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mod_memcache

About​

mod_memcache implements an API interface to memcached which is a "high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load."

This module can be used to distribute key/value pairs without having to resort to using ODBC and a database.

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Requirements​

mod_memcache requires one to have at least one memcached server running to be useful.

Installing​

To use mod_memcache:

Tell FreeSWITCH to compile in this module by editing modules.conf in the root of your freeswitch source tree and uncomment:

#applications/mod_memcache

Now go recompile FreeSWITCH.

make
make install

Tell FreeSWITCH to actually use the memcache module when running by adding the module to modules.conf.xml in /usr/local/freeswitch/conf/autoload_configs:

 <load module="mod_memcache"/>

Finally, edit the default config in the autoload_configs directory to hold your memcache connection information.

Now load up FreeSWITCH!

CLI​

From the commandline issue something similar to:

memcache status verbose

which would respond with something like:

Lib version: 0.27
Servers: 1
  localhost (11211)
    pid: 9542
    uptime: 25971
[...]

This verifies that you are actually communicating with your memcache servers.

Dialplan Application​

The memcache API can be called from the dialplan using the ${api(args)} method. Some examples:

<action application="set" data="foo=${memcache(get key)}"/>
<action application="set" data="ignore=${memcache(set key value)}"/>
<action application="set" data="ignore=${memcache(set key ${channel_var})}"/>

API​

The API can be called via ESL or used directly from fs_cli. There is pretty much a 1-1 relationship between the api below and the api exposed via libmemcached.

memcache <set|replace|add> <key> <value> [expiration [flags]]
  expiration is in seconds
  flags is a 64bit (preferably hex) value
memcache <get|getflags> <key>
  gets values or flags
memcache <delete> <key>
memcache <increment|decrement> <key> [offset [expires [flags]]]
  offset = how much to increase/decrease by
  expires = expiration in seconds -- subsequent inc/dec operations DO NOT extend lifetime of object
  flags = 64bit (preferably hex) value
memcache <flush>
  remove all keys (careful if this is a shared memcache server)
memcache <status> [verbose]
  retrieve server information

Sharing Data With Other Applications​

This is also very useful to share data across applications. Here an example how to share data between FreeSWITCH and a ruby memcache-client:

On Ruby/Rails set the namespace e.g. to "freeswitch" for the same memcached server in environment.rb

In FreeSWITCH add the following line to the dialplan:

 <action application="set" data="ignore=${memcache(set freeswitch:test 'This is a test')}"/>

Take care to prefix your key (here "test") with the Ruby namespace "freeswitch:".

Now you can receive the data in Ruby in raw mode:

 >> CACHE.get("test",0)
 => 'This is a test"

The 0 as second parameter is important for the raw mode, otherwise ruby will try to marshall the result from memcached and fails.