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https://issues.apache.org/jira/browse/SAMZA-2092?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Bharath Kumarasubramanian resolved SAMZA-2092.
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Resolution: Fixed
Fixed in SAMZA-2055
> Make window operator thread safe
> --------------------------------
>
> Key: SAMZA-2092
> URL: https://issues.apache.org/jira/browse/SAMZA-2092
> Project: Samza
> Issue Type: Bug
> Reporter: Bharath Kumarasubramanian
> Assignee: Bharath Kumarasubramanian
> Priority: Major
>
> Currently, window operator maintains some state which when modified
> concurrently could result in undesired behavior. This is a problem for high
> level stream applications with task.max.concurrency > 1.
> Here is a sample stacktrace that illustrates NPE caused due to concurrent
> modification on callback state queue maintained by trigger handler.
> {code:java}
> Caused by: java.lang.NullPointerException at
> org.apache.samza.operators.impl.TriggerScheduler$TriggerCallbackState.compareTo(TriggerScheduler.java:111)
> at
> org.apache.samza.operators.impl.TriggerScheduler$TriggerCallbackState.compareTo(TriggerScheduler.java:83)
> at java.util.PriorityQueue.siftUpComparable(PriorityQueue.java:656)
> at java.util.PriorityQueue.siftUp(PriorityQueue.java:647) at
> java.util.PriorityQueue.offer(PriorityQueue.java:344) at
> java.util.PriorityQueue.add(PriorityQueue.java:321) at
> org.apache.samza.operators.impl.TriggerScheduler.scheduleCallback(TriggerScheduler.java:55)
> at
> org.apache.samza.operators.triggers.TimeTriggerImpl.onMessage(TimeTriggerImpl.java:53)
> at
> org.apache.samza.operators.impl.WindowOperatorImpl$TriggerImplHandler.onMessage(WindowOperatorImpl.java:400)
> at
> org.apache.samza.operators.impl.WindowOperatorImpl.handleMessage(WindowOperatorImpl.java:170)
> at
> org.apache.samza.operators.impl.OperatorImpl.onMessage(OperatorImpl.java:184){code}
> In the above scenario, one thread is adding a callback state to the priority
> queue, while another thread is canceling one of the existing callback state.
> Due to concurrent modification, add operation fails with NPE since the
> reference used for comparison is null.
> As part of this ticket, we also want to make sure all high level operators
> wherever applicable is thread safe. It is a pre-requisite for async API
> support in high level applications.
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