[erlang-questions] Is supervisor notified when child is restarted?

[Sean Cribbs]

Hi Martin,

It sounds like you need either to use either registered names, process
groups, or the one_for_all strategy. Registered processes are the easiest
way, you can simply refer to them by the atom -- but you must expect that
sometimes messages will be lost if the process is restarting. Alternately,
if you change this supervisor's strategy to one_for_all you will ensure
that every process always has the correct state (assuming it already starts
up in the correct state), but existing work from non-failed processes can
be lost. For process groups, you can use pg2 [1] which comes with OTP, or
there are several alternate implementations available on github, but
messaging the other processes in this small group will incur additional
overhead.

Each solution has tradeoffs, I hope that helps you decide which one to use.

On Tue, Jul 28, 2015 at 10:03 AM, Martin Koroudjiev <mrtndimitrov@REDACTED>
wrote:

> Hello,
>
> I am wondering how can I get notified when a child process is restarted?
> Imagine this simple scenario - supervisor with one_for_one strategy and
> 3 gen_servers as workers. Each in its state has the PIDs of the other 2
> and sends them messages. Now if one child gets restarted, the other 2
> will have the old PID. How can I notify them?
>
> I can't restart the whole supervision tree because the number of child
> processes is buried deep in the initialization logic of the application.
>
> Regards,
> Martin
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