+1 for PersistentActor Heiko
On Tue, May 20, 2014 at 10:50 PM, Roland Kuhn <goo...@rkuhn.info> wrote: > Hi Odd, > > that is a very good question: I was operating under the premise that > EventsourcedProcessor is used quite a bit by now and renaming it might not > be met with unlimited enthusiasm. The replacement for PersistentChannel > will need to be named differently since the “persistent” in the name is > confusing, but the details will have to wait until we have settled on its > precise nature. > > Perhaps we can do a “quick deprecation” for EventsourcedProcessor in > 2.4-M1 (since it is marked “experimental” for this very reason), aliasing > it until removal. I quite like PersistentActor, Processor is too generic. > > Opinions? > > Regards, > > Roland > > 20 maj 2014 kl. 22:39 skrev Odd Möller <odd.mol...@gmail.com>: > > Hi! > > Just wanted to say that I love the idea of simplifying the abstractions as > suggested in this thread (all our processors are already of the event > sourced kind). One thing that occurred to me is if a similar simplification > can be done on the naming of the concepts: now that the names "Processor" > and "Channel" are unused, should the remaining concept still be called > "EventsourcedProcessor"? What about calling it "Processor", > "PersistentActor" or "EventsourcedActor" instead? Ditto regarding the > reborn "PersistentChannel". > > Greetings > Odd > > > On Tue, May 20, 2014 at 8:47 PM, 何品 <hepin1...@gmail.com> wrote: > >> I am using the persistent channel as a durable queue,and for it was not >> recommend ,I switch to redis . >> >> 在 2014年5月21日星期三UTC+8上午2时32分38秒，rkuhn写道： >>> >>> Hi Alex, >>> >>> I have filed the ticket for Processor’s removal ( >>> https://github.com/akka/akka/issues/15230), which also talks about >>> Channel since that was only needed to contain the side-effecting replay >>> nature of command sourced processors. Your description below is rather >>> terse, so it is not fully clear to me how you are using Channel in this >>> case and what a replacement should be, can you elaborate? >>> >>> There is also the discussion ticket for reinventing PersistentChannel ( >>> https://github.com/akka/akka/issues/15231) which might be of interest >>> in this context. My motivation here is to not remove needed functionality >>> without improved replacement. >>> >>> Regards, >>> >>> Roland >>> >>> 9 maj 2014 kl. 12:15 skrev ahjohannessen <ahjoha...@gmail.com>: >>> >>> Hi Roland, >>> >>> We use Channel in conjunction with Eventsourced Processor (EP) in our >>> applications in receiveRecover. >>> It would be sad to see it go away without a reasonable alternative. >>> >>> One scenario in our apps is that we use DDD/ES and have a lot of EPs of >>> same type, e.g. 10000 instances, >>> that are loaded on demand by a supervisor. >>> >>> In order to have a single view on all of these, we inject an actor that >>> wraps a single channel / aggregator EP combo >>> into these instances on creation. This makes it possible to react to >>> changes, even in case of JVM crashes, >>> in that family of EPs as well as having a global view of that family. >>> >>> >>> On Friday, May 9, 2014 9:13:17 AM UTC+1, rkuhn wrote: >>>> >>>> >>>> 9 maj 2014 kl. 09:58 skrev Martin Krasser <kras...@googlemail.com>: >>>> >>>> >>>> On 09.05.14 09:25, Roland Kuhn wrote: >>>> >>>> >>>> 9 maj 2014 kl. 09:08 skrev Martin Krasser <kras...@googlemail.com>: >>>> >>>> >>>> On 09.05.14 08:41, Roland Kuhn wrote: >>>> >>>> Hi Martin, >>>> >>>> 9 maj 2014 kl. 08:05 skrev Martin Krasser <kras...@googlemail.com>: >>>> >>>> Hi Roland, >>>> >>>> thanks for starting a discussion on this. Here are some initial >>>> thoughts on your proposal: >>>> >>>> "... very same throughput optimization by applying the state changes >>>> before persisting them ..." >>>> >>>> I think we agree that whatever changes are going to be made in the >>>> future, we must keep the throughput optimizations (by batching >>>> writes/updates). As you said, with an EP, this can only be achieved by >>>> applying events to current state *before* persisting them. Furthermore, to >>>> enable batching, an EP must therefore be able to process new commands while >>>> (previous) events are about to be persisted. This however has a very >>>> important consequence for commands that read current state. If we allow >>>> events to be applied to current state *before* persisting them, we allow >>>> clients to read state from that EP that may not be re-readable after a >>>> crash. For example: >>>> >>>> - EP receives update command, derives event and applies it immediately >>>> to current state >>>> - EP (asynchronously) persists event >>>> - EP receives a read command (while event persistence is in progress) >>>> - EP (successfully) returns read response to requestor >>>> - EP JVM crashes before event was successfully persisted >>>> - EP state cannot be reconstructed i.e. previous read cannot be >>>> repeated. >>>> >>>> >>>> This is only true if the recovery is incomplete: the update command >>>> will not have been acknowledged at this point, so if someone cared about it >>>> they will send it again during recovery and the EP will eventually end up >>>> in a state where the read will return the same value again. If this type of >>>> consistency is not good