[jira] [Created] (HELIX-409) Some messaging patterns are unreliable

["Kanak Biscuitwala (JIRA)" <ji...@apache.org>]

Kanak Biscuitwala created HELIX-409:
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             Summary: Some messaging patterns are unreliable
                 Key: HELIX-409
                 URL: https://issues.apache.org/jira/browse/HELIX-409
             Project: Apache Helix
          Issue Type: Bug
            Reporter: Kanak Biscuitwala


There is a usage pattern where a task is started, and Helix's messaging framework is used to post status updates. Specifically, the controller serves as the liason for status updates, as it checks completion status, and updates an overall status to indicate completion.

Having the controller in the middle of this workflow is the cause of several problems:
  - Polling of zookeeper
  - Writes to zookeeper for every status change
  - If the controller dies, the controller that comes up doesn't know that it has something to process, as much of this management work is done in memory

Generally speaking, this is probably not the right way at all to use Helix messaging, as "send and forget" point-to-point messaging works more naturally. However, if we actually want to support use cases like the one causing these problems, we need a fix.



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