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From "Shai Erera (JIRA)" <j...@apache.org>
Subject [jira] Resolved: (LUCENE-2592) Add static readSnapshotsInfo to PersistentSnapshotDeletionPolicy
Date Sat, 21 Aug 2010 19:21:15 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-2592?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Shai Erera resolved LUCENE-2592.
--------------------------------

    Resolution: Fixed

Committed revision 987811 (3x).
Committed revision 987814 (trunk).

> Add static readSnapshotsInfo to PersistentSnapshotDeletionPolicy
> ----------------------------------------------------------------
>
>                 Key: LUCENE-2592
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2592
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Shai Erera
>            Assignee: Shai Erera
>            Priority: Minor
>             Fix For: 3.1, 4.0
>
>         Attachments: LUCENE-2592.patch
>
>
> PSDP persists the snapshots information in a Directory. When you open PSDP, it obtains
a write lock on the snapshots dir (by keeping an open IndexWriter), and updates the directory
when snapshots are created/released.
> This causes problem in the following scenario -- you have two processes, one updates
the 'content' index and keeps PSDP open (because it also takes snapshots). Another process
wants to read the existing snapshots information and open a read-only IndexReader on the 'content'
index. The other process cannot read the existing snapshots information, because p1 keeps
a write lock on the snapshots directory.
> There are two possible solutions:
> # Have PSDP open the IndexWriter over the directory for each snapshot/release. A bit
expensive, and unnecessary.
> # Introduce a static readSnapshotsInfo on PSDP which accepts a Directory and returns
the snapshots information. IMO it's cleaner, and won't have the performance overhead of opening/closing
the IW as before.
> I'll post a patch (implementing the 2nd approach) shortly. I'd appreciate any comments.

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