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POHow to start multiple instances of the same module/function under the Supervisor behavior in erlang?
 

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  1. POHow to start multiple instances of the same module/function under the Supervisor behavior in erlang?
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    <p>Having a module/function <strong>mymodule</strong> , how to start it multiple times under the <a href="http://www.erlang.org/doc/man/supervisor.html#type-child_spec" rel="nofollow">supervisor</a> behavior ? </p> <p>I need for example 2 instances of the <strong>same process</strong> (mymodule) to be started concurrently. I called the children identifiers as <strong>child1</strong> and <strong>child2</strong>. They both point to the <strong>mymodule</strong> module that I want to start. I have specified two different functions to to start each instance of the worker process "mymodule" ( start_link1 and start_link2 )</p> <pre><code>-module(my_supervisor). -behaviour(supervisor). -export([start_link/0, init/1]). start_link() -&gt; supervisor:start_link({local, ?MODULE}, ?MODULE, _Arg = []). init([]) -&gt; {ok, {{one_for_one, 10, 10}, [{child1, {mymodule, start_link1, []}, permanent, 10000, worker, [mymodule]} , {child2, {mymodule, start_link2, []}, permanent, 10000, worker, [mymodule]} ]}}. </code></pre> <p>The <strong>worker</strong> has two distinguished start_link functions ( start_link1 and start_link2 ) for testing purposes:</p> <pre><code>-module(mymodule). -behaviour(gen_server). start_link1() -&gt; log_something("at link 1"), gen_server:start_link({global, child1}, ?MODULE, [], []). start_link2() -&gt; log_something("at link 2"), gen_server:start_link({global, child2}, ?MODULE, [], []). init([]) -&gt; .... </code></pre> <p>With the above I can see in my log the message "at link 1" but it does reveal "at link 2" anywhere. It also does not perform anything in the instance of link1 : just dies apparently. </p> <p>The only scenario that works is when the name "child1" <strong>matches</strong> the worker module name "mymodule". </p>
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    1. COIf you register the name of the process started with mymodule:start_link you will get this error as there can be only one process with the same registered name.
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