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From "Tim Smith (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1703) Add a waitForMerges() method to IndexWriter
Date Fri, 19 Jun 2009 19:34:07 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1703?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12721954#action_12721954
] 

Tim Smith commented on LUCENE-1703:
-----------------------------------

My primary use case for this is to stabilize an index prior to performing a backup operation

If background merges are ongoing, then partial segment files will be written to disk (potentially
while an rsync or other operation is running)

this will result in partial segments being backed up

while this should still be a viable index, as the partial segments have not been "committed",
it results in an unclean backup (this can result in rsync throwing warnings/errors (which
operations people greatly dislike)





> 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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