time it takes to reastart gen_server

[Gunilla Arendt]

You don't have a gen_server, you have a plain Erlang process.
The process calls "gen_server:call(self(), stop)" when the port
is closed, thus sending a gen_server request to itself. But since
the process is not a gen_server (and does not handle the request),
no reply is received and the function call does not return until
the default gen_server timeout expires (incidentally, after 5 seconds)
and only then does the process terminate.

Instead of calling "gen_server:call(self(), stop)", simply let
the process terminate by -- for example -- returning an atom 'stop':

...
     receive
         {'EXIT',Port,Reason} ->
             io:format(...),
             stop;
...

Also, I recommend you read "Design Principles" in the Erlang/OTP
documentation to learn more about generic servers.

/ Gunilla


Dietmar Schaefer wrote:
> Happy new year !
> 
> 
> I am trying to develop a gen_server which starts a unix process
> 
> 
> do(ExtPrg) ->    process_flag(trap_exit, 
> true),                           %% to get informed when process terminates
>    Port = open_port({spawn, ExtPrg}, [{packet, 2}]),        %% ExtProg 
> also includes parameter
>    loop(Port).
> 
> 
> 
> loop(Port) ->
>    receive
>    {'EXIT',Port,Reason}   ->   io:format("external program exited~n 
> Reason=~p Port=~p~n",[Reason,Port]),    %port program died
>                    gen_server:call(self(),stop)   %% all work is done - 
> go home
>    end.
> 
> 
> 
>   This gen_server is supervised by a  supervisor.
> 
> init(_Args) ->      case  whereis(watchdog) of
>    undefined ->                    %% register only once
>     register(watchdog, self());
>    _ -> ok
>    end,
> 
> 
> Xclock = {xclock,{xclock,start_link,["/usr/X11R6/bin/xclock"]},
>      permanent,brutal_kill,worker,[xclock]},
> 
> Xterm =  {xterm,{xterm,start_link,["/usr/bin/xterm"]},
>       permanent,brutal_kill,worker,[xterm]},
> 
>    {ok,{{one_for_one,1,6}, [Xclock,Xterm]}}.
> 
> 
> It takes 5 seconds to restart my xclock after I closed it.
> 
> How can I fasten it up ?
> 
> regards
> 
> 
> Dietmar
> 
>