[erlang-patches] fix supervisors restarting temporary children

Henrik Nord <>
Tue Aug 23 09:48:05 CEST 2011

On 08/03/2011 05:07 PM, Frédéric Trottier-Hébert wrote:
> git fetch :ferd/otp.git fix_supervisor_temporary_restart
> This patch fixes the issue discussed at http://erlang.org/pipermail/erlang-questions/2011-August/060419.html, namely that in one_for_all or rest_for_one strategies, the supervisor is still trying to restart temporary children. Because we don't track their MFAs entirely, this causes repetitive crashes.
> This patch fixes the behaviour by inserting a clause in terminate_children/2-3 (private function) that will omit temporary children when building a list of killed processes, to avoid having the supervisor trying to restart them again.
> Only supervisors in need of restarting children used the list, so the change should be of no impact for the functions that called terminate_children/2-3 only to kill all children. This also avoids useless iterations if the filtering step were to be inserted at any other point in the code.
> A test suite has been added to supervisor_SUITE, containing checks for both one_for_all and rest_for_one. I've only ran the tests for the suite itself, but all of them pass without a problem.
> The commit/diff itself: https://github.com/ferd/otp/commit/25aab8efdef5c6898a679705158627cded3f847a
> --
> Fred Hébert
> http://www.erlang-solutions.com
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> http://erlang.org/mailman/listinfo/erlang-patches


Your patch has been reviewed, and we want you to fix the following for 
it to be graduated.

1) I think the test needs to be extended a bit. I can't see that it 
checks what happens to the temporary child - i.e. that it is terminated 
but not restarted. As far as I can understand it only checks that the 
supervisor survives...

2) There is a minor typo in the description of the test - it says 
one_for_rest instead of rest_for_one.

3) The behaviour must be documented - i.e. it must be explicitly stated 
that temporary children under one_for_all or rest_for_one supervisors 
will be terminated but not restarted.


Thank you.

/Henrik Nord Erlang/OTP

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