For reference - and having conducted a lot of testing on various situations.
Both patterns would work - either delivering to a delegate actor that you have just created, or delivering to a fixed path - such as a cluster sharding location. There is a benefit to the latter - in that during recovery you may perform a 'create a delegate, deliver to delegate' and subsequently (still in recovery) 'confirm delivery' - leaving your delegate actor in essence orphaned/requiring cleanup. By sending the messages to yourself - should you deliver and confirm in recovery phase then you simply do not deliver the message to yourself and hence perform no action. I'm keen to point out that whatever message you deliver to yourself you should not persist if you follow this second pattern. Thanks kindly, Daniel Stoner On Wednesday, 22 June 2016 08:33:36 UTC+1, Daniel Stoner wrote: > > Hi all, > > The semantics of At-least once delivery still confuse me to some degree. I > understand that you utilise: > deliver(someActorPath, (Long id)-> someMessage.withId(id)) > > And then later > receive( > SomeMessageDone.class, > msg->confirmDelivery(msg.id) > ) > > My query relates to the ActorPath. It is my understanding that during a > restart of the server - at-least once delivery only attempts re-delivery > after recovery on the actor has finished. > EG A sharded persistent actor wakes up and goes through all of its > recovery messages. In these messages it would have chosen to deliver 5 > things - and confirm 3 of them. As such once RecoveryCompleted is received > - it then carries out the 2 deliveries of things which were not confirmed. > In this sense - the Long id for the deliveryId would always start at 0 > when an actor first wakes up (Which makes sense since it doesn't really > persist that id anywhere) > > Does this mean - that the following - creating a brand new actor to > delegate work to as part of delivery would make sense or not? > > ActorRef brandNewActorDedicatedJustToThisMessage = > system.actorOf(....props...) > delivery(brandNewActor.path(), someMessage) > > In this sense - the first call to deliver might be to path > /user/someRandomX - and after a restart the new attempt to delivery will be > to a completely different /user/someRandomY. The functionality would work > fine however. > > Or am I incorrect - and at-least once delivery will simply re-deliver to > the same path over and over again EG /user/someRandomX which no longer > exists after a restart? > In which case the only sensible path to send to would seem to be the > sharded actor itself - EG I should follow a pattern of: > deliver(self().path(), .....) > > Thanks kindly, > Daniel Stoner > -- > Daniel Stoner | Senior Software Engineer UtopiaIT | Ocado Technology > [email protected] | Ext 7969 | www.ocadotechnology.com > > > Notice: This email is confidential and may contain copyright material of > members of the Ocado Group. Opinions and views expressed in this message > may not necessarily reflect the opinions and views of the members of the > Ocado Group. > > > > If you are not the intended recipient, please notify us immediately and > delete all copies of this message. Please note that it is your > responsibility to scan this message for viruses. > > > > Fetch and Sizzle are trading names of Speciality Stores Limited, a member > of the Ocado Group. > > > > References to the “Ocado Group” are to Ocado Group plc (registered in > England and Wales with number 7098618) and its subsidiary undertakings (as > that expression is defined in the Companies Act 2006) from time to time. > The registered office of Ocado Group plc is Titan Court, 3 Bishops Square, > Hatfield Business Park, Hatfield, Herts. AL10 9NE. > -- Notice: This email is confidential and may contain copyright material of members of the Ocado Group. Opinions and views expressed in this message may not necessarily reflect the opinions and views of the members of the Ocado Group. If you are not the intended recipient, please notify us immediately and delete all copies of this message. Please note that it is your responsibility to scan this message for viruses. 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