Thanks for pointing out that feature, I totally missed it.

That's awesome.

On Monday, April 24, 2017 at 8:17:37 PM UTC+10, Arnout Engelen wrote:
>
> Might 
> http://doc.akka.io/docs/akka/current/scala/cluster-sharding.html#Remembering_Entities
>  
> help?
>
>
> Arnout
>
> On Mon, Apr 24, 2017 at 2:32 AM, Edouard Kaiser <edouard...@skiddoo.com.au 
> <javascript:>> wrote:
>
>> Hi everyone,
>>
>> We are trying to achieve "at-least-once" delivery with cluster sharding 
>> and persistent actor.
>>
>> Context: 
>>
>> *ActorSystemA*:
>> - PersistentActorA
>>
>> *ActorSystemB*:
>> - ActorB
>>
>> PersistentActorA receives a message, persist it, then send it to ActorB. 
>> Once ActorB processed it, it sends back an ACK to PersistentActorA which 
>> then uses *confirmDelivery*. 
>>
>> Works like a charm in a non-cluster situation. Just one JVM to another 
>> with akka-remote, PersistentActorA has a fixed persistenceId.
>>
>> Now we want to scale this situation. Multiple *ActorSystemA* are running 
>> at the same time, part of the same cluster. Now we have to use sharding to 
>> make sure there is only one *PersistentActorA *instance in the cluster 
>> for the same entity id.
>>
>> Problem appears when we start scaling because of the characteristic of 
>> our payload. It's a one-off payload. The ID inside, used to compute the 
>> entity ID for sharding, it's not an ID which will appear again in another 
>> message. 
>>
>> That means, if for whatever reason this scenario happens:
>> 1. message is persisted by the *PersistentActorA *for a particular 
>> entity ID (let's say the ID is 1)
>> 2. message can't be sent (ActorSystemB is down)
>> 3. The *PersistentActorA *for the entity ID 1 is going down (crashed 
>> application...)
>>
>> Because there won't be any other payload with entity ID == 1, this 
>> *PersistentActorA* will never be created again. So, the messages won't 
>> be replayed form the journal, and the message will never get delivered.
>>
>> Am I right? Or we are missing something?
>>
>> Thanks for your help,
>>
>> -- 
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>
>
>
>

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>>>>>>>>>>      Check the FAQ: 
>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
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