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https://issues.apache.org/jira/browse/NIFI-16294?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Handermann resolved NIFI-16294.
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Fix Version/s: 2.12.0
Resolution: Fixed
> NPE in SiteToSiteStatusReportingTask when root flow is unavailable
> ------------------------------------------------------------------
>
> Key: NIFI-16294
> URL: https://issues.apache.org/jira/browse/NIFI-16294
> Project: Apache NiFi
> Issue Type: Bug
> Affects Versions: 2.11.0
> Environment: Observed when running 2.9.0 on Kubernetes, but
> objectively unrelated to the environment.
> Reporter: Sönke Liebau
> Assignee: Sönke Liebau
> Priority: Minor
> Fix For: 2.12.0
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> We recently encountered infrequent NullPointerExceptions when using the
> SiteToSiteStatusReportingTask in NiFi. We looked at the code and investigated
> in the cluster and usually those Exceptions correlated to cluster nodes
> restarting and rejoining the cluster.
> {code:java}
> SiteToSiteStatusReportingTask[id=xxx] Error running task
> SiteToSiteStatusReportingTask[id=xxx]: java.lang.NullPointerException
> {code}
> *Other issues*
> NIFI-7105 sounds very similar to this, but is not in fact related.
> *Root cause*
> We think we found the root cause and a possible fix, I'll open a PR to
> facilitate discussion on the code as well soon.
> The SiteToSiteStatusReportingTask calls
> context.getEventAccess().getControllerStatus() in
> [onTrigger|https://github.com/apache/nifi/blob/f5e20e3687f3eee9fecb3a6b59a5b542390616ef/nifi-extension-bundles/nifi-site-to-site-reporting-bundle/nifi-site-to-site-reporting-task/src/main/java/org/apache/nifi/reporting/SiteToSiteStatusReportingTask.java#L126],
> which returns
> null when the root process group isn't available (e.g. during startup before
> the flow is fully initialized, or when nodes join).
> The line immediately following that line guards against `null` when
> retrieving the name, but [further
> down|https://github.com/apache/nifi/blob/f5e20e3687f3eee9fecb3a6b59a5b542390616ef/nifi-extension-bundles/nifi-site-to-site-reporting-bundle/nifi-site-to-site-reporting-task/src/main/java/org/apache/nifi/reporting/SiteToSiteStatusReportingTask.java#L146]
> the result of getControllerStatus is passed on directly to deserialization,
> which throws an Exception in the case of `null`.
> *Fix*
> For a potential fix I looked at the
> [SiteToSiteMetricsReportingTask|https://github.com/apache/nifi/blob/f5e20e3687f3eee9fecb3a6b59a5b542390616ef/nifi-extension-bundles/nifi-site-to-site-reporting-bundle/nifi-site-to-site-reporting-task/src/main/java/org/apache/nifi/reporting/SiteToSiteMetricsReportingTask.java#L160]
> , which already guards against `null` and skips execution in that case
> Something similar should be done in the StatusReporting task to skip the
> trigger, when the status cannot be retrieved.
> I'm happy to open a PR to discuss directly on the code.
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