Just to add to Martin's CouchDB comment, another technology you may want to look at is ZeroMq which provides a socket abstraction allowing messages sent to a socket to be queued in case remote peer is not available - http://api.zeromq.org/3-2:zmq-socket. And it is nicely integrated with Akka - http://doc.akka.io/docs/akka/snapshot/scala/zeromq.html
Cheers Oleg On Wed, Feb 12, 2014 at 1:51 AM, Martin Krasser <[email protected]>wrote: > Hi Jospeh, > > > On 11.02.14 23:48, Joseph Pachod wrote: > > Hi Oleg > > Thanks for your answer :) > > Well, I worked on some homegrown EDA framework which had support for > master/master and events replaying, so I guess I was starting with too much > expectation. > > Anyway, regarding akka-persistence, there's no support out of the box for > master/master. > > > I'm still missing an answer to Rolands question: what *exactly* do you > want to achieve?. Anyway, here are a few thoughts. > > 1.) master/master > > Using a replicated > journal<https://gist.github.com/krasserm/8612920#file-akka-persistence-plugins-md>, > processors with different processor ids can of course write to different > nodes. Not all writes have to go through the same node, this restriction > only applies to processors with the same processor id. So it really depends > on what you mean by master/master support. > > When updating processors with the same processor id on different nodes, > you have to answer at least these questions: > > - does it matter if processors with the same processor id on different > nodes see updates in different order. If yes, you'll need coordination > among these processors (= expensive) > - what data structures for processor state shall I use if my processors > may receive updates in any order? You may want to look at CRDTs and related > work <https://github.com/jboner/akka-crdt> done by Jonas. > > Addressing these questions goes beyond the intended scope of > akka-persistence. It was intended for fast and scalable single actor state > persistence (of course, with migration/fail-over support in a cluster). If > you want to maintain read-only replicas of a processor you should use > views <http://doc.akka.io/docs/akka/snapshot/scala/persistence.html#views> > . > > Keeping state consistent across (writable) processors is an > application-level concern. You can implement that yourself but I recommend > that you take a look at the numerous replicated NoSQL and SQL databases out > there as an alternative. > > 2.) Offline features > > You probably want to use a replicated journal that is able to have some of > its nodes temporarily separated from others and still support writes (e.g. > look at CouchDB's offline features, to mention only one example). If those > journal nodes are re-connected they would synchronize logged messages > (captured offline) with the other journal nodes. After re-connecting, > remote views would be automatically updated then. > > Hope that helps, > > Cheers, > Martin > > > If a local instance was to create new events and then, way later, pushed > them to some other instance, I would have to handle all the persistence of > this already existing event myself, and it's a hard topic I feel. Shall I > keep track of the original instance in the event stored ? Is it actually > the same event or something else... ? Plenty of questions : to have them > already tackled, if only partly, would be of a great help :$ It's almost to > the point where having to do it all from scratch make me wonder whether > akka would be right the right tool for the job. There may be easier ways... > > Thanks again ! > joseph > > > > On Tue, Feb 11, 2014 at 12:27 AM, Oleg Zhurakousky < > [email protected]> wrote: > >> I don't think there is anything to support. May be Akka-eng will chime >> in, but IMHO Akka is not a product but a library and a framework which >> allows you to build products. Git is a product and in theory you can easily >> emulate its architecture using Akka. >> Also, what Akka does provide is akka-persistence module which essentially >> allows you to preserve/persist the state of the mailbox, so it could be >> replayed (restored) for messages that didn't get a chance to process before >> system went down. So you may want to look at it and see if this is >> something that fits your use case. >> >> Cheers >> Oleg >> >> >> On Mon, Feb 10, 2014 at 6:00 PM, Joseph Pachod >> <[email protected]>wrote: >> >>> Hi Oleg >>> >>> That's part of it indeed. However, I haven't seen anything related to >>> replaying history with the new events in akka so far, so I was planning to >>> only push events which don't need replaying. Actually I haven't seen >>> something similar in Akka at all to be honest. This kind of >>> "disconnected/extra master" doesn't seem to be supported by akka AFAIK. Am >>> I right ? >>> >>> Best, >>> >>> >>> On Mon, Feb 10, 2014 at 2:11 PM, Oleg Zhurakousky < >>> [email protected]> wrote: >>> >>>> I think what you are talking about is classical event sourcing or a >>>> variation of it. Each new piece of data is a new event persisted somewhere >>>> (e.g., file) on the local system. Then when remote system comes online the >>>> event source stored up until this point would have to be replayed for the >>>> remote system, thus preserving the over-time state of the event stream >>>> allowing access to both current state as well as point-in-time. >>>> Is that what you trying to accomplish or your pieces of data are >>>> completely independent from one another (no historically significant >>>> timeline)? >>>> >>>> Cheers >>>> Oleg >>>> >>>> >>>> On Mon, Feb 10, 2014 at 4:54 AM, joseph <[email protected]>wrote: >>>> >>>>> Hi Roland >>>>> >>>>> Thanks a lot for your answer. >>>>> >>>>> The end target would be to have the data on the local system and >>>>> allowing creation of new data while offline. Then, on being online again, >>>>> the diff would be pushed and resolved. I had played with akka-persistence >>>>> regarding this application and I was wondering how I would implement such >>>>> an use case with it. >>>>> >>>>> Thanks again >>>>> >>>>> best >>>>> >>>>> >>>>> >>>>> >>>>> On Monday, February 10, 2014 8:03:32 AM UTC+1, rkuhn wrote: >>>>> >>>>>> Hi Joseph, >>>>>> >>>>>> what exactly do you want to achieve? I'm asking because Akka itself >>>>>> does not really have any end-user features, it is only a library for >>>>>> building your own functionality. The precise meaning of master/master or >>>>>> "disconnected mode" depends very much on what you are building with Akka, >>>>>> not on Akka itself. >>>>>> >>>>>> Regards, >>>>>> >>>>>> Roland >>>>>> >>>>>> 9 feb 2014 kl. 21:57 skrev joseph <[email protected]>: >>>>>> >>>>>> Hi >>>>>> >>>>>> While working on the train the other day I realized how much I missed >>>>>> git disconnected capacities. >>>>>> >>>>>> Ever since, this has stuck into my mind and I'm thinking about how to >>>>>> implement such mechanism. >>>>>> >>>>>> I looked around regarding akka but apparently master/master and >>>>>> disconnected stuff aren't too much spoken of. Did I miss something >>>>>> obvious >>>>>> ? Are they some best practices around or, even better, examples ? >>>>>> >>>>>> Thanks in advance >>>>>> joseph >>>>>> >>>>>> -- >>>>>> >>>>>>>>>> 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. >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> *Dr. Roland Kuhn* >>>>>> *Akka Tech Lead* >>>>>> Typesafe <http://typesafe.com/> - Reactive apps on the JVM. >>>>>> twitter: @rolandkuhn >>>>>> <http://twitter.com/#%21/rolandkuhn> >>>>>> >>>>>> -- >>>>> >>>>>>>>>> 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 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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. > > > -- > Martin Krasser > > blog: http://krasserm.blogspot.com > code: http://github.com/krasserm > twitter: http://twitter.com/mrt1nz > > -- > >>>>>>>>>> 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: 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