How to do something when the server stop?

[Caiyun Deng]

Hi!

When i want to do something at the server start, I can do something in priv/init.

But when i want to do something at the server stop, How can i do?

[Jesse Gumm]

There's not currently (As far as I know) a standard way to do that,
but you could use a monitor to achieve it.

Ref = monitor(process, boss_sup),
receive
{'DOWN', _, process, {boss_sup, _}, _} -> run_my_other_shutdown_scripts()
end.

-Jesse

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Jesse Gumm
Owner, Sigma Star Systems
414.940.4866 || sigma-star.com || @jessegumm

[Caiyun Deng]

 Hi! I tried it,  I typed "q()" in ./init-dev.sh and "./init.sh stop" in the production mode, but it does not work.

 spawn(fun() -> monitor_stop() end),

monitor_stop() ->

    ?TRACE_VAR(monitor_stop),

    Ref = erlang:monitor(process, boss_sup),

    receive

        Msg ->

            ?TRACE_VAR(Msg),

            monitor_stop()

    end.

在 2014年8月6日星期三UTC+8上午3时02分11秒，Jesse Gumm写道：

[chan sisowath]

hi,

same as init

just implement stop/1 in you module piv/init

if it doesn't work just make an issue.

chan

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[Caiyun Deng]

I also tried stop/1 in priv/init, it does not work.

But it didn't say the stop/1 will execute when the server stop. It just say that "stop is executed if the script is ever reloaded".

在 2014年8月6日星期三UTC+8下午1时38分06秒，mihawk写道：

[chan sisowath]

it is called when reloaded:
here https://github.com/ChicagoBoss/ChicagoBoss/blob/master/src/boss/boss_web_controller.erl#L131

but it is called also when boss_web_controller terminate:

https://github.com/ChicagoBoss/ChicagoBoss/blob/master/src/boss/boss_web_controller.erl#L32

as far as i know

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[Caiyun Deng]

Does your stop/1 in the priv/init will be called when the server stop?

在 2014年8月6日星期三UTC+8下午2时40分52秒，mihawk写道：

[chan sisowath]

this code should work :).

as jesse suggested

-module(test_script).

-export([init/0, stop/1]).
-export([watch_boss/0]).


init() ->
    Pid = spawn(?MODULE, watch_boss, []),
    io:format("~n~n<<<< -------- init -------- script --------->> Pid ~p ~n~n",[Pid]),
    {ok, []}.

stop(_) ->
 [].

watch_boss() ->
    Ref = monitor(process, boss_web),
    receive
        {Reason, _, process, {boss_web, _}, _} ->
            %% call my awesome script
            io:format("~n~n<<<< -------- stop -------- script --------->> ~p ~p<<---~n~n",[Ref, Reason])
    end.

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[Jesse Gumm]

I'm honestly not sure how gracefully q() kills the VM, but both Chan and I are giving suggestions for when you run boss:stop().

If you are going want to shut down gracefully, then I'd suggest boss:stop(), followed by q().

Then you can be sure your shutdown scripts have been run. That said, there are obviously numerous reasons a VM could be shut down instantly and without a proper shutdown (kill -9, power failure, kernel panic, etc).

If you can, I recommend building around that kind of restriction, rather than relying on a "clean shutdown" every time.

--
Jesse Gumm
Owner, Sigma Star Systems
414.940.4866 || sigma-star.com || @jessegumm

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[Caiyun Deng]

monitor(process, boss_web)

It works.

Thanks for your help!