tag-name>
<tag-desc>
Defines a key for obtaining response from a memcached server.
</tag-desc>

</list>
</para>

</section>

</module>