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https://issues.apache.org/jira/browse/LENS-1169?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15318248#comment-15318248
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Hadoop QA commented on LENS-1169:
---------------------------------

Applied patch: 
[LENS-1169.01.patch|https://issues.apache.org/jira/secure/attachment/12808630/LENS-1169.01.patch]
 and ran command: mvn clean install -fae. Result: Failure. Build Job: 
https://builds.apache.org/job/PreCommit-Lens-Build/496/

> Stopping Query Service is incorrect
> -----------------------------------
>
>                 Key: LENS-1169
>                 URL: https://issues.apache.org/jira/browse/LENS-1169
>             Project: Apache Lens
>          Issue Type: Bug
>            Reporter: Rajat Khandelwal
>            Assignee: Rajat Khandelwal
>         Attachments: LENS-1169.01.patch
>
>
> Stopping lens server basically stops all services. For query service, the 
> current flow is this:
> * Preapre stopping: 
>   ** Interrupt All threads (query submitter, purger, status poller etc)
> * Persist state
> * Stop
>   ** join all threads ( as mentioned above)
> Each of the threads is basically running in a large loop like the following:
> {noformat}
> while (!stopped && !this.isInterrupted()) {
>   try {
>   } catch(InterruptedException) {
>     return
>   }
> }
> {noformat}
> Now, interrupting a thread will cause InterruptException in the thread only 
> when the thread is waiting/sleeping.
> So, the thread can exit in two ways: 
> * By receiving interrupt
> * If an interrupt isn't received, it'll complete the current iteration loop 
> and then exit. 
> So there can be a scenario like the following (I faced such a scenario while 
> working on LENS-904): 
> * Stop is called from outside
> * Prepare stopping. Let's say QuerySubmitter didn't receive the interrupt and 
> will exit after completing its current iteration.
> * Persist:
>   ** Persist part1: Persisting driver states. e.g. HiveDriver keeps a map of 
> query handle to hive operation handle. 
> * QuerySubmitter submits the query to hive, changes the state of query to 
> LAUNCHED and exits. 
> * Persist: 
>   ** Persist part 2: Persisting queries. This persists the query mentioned in 
> the above point as LAUNCHED.
> Now, on start, the states will be read back, query's state will be LAUNCHED, 
> and HiveDriver won't have the operation handle corresponding to this query. 
> This will cause the query to fail in next status update. 
> Proposed Solution:
> Interrupt and join the threads before persisting in the prepareStopping 
> phase. 



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