Here's my (unimportant and unsolicited ^_^) opinion. I think this should be left as is for a couple of reasons. 1. In the case you mentioned where a file is opened in the c'tor, the file could have been opened during preStart. That way if you allocate the resource, you will get to postStop, and if you fail in preStart you haven't allocated resources (or you know how far along the initialization you are so you can clean up the resources that were actually allocated). 2. I generally think of preStart and postStop as being associated, like a constructor and destructor (in languages that have them). In such cases, if the constructor fails the destructor isn't called, and I think this case is similar. 3. And finally, of course, there's the backwards-compatibility issue that was already mentioned here. I doubt it'll cause many issues, but the ones it will cause will probably be fairly hard to detect (most projects don't have tests for every object failing initialization).
Tal On Thursday, March 31, 2016 at 3:50:00 PM UTC+3, drewhk wrote: > > That is an orthogonal concern in my eyes. The following options are > possible now > - init fails > - init; preStart fails > - init; preStart; postStop (fails)? > > The above contract is basically: "If any initialization fails, postStop is > never called" > > It can be changed to > - init fails > - init; preStart (fails)?; postStop (fails)? > > The above contract is basically: "If initialization succeeds, preStart and > postStop are attempted to be called eventually, independently of thrown > exceptions" > > I proposed the second as it makes postStop a new line of defense which it > hasn't been before. For example stream stages *do* attempt to call postStop > even if preStart throws. > > -Endre > > > > On Thu, Mar 31, 2016 at 2:41 PM, Viktor Klang <[email protected] > <javascript:>> wrote: > >> PostStop would never be called if the constructor fails. Which could be >> said to be similar to preStart? >> >> -- >> Cheers, >> √ >> On Mar 31, 2016 2:39 PM, "Endre Varga" <[email protected] >> <javascript:>> wrote: >> >>> >>> >>> On Thu, Mar 31, 2016 at 2:36 PM, Guido Medina <[email protected] >>> <javascript:>> wrote: >>> >>>> it gets worse if I failed starting "b" because now "a" is started and >>>> it won't be stopped, >>>> >>> >>> I don't understand this question. If we failed starting "b" then it will >>> not be running, this is not changed by calling postStop() on the retreat >>> before nulling out the actor. >>> >>> >>>> such cases IMHO should be handled by the user >>>> >>> and >>>> instead just stick to the contract which is, "stop if was started" >>>> which will lead to less >>>> >>> >>> The contract will be here just as simple first preStart and eventually >>> postStop will be attempted to be called, after which the actor is GC-able. >>> This is also a simple contract. >>> >>> >>>> confusion and easier to maintain the exceptional cases. >>>> >>>> >>>> On Thursday, March 31, 2016 at 1:23:39 PM UTC+1, Guido Medina wrote: >>>>> >>>>> so, say: >>>>> >>>>> Object a = null, Object b = null; >>>>> >>>>> preStart(): >>>>> >>>>> a = new something(); a.start(); *<= say I failed here.* >>>>> b = new somethingElse(); b start(); >>>>> >>>>> postStop(): >>>>> >>>>> b.stop(); boom NPE. >>>>> a.stop(); >>>>> >>>>> That's why the word transaction exist right? A unit is considered >>>>> started or valid of all its parts are valid and started... >>>>> But go ahead, make legacy code life miserable...the decision is yours. >>>>> >>>>> Try catch is there for a reason but somehow magic exists. >>>>> >>>>> Guido. >>>>> >>>>> On Thursday, March 31, 2016 at 1:15:27 PM UTC+1, drewhk wrote: >>>>>> >>>>>> >>>>>> >>>>>> On Thu, Mar 31, 2016 at 2:10 PM, Guido Medina <[email protected]> >>>>>> wrote: >>>>>> >>>>>>> I haven't seen any system stopping something consciously that it was >>>>>>> unable to start, the created instance is just an instance like another >>>>>>> other object which will be GCed. >>>>>>> >>>>>> >>>>>> I don't agree, you might have opened a file or socket in the >>>>>> constructor or parts of preStart() before the exception. >>>>>> >>>>>> >>>>>>> If you look at it from a state machine perspective Status: CREATED >>>>>>> => CALL START (or preStart don't worry about details) => Status: Started >>>>>>> >>>>>>> It is more destructive to call postStop if it didn't actually >>>>>>> started because then you will get NPE for stopping things that are part >>>>>>> of >>>>>>> the actor that weren't instantiated. >>>>>>> >>>>>> Now I have to protect my code from Akka calling postStop...see my >>>>>>> point? >>>>>>> >>>>>> >>>>>> Nope, Akka should just swallow the double-fault at that point. I >>>>>> still think it should at least attempt to call postStop() to mitigate >>>>>> resource leaks. >>>>>> >>>>>> -Endre >>>>>> >>>>>> >>>>>>> >>>>>>> Guido. >>>>>>> >>>>>>> On Thursday, March 31, 2016 at 9:19:15 AM UTC+1, drewhk wrote: >>>>>>>> >>>>>>>> That description suits me ;) >>>>>>>> >>>>>>>> On Thu, Mar 31, 2016 at 10:18 AM, Patrik Nordwall < >>>>>>>> [email protected]> wrote: >>>>>>>> >>>>>>>>> From the source: "Only change this if you're very confident and >>>>>>>>> lucky" :-) >>>>>>>>> >>>>>>>>> On Thu, Mar 31, 2016 at 9:30 AM, Endre Varga < >>>>>>>>> [email protected]> wrote: >>>>>>>>> >>>>>>>>>> Shouldn't we all postStop there if preStart has been at least >>>>>>>>>> invoked (i.e. there is already an instance)? It does not seem to be >>>>>>>>>> hard, >>>>>>>>>> just shuffling that code a bit around (famous last words?). >>>>>>>>>> >>>>>>>>>> On Thu, Mar 31, 2016 at 9:25 AM, Patrik Nordwall < >>>>>>>>>> [email protected]> wrote: >>>>>>>>>> >>>>>>>>>>> I think that is how it is implemented. Exception from preStart >>>>>>>>>>> results in clearing the actor field and >>>>>>>>>>> throwing ActorInitializationException: >>>>>>>>>>> >>>>>>>>>>> https://github.com/akka/akka/blob/master/akka-actor/src/main/scala/akka/actor/ActorCell.scala#L599 >>>>>>>>>>> >>>>>>>>>>> Default supervision will result in stop, but postStop is not >>>>>>>>>>> called because the actor field was cleared: >>>>>>>>>>> https://github.com/akka/akka/blob/master/akka-actor/src/main/scala/akka/actor/dungeon/FaultHandling.scala#L210 >>>>>>>>>>> >>>>>>>>>>> On Wed, Mar 30, 2016 at 10:59 AM, Endre Varga < >>>>>>>>>>> [email protected]> wrote: >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> On Sun, Mar 27, 2016 at 5:52 PM, Stanislav Savulchik < >>>>>>>>>>>> [email protected]> wrote: >>>>>>>>>>>> >>>>>>>>>>>>> Hi, everyone! >>>>>>>>>>>>> >>>>>>>>>>>>> I've discovered that Actor's postStop method doesn't get >>>>>>>>>>>>> invoked if exception occurs during actor initialization via >>>>>>>>>>>>> preStart >>>>>>>>>>>>> method. Does anyone know if it is the correct behavior? I >>>>>>>>>>>>> expected that the >>>>>>>>>>>>> failed actor could close some resources in postStop. >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Do you have a reproducer for this? I would also expect postStop >>>>>>>>>>>> to be at least attempted to be called. >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> P.S. The behavior differs when a failure occurs during regular >>>>>>>>>>>>> vs. system message processing and supervisor decides to Stop the >>>>>>>>>>>>> failed >>>>>>>>>>>>> child. It seems inconsistent to me. >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> What do you mean here? Can you provide a small example to show >>>>>>>>>>>> this? >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> -- >>>>>>>>>>>>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>>>>> >>>>>>>>>> Check the FAQ: >>>>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>>>>>> >>>>>>>>>> Search the archives: >>>>>>>>>>>>> https://groups.google.com/group/akka-user >>>>>>>>>>>>> --- >>>>>>>>>>>>> You received this message because you are subscribed to the >>>>>>>>>>>>> Google Groups "Akka User List" group. >>>>>>>>>>>>> To unsubscribe from this group and stop receiving emails from >>>>>>>>>>>>> it, send an email to [email protected]. >>>>>>>>>>>>> To post to this group, send email to [email protected]. >>>>>>>>>>>>> Visit this group at https://groups.google.com/group/akka-user. >>>>>>>>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> -- >>>>>>>>>>>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>>>> >>>>>>>>>> Check the FAQ: >>>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>>>>> >>>>>>>>>> Search the archives: >>>>>>>>>>>> https://groups.google.com/group/akka-user >>>>>>>>>>>> --- >>>>>>>>>>>> You received this message because you are subscribed to the >>>>>>>>>>>> Google Groups "Akka User List" group. >>>>>>>>>>>> To unsubscribe from this group and stop receiving emails from >>>>>>>>>>>> it, send an email to [email protected]. >>>>>>>>>>>> To post to this group, send email to [email protected]. >>>>>>>>>>>> Visit this group at https://groups.google.com/group/akka-user. >>>>>>>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> -- >>>>>>>>>>> >>>>>>>>>>> Patrik Nordwall >>>>>>>>>>> Akka Tech Lead >>>>>>>>>>> Lightbend <http://www.lightbend.com/> - Reactive apps on the >>>>>>>>>>> JVM >>>>>>>>>>> Twitter: @patriknw >>>>>>>>>>> >>>>>>>>>>> [image: Lightbend] <http://www.lightbend.com/> >>>>>>>>>>> >>>>>>>>>>> -- >>>>>>>>>>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>>> >>>>>>>>>> Check the FAQ: >>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>>>> >>>>>>>>>> Search the archives: >>>>>>>>>>> https://groups.google.com/group/akka-user >>>>>>>>>>> --- >>>>>>>>>>> You received