Thank you. On Thursday, March 13, 2014 12:42:23 AM UTC+8, Martin Krasser wrote: > > Hi Daniel, > > On 12.03.14 15:41, Daniel Wang wrote: > > Akka persistence module provides at-lease-once message delivery, which > means a message may be delivered multiple times. Care must be taken in the > application logic to avoid processing the same message more than once. One > obvious (to me) way to deal with this is to keep a last-processed-seq-nr in > a processor (say A) or view. > > > tracking the last processed sequence number only works with a View. > Channel destinations cannot make any ordering assumtpions, hence, tracking > the last processed sequence number doesn't work. For example, a message > delivered to a remote destination can be lost and is redelivered later i.e. > the destination will see that redelivered message out of order. > > But a processor may receive ConfirmablePersistent messages from more > than one Channel (say X, Y, Z), so A will have to keep 3 > 'last-processed-seq-nr' variable to keep track events from X, Y, Z > respectively. However, I found ConfirmablePersistent interface doesn't > expose it channel id, so I don't know how to update these 3 vars? > > > At the moment, a sender needs to include an application-specific source id > in the message so that a destination can distinguish different senders. > Since ConfirmablePersistent messages can only be received via channels, it > makes sense to add public channelId field in the future. > > > Did I miss something? > > If the above logic is correct, will Akka Persistence module do the > last-processed-id tracking automatically in the future so we have > exactly-once message delivery? > > > Exactly-once delivery is very expensive and limits scalability. If you > haven't already done, you may want to read Pet Helland's paper Life > beyond Distributed > Transactions<http://www-db.cs.wisc.edu/cidr/cidr2007/papers/cidr07p15.pdf>for > some motivations behind supporting at-least-once delivery semantics > only. > > -- > >>>>>>>>>> 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 <javascript:>. > To post to this group, send email to akka...@googlegroups.com<javascript:> > . > Visit this group at http://groups.google.com/group/akka-user. > For more options, visit https://groups.google.com/d/optout. > > > -- > 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://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.