enough, then you can always defer reads within the >>>> write model until after persistence is completed, meaning that the read is >>>> only performed once a corresponding read “event” has gone through the >>>> journal. We could allow events that are only looped through to make this >>>> work, just like non-Persistent commands are looped today (and for the same >>>> reason). >>>> >>>> >>>> Delaying reads is only an option when reads are made via messages to a >>>> (E)P. If my processor manages state via an STM ref where only the processor >>>> updates the STM ref but reads go directly to the STM ref, then you cannot >>>> delay reads. >>>> >>>> >>>> In this scenario you would delay updating the STM ref until after the >>>> persistence loop, which is exactly the same as for a current >>>> command-sourced Processor: the read gets delayed until after the writes are >>>> processed, in the same way the STM ref update gets delayed by the write >>>> having to go through the journal. Effects, consistency and latency are the >>>> same in both implementations. >>>> >>>> >>>> That's true. So, to achieve >>>> >>>> - repeatable reads >>>> - low read latency and >>>> - high write throughput >>>> >>>> reads can go to the STM refs directly and EP must update the STM ref >>>> only after having persisted the events. If one *additionally* wants to >>>> achieve >>>> >>>> - read-your-own-write consistency (assuming a client issues an update >>>> command, immediately followed by a read command) >>>> >>>> one would need a way to loop read commands through the journal as well >>>> before serving them (which probably requires an addition to the API then). >>>> Alternatively, a client only issues a read after having received a >>>> write-ack (at the cost of an additional roundtrip). >>>> >>>> >>>> This is an interesting remark: normally read-your-writes is only >>>> guaranteed for reads submitted after having received the ACK for the write, >>>> so what we are providing here is actually a qualitative improvement on that >>>> status quo that is only possible in Reactive systems (normally the ACK is >>>> signaled by a synchronous non-exceptional method return). >>>> >>>> Anyway, I think you convinced me, as usual :) Great proposal, Dr Kuhn! >>>> >>>> >>>> And as usual you helped in refining the proposal: the addition of >>>> looping non-persistent events through the journal is an important one, >>>> thanks for providing the use-case! >>>> >>>> So, to summarize, we can incorporate all current functionality provided >>>> by Processor and Channel into EventsourcedProcessor by adding the following >>>> two features: >>>> >>>> >>>> - the ability to opt out of stashing everything while waiting for >>>> persist()ing >>>> - the ability to loop non-persistent events through the journal >>>> >>>> >>>> Everyone, please consider what this would mean for your code base and >>>> comment, now is the right time to speak up! The same goes for opinions on >>>> whether PersistentChannel pulls its weight or not (as argued earlier in >>>> this thread). >>>> >>>> Regards, >>>> >>>> Roland >>>> >>>> >>>> Cheers, >>>> Martin >>>> >>>> -- >>>> >>>>>>>>>> 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 akka-user+...@googlegroups.com. >>>> To post to this group, send email to akka...@googlegroups.com. >>>> Visit this group at http://groups.google.com/group/akka-user. >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>>> >>>> >>>> >>>> *Dr. Roland Kuhn* >>>> *Akka Tech Lead* >>>> Typesafe <http://typesafe.com/> – Reactive apps on the JVM. >>>> twitter: @rolandkuhn >>>> <http://twitter.com/#!/rolandkuhn> >>>> >>>> >>> -- >>> >>>>>>>>>> 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 akka-user+...@googlegroups.com. >>> To post to this group, send email to akka...@googlegroups.com. >>> Visit this group at http://groups.google.com/group/akka-user. >>> For more options, visit https://groups.google.com/d/optout. >>> >>> >>> >>> >>> *Dr. Roland Kuhn* >>> *Akka Tech Lead* >>> Typesafe <http://typesafe.com/> – Reactive apps on the JVM. >>> twitter: @rolandkuhn >>> <http://twitter.com/#!/rolandkuhn> >>> >>> >> -- >> >>>>>>>>>> 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 akka-user+unsubscr...@googlegroups.com. >> To post to this group, send email to akka-user@googlegroups.com. >> Visit this group at http://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 akka-user+unsubscr...@googlegroups.com. > To post to this group, send email to akka-user@googlegroups.com. > Visit this group at http://groups.google.com/group/akka-user. > For more options, visit https://groups.google.com/d/optout. > > > > > *Dr. Roland Kuhn* > *Akka Tech Lead* > Typesafe <http://typesafe.com/> – Reactive apps on the JVM. > twitter: @rolandkuhn > <http://twitter.com/#!/rolandkuhn> > > -- > >>>>>>>>>> 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 akka-user+unsubscr...@googlegroups.com. > To post to this group, send email to akka-user@googlegroups.com. > Visit this group at http://groups.google.com/group/akka-user. > For more options, visit https://groups.google.com/d/optout. > -- Heiko Seeberger Twitter: @hseeberger Blog: blog.heikoseeberger.name -- >>>>>>>>>> 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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