[erlang-patches] allow use of proplists in supervisor start specs

[Siri Hansen]

I have pushed the current status of this job to github. Comments still
welcome!
/siri

https://github.com/sirihansen/otp/compare/erlang:980d7fa32128d43d36fb9527df1967eff801be9c...siri/sup-spec-maps/OTP-11043


2014-07-03 20:24 GMT+02:00 DeadZen <deadzen@REDACTED>:

> +1 on the latest revision
>
> On Thu, Jul 3, 2014 at 9:57 AM, Siri Hansen <erlangsiri@REDACTED> wrote:
> > Hello,
> >
> > thanks for the feedback! We have decided to take your comments into
> account
> > and change the default values as follows:
> >
> > Intensity/Perior: 1/5
> > Shutdown for worker: 5000
> > Shutdown for supervisor: infinity
> >
> > The reasoning behind it is that
> >
> > 1. as a few of you commented, it is probably not a good idea to have a
> > default without restarts, as restarts is a very important property of the
> > supervisor tree. Using 1 restart in 5 seconds was a compromise between my
> > first intention of "being extreme" and the suggestions from the list...
> And
> > also - if a process can not be restarted on the first attempt, then
> maybe it
> > is not so great a chance that it will succeed on the second attempt
> either.
> > And 5 seconds is a very good number!!
> >
> > 2. to avoid the confusion of why the terminate function is not executed,
> we
> > decided not to use 'brutal_kill'. Which number to use is probably not
> that
> > important, so we chose 5000 - which we all know is proven to be "the best
> > timeout value" ;)
> >
> > 3. the recommended shutdown value for supervisors is 'infinity', and I
> think
> > that should be reflected in the default. Having the same (integer) value
> as
> > for workers can give very strange results.
> >
> > Further comments are still welcome... :)
> >
> > /siri
> >
> >
> >
> >
> >
> >
> >
> > 2014-07-01 14:43 GMT+02:00 Daniel Luna <daniel@REDACTED>:
> >
> >> I have to mention that I think brutal_kill is a really bad choice for a
> >> default.
> >>
> >> It breaks the expectation in Erlang that supervisors can never crash. An
> >> expectation that is in the core of what makes Erlang the great language
> that
> >> it is.
> >>
> >> Dangling process trees are not fun to deal with (and don't happen on a
> VM
> >> crash).
> >>
> >> To preserve the correctness and trust of supervision trees the default
> >> should be either infinity or depend on the child type.
> >>
> >> For worker children brutal_kill is fine. For supervisor children
> infinity
> >> is the only sensible choice.
> >>
> >> On Jul 1, 2014 7:06 AM, "Loïc Hoguin" <essen@REDACTED> wrote:
> >>>
> >>> Just wanted to say I agree with everything José said, except 3. the
> >>> different defaults for different process types. It makes things too
> hard to
> >>> keep track of.
> >>>
> >>> I think brutal_kill is a great choice because it makes it easier for
> the
> >>> user to stumble upon cold-start issues when restarting their
> >>> application/release. The VM may crash so there's never a guarantee to
> run
> >>> shutdown functions anyway, and too few people forget to test cases when
> >>> these didn't run, leading to potential production disasters.
> >>>
> >>> On 06/30/2014 04:37 PM, José Valim wrote:
> >>>>
> >>>> I have some feedback based on my experience in writing and teaching
> >>>> Erlang/Elixir.
> >>>>
> >>>> 1. I would always require the supervision strategy. When I am
> >>>> prototyping, it is usually hard for me to reason about the intensity
> and
> >>>> restarts, but I can always reason about the supervision strategy. All
> >>>> teaching materials I know of also discuss the supervision right away,
> so
> >>>> having it explicit shouldn't hurt those cases.
> >>>>
> >>>> For such cases, maybe we should use the format of {{strategy(),
> map()},
> >>>> [children()]} (which is similar to what we have today).
> >>>>
> >>>> 2. I also agree with Richard. Having a default of 0 restarts may cause
> >>>> confusion and forcing people to define them won't help when they still
> >>>> have no idea of what values they should use (because it is
> prototyping /
> >>>> early deploys). I usually fine tune those values based on the
> production
> >>>> system reports so having saner defaults, like Ulf's, may make more
> >>>> sense.
> >>>>
> >>>> 3. The child_spec defaults are great and similar to the ones we use in
> >>>> Elixir with the only difference being the shutdown value. We have a
> >>>> default of 5000, which is the one usually recommended, but we set it
> to
> >>>> "infinity" if the type is a "supervisor" (which is the OTP docs
> >>>> recommendation if I remember correctly).
> >>>>
> >>>> Regarding 3., if the recommendation and the consensus in actual
> systems
> >>>> is to use brutal_kill for shutdown, I will gladly change Elixir to
> make
> >>>> it consistent with OTP defaults.
> >>>>
> >>>> Thanks for opening the changes for discussion!
> >>>>
> >>>> *José Valim*
> >>>> www.plataformatec.com.br <http://www.plataformatec.com.br/>
> >>>> Skype: jv.ptec
> >>>> Founder and Lead Developer
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> erlang-patches mailing list
> >>>> erlang-patches@REDACTED
> >>>> http://erlang.org/mailman/listinfo/erlang-patches
> >>>>
> >>>
> >>> --
> >>> Loïc Hoguin
> >>> http://ninenines.eu
> >>> _______________________________________________
> >>> erlang-patches mailing list
> >>> erlang-patches@REDACTED
> >>> http://erlang.org/mailman/listinfo/erlang-patches
> >
> >
> >
> > _______________________________________________
> > erlang-patches mailing list
> > erlang-patches@REDACTED
> > http://erlang.org/mailman/listinfo/erlang-patches
> >
>
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