this message because you are subscribed to the >>>>>>>>>>> Google Groups "Akka User List" group. >>>>>>>>>>> To unsubscribe from this group and stop receiving emails from >>>>>>>>>>> it, send an email to [email protected]. >>>>>>>>>>> To post to this group, send email to [email protected]. >>>>>>>>>>> Visit this group at https://groups.google.com/group/akka-user. >>>>>>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> -- >>>>>>>>>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>> >>>>>>>>>> Check the FAQ: >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>>> >>>>>>>>>> Search the archives: >>>>>>>>>> https://groups.google.com/group/akka-user >>>>>>>>>> --- >>>>>>>>>> You received this message because you are subscribed to the >>>>>>>>>> Google Groups "Akka User List" group. >>>>>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>>>>> send an email to [email protected]. >>>>>>>>>> To post to this group, send email to [email protected]. >>>>>>>>>> Visit this group at https://groups.google.com/group/akka-user. >>>>>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> -- >>>>>>>>> >>>>>>>>> Patrik Nordwall >>>>>>>>> Akka Tech Lead >>>>>>>>> Lightbend <http://www.lightbend.com/> - Reactive apps on the JVM >>>>>>>>> Twitter: @patriknw >>>>>>>>> >>>>>>>>> [image: Lightbend] <http://www.lightbend.com/> >>>>>>>>> >>>>>>>>> -- >>>>>>>>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>> >>>>>>>>>> Check the FAQ: >>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>> >>>>>>>>>> Search the archives: >>>>>>>>> https://groups.google.com/group/akka-user >>>>>>>>> --- >>>>>>>>> You received this message because you are subscribed to the Google >>>>>>>>> Groups "Akka User List" group. >>>>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>>>> send an email to [email protected]. >>>>>>>>> To post to this group, send email to [email protected]. >>>>>>>>> Visit this group at https://groups.google.com/group/akka-user. >>>>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>>>> >>>>>>>> >>>>>>>> -- >>>>>>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>> >>>>>>>>>> Check the FAQ: >>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>> >>>>>>>>>> Search the archives: >>>>>>> https://groups.google.com/group/akka-user >>>>>>> --- >>>>>>> You received this message because you are subscribed to the Google >>>>>>> Groups "Akka User List" group. >>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>> send an email to [email protected]. >>>>>>> To post to this group, send email to [email protected]. >>>>>>> Visit this group at https://groups.google.com/group/akka-user. >>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>> >>>>>> >>>>>> -- >>>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>> >>>>>>>>>> Check the FAQ: >>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>> >>>>>>>>>> Search the archives: >>>> https://groups.google.com/group/akka-user >>>> --- >>>> You received this message because you are subscribed to the Google >>>> Groups "Akka User List" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected] <javascript:>. >>>> To post to this group, send email to [email protected] >>>> <javascript:>. >>>> Visit this group at https://groups.google.com/group/akka-user. >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>> >>> -- >>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>> >>>>>>>>>> Check the FAQ: >>> http://doc.akka.io/docs/akka/current/additional/faq.html >>> >>>>>>>>>> Search the archives: >>> https://groups.google.com/group/akka-user >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "Akka User List" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected] <javascript:>. >>> To post to this group, send email to [email protected] >>> <javascript:>. >>> Visit this group at https://groups.google.com/group/akka-user. >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- >> >>>>>>>>>> Read the docs: http://akka.io/docs/ >> >>>>>>>>>> Check the FAQ: >> http://doc.akka.io/docs/akka/current/additional/faq.html >> >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user >> --- >> You received this message because you are subscribed to the Google Groups >> "Akka User List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] <javascript:>. >> To post to this group, send email to [email protected] >> <javascript:>. >> Visit this group at https://groups.google.com/group/akka-user. >> For more options, visit https://groups.google.com/d/optout. >> > > -- >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>> Check the FAQ: >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user --- You received this message because you are subscribed to the Google Groups "Akka User List" group. 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