Hi Konrad,
So I want to create a distributed state machine based on RAFT which I know
you're pretty familiar with. I want to use this facility when reconciling
logs. My understanding is that when an AppendEntries fails the Leader tries
to send the Follower a previous entry from the log till we reach the point
where the previous term and sequence match in the two logs. I want to use
the read facility in that scenario.
I'm not sure reading until a certain sequence number will be performant.
I know you must have done more thinking on this since you have worked both
on akka-persistence and akka-raft :) so I would appreciate your input.
Thanks,
-Moiz
On Monday, 7 July 2014 10:18:31 UTC-7, Konrad Malawski wrote:
>
> Hello Moiz,
> an event detached from it’s lineage does not make much sense for building
> up state - which is how persistent actors are designed to be used.
> An persistent actor’s state, and your “domain state”, should be built up
> from such series of events (and snapshots).
>
> We do support playback “until” a given sequence number, you can achieve
> this via:
>
> class Peter extends PersistentActor {
> override def preStart() {
> self ! Recover(toSequenceNr = 20)
> }
>
> def receiveCommand = { }
> def receiveRecover = {
> case m if lastSequenceNr == 15 => // ...
>
> case _ => // ...
> }
>
> If you only want one of these items, you can just ignore the others like
> shown in the example above.
> But reading out one specific event is not something we will want to
> support (we are actively removing methods that target “one message” in
> favour of ranged operations (see deprecated deleteMessage vs.
> deleteMessages(toSequenceNr)).
>
>
> May I ask why you need to read exactly one event?
> It would help to understand your use case, and then advice. :-)
>
>
>
> On Mon, Jul 7, 2014 at 7:00 PM, Moiz Raja <[email protected] <javascript:>
> > wrote:
>
>> I am using akka-persistence and I have a need to read a specific journal
>> entry but I do not see a way in akka-persistence to do that.
>>
>> Is there any reason why an API has not been provided for this? Are there
>> any plans to provide this in an upcoming release?
>>
>> Thanks,
>> -Moiz
>>
>> --
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>
>
>
> --
> Cheers,
> Konrad 'ktoso' Malawski
> hAkker @ Typesafe
>
> <http://typesafe.com>
>
--
>>>>>>>>>> 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
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