Akka actors have 2 "mailboxes"/"queue" User messages System messages (signals)
System messages are always processed over user messages. System messages also have stronger delivery "guarantees". Cheers, √ On Tue, Jan 7, 2014 at 12:56 PM, Roger Alsing <[email protected]> wrote: > Oh, that explains it. > I thought that each message was delivered in sequence, which I'm pretty > sure I've seen described on a few places (?) > > Well, I'll try to explain what I mean more in detail > > pseudo code: > > class ActorA extends UntypedActor > { > ActorRef child = context.actorOf(... ActorB...); > public void onReceive(Object message) throws Exception { > ..stuff.. > child.tell(message,getSender()); > } > } > > class ActorB extends UntypedActor > { > public void onReceive(Object message) throws Exception { > //broken code (for whatever reason, some missing resource or something) > throw exception > } > } > > somewhere: > > for(int i=0;i<1000;i++) > actorA.Tell("hello",ActorRef.noSender); > > > If I get things right, what will happen here is that 1000 "hello" messages > will be passed to ActorA pretty quickly. > that is, the queue will fill up in very fast. > > once the first message arrives to onReceive, it will be forwarded to > ActorB, which throws because it is broken. > if B tries to notify A of this without priority, the message would be > placed at the end of the ActorA mailbox. > so there would be no way for ActorA to stop/restart ActorB before all of > the existing messages are handled.. > (That is ofcourse assuming that throwing exceptions is expensive and that > there is no priority to certain messages) > > But if it is like you say, a priority to supervision messages, then that > explains it. > But that makes me curious on how that is handled? > Is the mailbox a priority queue? > > Why I'm asking is that since I'm playing around with my .NET port of akka, > I got the described above behavior. and I wondered how it is solved in real > Akka and could not find any explanation in the code. > > > > > Den tisdagen den 7:e januari 2014 kl. 11:43:13 UTC+1 skrev drewhk: >> >> Hi Roger, >> >> I am also a bit unsure about the question, but system messages (the >> messages used by supervision for example) are handled with "priority" >> compared to user messages. I am not sure this answers your question though. >> >> -Endre >> >> >> On Tue, Jan 7, 2014 at 11:06 AM, √iktor Ҡlang <[email protected]>wrote: >> >>> Not sure I follow, can you create a code sample in Akka that shows the >>> perceived problem? >>> >>> >>> On Tue, Jan 7, 2014 at 8:45 AM, Roger Alsing <[email protected]> wrote: >>> >>>> How does the supervisor deal with congestion? >>>> >>>> Lets say that Actor A sends all it's incoming messages to child Actor B. >>>> And lets say we pass 1000 messages to actor A, then actor B will >>>> eventually also get 1000 messages. >>>> But if B for some reason throws, e.g. on each message, then actor B >>>> will throw a 1000 times unless stopped. >>>> >>>> This is where the supervisor should come in and save us, but if the >>>> overhead of throwing an exception takes longer than passing 1000 messages >>>> to actor A. >>>> Then actor B will not be able to notify it's parent that it has thrown >>>> before actor A has processed all of the initial 1000 messages. >>>> Thus, actor B will throw 1000 times because the parent is bussy >>>> processing those initial messages. >>>> >>>> Is this the expected behavior in Akka? >>>> Or is supervision done w/o passing messages back to the owner? >>>> >>>> I assume stopping/removing/restarting children needs to be done in the >>>> parent actors context and therefore use messaging to notify the parent? >>>> >>>> >>>> -- >>>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>> >>>>>>>>>> Check the FAQ: http://akka.io/faq/ >>>> >>>>>>>>>> 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 http://groups.google.com/group/akka-user. >>>> For more options, visit https://groups.google.com/groups/opt_out. >>>> >>> >>> >>> >>> -- >>> Cheers, >>> √ >>> >>> * Viktor Klang* >>> *Director of Engineering* >>> Typesafe <http://www.typesafe.com/> >>> >>> Twitter: @viktorklang >>> >>> -- >>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>> >>>>>>>>>> Check the FAQ: http://akka.io/faq/ >>> >>>>>>>>>> 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 http://groups.google.com/group/akka-user. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >> >> -- > >>>>>>>>>> Read the docs: http://akka.io/docs/ > >>>>>>>>>> Check the FAQ: http://akka.io/faq/ > >>>>>>>>>> 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 http://groups.google.com/group/akka-user. > For more options, visit https://groups.google.com/groups/opt_out. > -- Cheers, √ *Viktor Klang* *Director of Engineering* Typesafe <http://www.typesafe.com/> Twitter: @viktorklang -- >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>> Check the FAQ: http://akka.io/faq/ >>>>>>>>>> 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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