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https://issues.apache.org/jira/browse/ACCUMULO-2876?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14025629#comment-14025629
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Eric Newton commented on ACCUMULO-2876:
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I like the 2nd option (always use the site configuration).
> Unexpected looping from HdfsZooInstance.getInstanceID()
> -------------------------------------------------------
>
> Key: ACCUMULO-2876
> URL: https://issues.apache.org/jira/browse/ACCUMULO-2876
> Project: Accumulo
> Issue Type: Improvement
> Components: client
> Affects Versions: 1.6.0
> Reporter: Bill Havanki
> Assignee: Bill Havanki
> Priority: Minor
>
> While working ACCUMULO-2615, I encountered a weird looping behavior rooted at
> {{HdfsZooInstance.getInstanceID()}} that seems to accidentally avoid a stack
> overflow. I'm a bit blocked at the moment on -2615 since my work exposed the
> loop.
> Here's a summary of the loop. The unit test {{SystemCredentialsTest}} in the
> tserver module exercises it.
> * Start at {{HdfsZooInstance.getInstanceID()}}, which calls to an internal
> {{_getInstanceID()}} the first time.
> * A volume manager is needed to find the instance ID in HDFS, so
> {{VolumeManagerImpl.get()}} is called.
> * That call needs the "system" configuration, so a call to
> {{ServerConfiguration.getSystemConfiguration()}} is made, passing the
> {{HdfsZooInstance}} object.
> * The system configuration is a {{ZooConfiguration}} object, and that is
> created from {{ZooConfiguration.getInstance()}}.
> * That factory method creates a {{ZooConfiguration}} object, saved as a
> static field. The code then tries to get the instance ID for the passed-in
> instance, which is the {{HdfsZooInstance}} object. So we're back at the top
> of the loop.
> In the last step of the second iteration of the loop, the factory method sees
> that the static field for the singleton instance of {{ZooConfiguration}} was
> set in the first iteration, so it returns it and doesn't look for the
> instance ID. That stops the looping and the call stack unwinds.
> (My refactoring work has trouble with this because it gets rid of the single
> static field in favor of a map of objects keyed by instance ID.)
> This loop indicates a mutual dependency between configurations, the volume
> manager, and {{HdfsZooInstance}} that should be resolved.
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