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https://issues.apache.org/jira/browse/LUCENE-1703?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12721938#action_12721938
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Tim Smith commented on LUCENE-1703:
-----------------------------------
I'm finding it a bit tricky to create a proper unit test for this
This is indirectly tested as IndexWriter.close() will call this method
but explicit calling of this method is harder to test as it requires
outstanding merges to be running (very difficult to trigger)
I started with TestIndexWriter.testNoWaitClose() as a base
however, modifying this to test waitForMerges() takes 11 seconds to run (surely
because it always waits, and doesn't abort the merges)
also, in order to properly test, another method should be added to IndexWriter
{code}
public synchronized int getOutstandingMerges() {
return mergingSegments.size();
}
{code}
I suppose the most proper test would create a subclass of
ConcurrentMergeScheduler that would block all merges until after i released a
lock. Then the test would add docs, fork off thread to unlock for merging in X
seconds, then call waitForMerges.
> Add a waitForMerges() method to IndexWriter
> -------------------------------------------
>
> Key: LUCENE-1703
> URL: https://issues.apache.org/jira/browse/LUCENE-1703
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Affects Versions: 2.4
> Reporter: Tim Smith
> Attachments: IndexWriter.java.diff
>
>
> It would be very useful to have a waitForMerges() method on the IndexWriter.
> Right now, the only way i can see to achieve this is to call
> IndexWriter.close()
> ideally, there would be a method on the IndexWriter to wait for merges
> without actually closing the index.
> This would make it so that background merges (or optimize) can be waited for
> without closing the IndexWriter, and then reopening a new IndexWriter
> the close() reopen IndexWriter method can be problematic if the close() fails
> as the write lock won't be released
> this could then result in the following sequence:
> * close() - fails
> * force unlock the write lock (per close() documentation)
> * new IndexWriter() (acquires write lock)
> * finalize() on old IndexWriter releases the write lock
> * Index is now not locked, and another IndexWriter pointing to the same
> directory could be opened
> If you don't force unlock the write lock, opening a new IndexWriter will fail
> until garbage collection calls finalize() the old IndexWriter
> If the waitForMerges() method is available, i would likely never need to
> close() the IndexWriter until right before the process being shutdown, so
> this issue would not occur (worst case scenario, the waitForMerges() fails)
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