ensure_started

Bjorn Gustavsson <>
Thu Feb 27 10:48:14 CET 2003


"Vlad Dumitrescu (EAW)" <> writes:

> Hi,
> 
> I wonder about a thing. The following fun is an often used way to ensure that one uses "the one and only" server called ?MODULE.
> 
> ensure_started() ->
>     case whereis(?MODULE) of
> 	undefined ->
> 	    Pid = proc_lib:spawn(?MODULE, init, []),
> 	    register(?MODULE, Pid),
> 	    {ok, Pid};
> 	Pid ->
> 	    {ok, Pid}
>     end.
> 

A safer way is to move the call to register/2 into the init/0 function.

If two processes happens to start at almost the same time, the second
process will crash when calling register/2.

/Bjorn

-- 
Björn Gustavsson            Ericsson Utvecklings AB
      ÄT2/UAB/F/P
			    BOX 1505
+46 8 727 56 87 	    125 25 Älvsjö



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