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From "Yonik Seeley (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-2565) Prevent IW#close and cut over to IW#commit
Date Tue, 09 Aug 2011 17:25:27 GMT

    [ https://issues.apache.org/jira/browse/SOLR-2565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13081775#comment-13081775
] 

Yonik Seeley commented on SOLR-2565:
------------------------------------

I think the removal of all of the synchronization in the update handler leads to a race condition
on reopen.

Basically, the order that we start a reopen in different threads does not have to correspond
to the order that the reopen finishes, or the order that the new searcher is registered. 
This can mean temporarily lost documents - a request can add a document + repoen and due to
scheduling have an older reopen registered last in a different thread (meaning the document
won't be visible).

So it looks like we need to synchronize to ensure that only one thread reopens at a time.

As far as I can tell, I don't think that this synchronization needs to extend to the IW.commit()
for a hard commit. 

> Prevent IW#close and cut over to IW#commit
> ------------------------------------------
>
>                 Key: SOLR-2565
>                 URL: https://issues.apache.org/jira/browse/SOLR-2565
>             Project: Solr
>          Issue Type: Improvement
>          Components: update
>    Affects Versions: 4.0
>            Reporter: Simon Willnauer
>            Assignee: Mark Miller
>             Fix For: 4.0
>
>         Attachments: SOLR-2565.patch
>
>
> Spinnoff from SOLR-2193. We already have a branch to work on this issue here https://svn.apache.org/repos/asf/lucene/dev/branches/solr2193

> The main goal here is to prevent solr from closing the IW and use IW#commit instead.
AFAIK the main issues here are:
> The update handler needs an overhaul.
> A few goals I think we might want to look at:
> 1. Expose the SolrIndexWriter in the api or add the proper abstractions to get done what
we now do with special casing:
> 2. Stop closing the IndexWriter and start using commit (still lazy IW init though).
> 3. Drop iwAccess, iwCommit locks and sync mostly at the Lucene level.
> 4. Address the current issues we face because multiple original/'reloaded' cores can
have a different IndexWriter on the same index.
> Eventually this is a preparation for NRT support in Solr which I will create a followup
issue for.

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