[erlang-questions] simple_one_for_one supervisor - what happens at restart? (also: gen_tcp)

Ryan Stewart <>
Sun May 22 01:25:03 CEST 2016


I think you're still ignoring the ordering guarantees of supervision. If
"top_sup" supervises [important_server_process, "worker_sup"], and
"worker_sup" is a simple_one_for_one where you keep your
transient/temporary workers, then "top_sup" will ensure that
important_server_process doesn't get the shutdown signal until all workers
are finished. It may not apply in this specific case, but I've found it
invaluable.

On Tue, May 17, 2016 at 3:09 PM Chandru <
> wrote:

> On 17 May 2016 at 00:49, Fred Hebert <> wrote:
>
>> On 05/16, Chandru wrote:
>>
>>>
>>> No, it's not. The reason a terminate callback is provided in a gen_server
>>> is so that a process can clean up when it terminates, not to delegate it
>>> to
>>> other processes.
>>>
>>>
>> I'm gonna side with Loďc here. The terminate callback is good for any
>> process-local cleanup or optimistic work, but is by no means a safe way to
>> terminate anything.
>
>
>>
>> For example, if you have many children to terminate and through some
>> interleaving brutall_kill is triggered (or anyone calls exit(Pid, kill)),
>> whatever work you wanted to do in terminate will be skipped by a
>> non-trappable exit signal.
>>
>
> Agreed, but how does adding the connection handling process (in Oliver's
> use case) to a simple_one_for_one supervisor help? It doesn't give him
> anything other than the illusion of being "supervised".
>
> Chandru
>
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