[jira] [Commented] (EDGENT-382) A RuntimeException thrown while processing a tuple brings down the whole topology

["Victor Dogaru (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/EDGENT-382?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15892852#comment-15892852 ] 

Victor Dogaru commented on EDGENT-382:
--------------------------------------

[EDGENT-8|https://issues.apache.org/jira/browse/EDGENT-8] provides a mechanism to prevent a Quarks application from becoming unavailable.  Do we need finer granularity resilience?

> A RuntimeException thrown while processing a tuple brings down the whole topology
> ---------------------------------------------------------------------------------
>
>                 Key: EDGENT-382
>                 URL: https://issues.apache.org/jira/browse/EDGENT-382
>             Project: Edgent
>          Issue Type: Bug
>          Components: Runtime
>            Reporter: Dale LaBossiere
>         Attachments: DlabossExceptionTest.java
>
>
> I encountered the above in the context of the WIoTP connector, and
> there may be a problem there as well, but it’s trivial to demonstrate the
> problem in a more general context.
> i.e., a RuntimeException thrown from a Topology.poll(), generate(), source() or from an unisolated user function implementation downstream of the source, like a map() or sink()'s function, causes the topology to immediately terminate.  That typically causes the process to terminate.
> It's unclear to me which parts of the runtime should be doing what with respect to this.
> Things need to be more resilient in the face of transient errors, particularly wrt transient connector problems.  As an example MqttPublisher.accept() achieved resiliency in the face of transient connection problems by logging instead of throwing.  IotpDevice connector just throws... which at a certain level is OK/desirable... if the runtime were to handle resiliency issues.
> Note, a RuntimeException from a Topology.events() supplier or even a downstream function doesn't result in topology termination.  That's because the runtime thread blocking awaiting the next supplied tuple doesn't see the RuntimeException.  And for the downstream case, the stream is Isolated so again the runtime thread doesn't see the exception.  That said, the thread internal to Isolate silently terminates in the face of a downstream exception.  ugh.  (Barrier looks to have a similar problem).
> There needs to be some clear / prominent doc on all of this, what the design / behavior is supposed to be, and then we can address any issues in the light of that understanding.



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