= ngx_http_upstream_memcached_hash_module =

Skip to the end for download.  Git repository: {{{ git clone git://openhack.ru/nginx-patched.git }}} branch ''memcached_hash''.

----

||'''syntax:''' memcached_hash [ketama_points=''points''] [weight_scale=''weight''][[BR]]'''default:''' none[[BR]]'''context:''' upstream||

||'''syntax:''' set $memcached_namespace ''"string"'';[[BR]]'''default:''' ""[[BR]]'''context:''' server, location, if||


This module implements ''memcached_hash'' directive for ''upstream'' blocks.  The purpose of this directive is to direct nginx to the right memcached server, the one that would be used by [http://openhack.ru/Cache-Memcached-Fast Cache::Memcached::Fast] (or its ancestor [http://search.cpan.org/dist/Cache-Memcached/ Cache::Memcached]) for the same key.  Thus you may upload
the data to memcached cluster with the Perl script using C::M::F (or in general with any client that is compatible with C::M), and then serve that data with nginx.

Parameters of ''memcached_hash'' directive:

ketama_points=''points'' - how many points the server has

weight_scale=''scale'' - denominator by which ketama points and server weights are scaled down. Thus, if you have ketama_points=150 and weight_scale=10 the server gets 150/10 = 15 points.

The typical configuration will be
{{{
server {
    location / {
        set             $memcached_key   "$uri$is_args$args";
        set             $memcached_namespace   "prefix";
        memcached_pass  memcached_cluster;
        error_page      404 502 504 = @fallback;
    }

    location @fallback {
        proxy_pass      http://backend;
    }
}
}}}
and ''memcached_cluster'' will be defined as
{{{
upstream memcached_cluster {
    memcached_hash;

    server localhost:11211 weight=2;
    server 192.168.254.2:11211;
    server unix:/path/to/unix.sock weight=4;
}
}}}
or
{{{
upstream memcached_cluster {
    memcached_hash ketama_points=150 weight_scale=10;

    server localhost:11211 weight=25;
    server 192.168.254.2:11211 weight=10;
    server unix:/path/to/unix.sock weight=40;
}
}}}
when corresponding parameters to Cache::Memcached::Fast are
{{{
my $memd = new Cache::Memcached::Fast({
    servers => [ { address => 'localhost:11211', weight => 2 },
                 '192.168.254.2:11211',
                 { address => '/path/to/unix.sock', weight => 4 } ],
    namespace => 'prefix',
    ...
});
}}}
or
{{{
my $memd = new Cache::Memcached::Fast({
    servers => [ { address => 'localhost:11211', weight => 2.5 },
                 '192.168.254.2:11211',
                 { address => '/path/to/unix.sock', weight => 4 } ],
    namespace => 'prefix',
    ketama_points => 150,
    ...
});
}}}
respectively.  See [http://git.openhack.ru/?p=nginx-patched.git;a=blob_plain;f=memcached_hash/README;hb=memcached_hash README] for further details.


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