n4u
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pooler


			
				
					
						
						
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<title>pooler - An OTP Process Pool Application</title>
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<h1>pooler - An OTP Process Pool Application</h1>
<p>Copyright © 2011 Seth Falcon</p>
<p><b>Authors:</b> Seth Falcon (<a href="mailto:seth@userprimary.net"><tt>seth@userprimary.net</tt></a>).</p>
<p>
The pooler application allows you to manage pools of OTP behaviors
such as gen_servers, gen_fsms, or supervisors, and provide consumers
with exclusive access to pool members using pooler:take_member.</p>

<p>See the README.org file for a good introduction to what pooler is all
about.</p>

<h3><a name="Pooler_Configuration">Pooler Configuration</a></h3>

<p>Pool configuration is specified in the pooler application's
environment.  This can be provided in a config file using <code>-config</code> or
set at startup using <code>application:set_env(pooler, pools, Pools)</code>.
Here's an example config file that creates three pools of
Riak pb clients each talking to a different node in a local cluster:</p>

<pre>% pooler.config
% Start Erlang as: erl -config pooler
% -*- mode: erlang -*-
% pooler app config
[
 {pooler, [
         {pools, [
                  [{name, "rc8081"},
                   {max_count, 5},
                   {init_count, 2},
                   {start_mfa,
                    {riakc_pb_socket, start_link, ["localhost", 8081]}}],

                  [{name, "rc8082"},
                   {max_count, 5},
                   {init_count, 2},
                   {start_mfa,
                    {riakc_pb_socket, start_link, ["localhost", 8082]}}],

                  [{name, "rc8083"},
                   {max_count, 5},
                   {init_count, 2},
                   {start_mfa,
                    {riakc_pb_socket, start_link, ["localhost", 8083]}}]
                 ]}
        ]}
].</pre>

<h3><a name="Using_pooler">Using pooler</a></h3>

<p>Here's an example session:</p>

<pre>application:start(pooler).
P = pooler:take_member(),
% use P
pooler:return_member(P, ok).</pre>

<p>Once started, the main interaction you will have with pooler is through
two functions, <code>take_member/0</code> and <code>return_member/2</code>.</p>

Call <code>pooler:take_member()</code> to obtain a member from a randomly
selected pool.  When you are done with it, return it to the pool using
<code>pooler:return_member(Pid, ok)</code>.  If you encountered an error using
the member, you can pass <code>fail</code> as the second argument.  In this case,
pooler will permanently remove that member from the pool and start a
new member to replace it.  If your process is short lived, you can
omit the call to <code>return_member</code>.  In this case, pooler will detect
the normal exit of the consumer and reclaim the member.

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<p><i>Generated by EDoc, Apr 17 2011, 16:02:59.</i></p>
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