[jira] [Commented] (LUCENE-3373) waitForMerges deadlocks if background merge fails

["Michael McCandless (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-3373?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13089662#comment-13089662 ] 

Michael McCandless commented on LUCENE-3373:
--------------------------------------------

Hmm nice catch!

Any ides on how should we fix this...?  What do we want to happen?  Should waitForMerges() return if any merge hits an exc?  It could return a boolean indicating an error occurred?

> waitForMerges deadlocks if background merge fails
> -------------------------------------------------
>
>                 Key: LUCENE-3373
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3373
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: core/index
>    Affects Versions: 3.0.3
>            Reporter: Tim Smith
>
> waitForMerges can deadlock if a merge fails for ConcurrentMergeScheduler
> this is because the merge thread will die, but pending merges are still available
> normally, the merge thread will pick up the next merge once it finishes the previous merge, but in the event of a merge exception, the pending work is not resumed, but waitForMerges won't complete until all pending work is complete
> i worked around this by overriding doMerge() like so:
> {code}
>   protected final void doMerge(MergePolicy.OneMerge merge) throws IOException {
>     try {
>       super.doMerge(merge);
>     } catch (Throwable exc) {
>       // Just logging the exception and not rethrowing
>       // insert logging code here
>     }
>   }
> {code}
> Here's the rough steps i used to reproduce this issue:
> override doMerge like so
> {code}
>   protected final void doMerge(MergePolicy.OneMerge merge) throws IOException {
>     try {Thread.sleep(500L);} catch (InterruptedException e) { }
>     super.doMerge(merge);
>     throw new IOException("fail");
>   }
> {code}
> then, if you do the following:
> loop 50 times:
>   addDocument // any doc
>   commit
> waitForMerges // This will deadlock sometimes
> SOLR-2017 may be related to this (stack trace for deadlock looked related)

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