pppnnn pppnnn - 24 days ago 11
Scala Question

Akka actor pipeline and congested store actor

I am attempting to implement a message processing pipeline using actors. The steps of the pipeline include functions such as reading, filtering, augmentation and, finally, storage into a database.
Something similar to this: http://sujitpal.blogspot.nl/2013/12/akka-content-ingestion-pipeline-part-i.html

The issue is that the reading, filtering and augmentation steps are much faster than the storage step which results in having a congested store actor and an unreliable system.

I am considering the following option: have the store actor pull the processed and ready to store messages. Is this a good option? better suggestions?

Thank you

Answer

You may consider several options:

  • if order of messages doesn't matter - just execute every storage operation inside separate actor (or future). It will cause all data storage to be doing in parallel - i recommend to use separate thread pool for that. If some messages are amendments to others or participate in same transaction - you may create separate actors only for each messageId/transactionId to avoid pessimistic/optimistic lock problems (don't forget to kill such actors on transaction end or by timeout) .

  • use bounded mailboxes (back-pressure) - then you will block new messages from your input if older are still not processed (for example you may block the receiving thread til message will be acknowledged by last actor in the chain). It will move responsibility to source system. It's working pretty much good with JMS durables - messages are storing in reliable way on JMS-broker side til your system finally have them processed.

  • combine the previous two

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