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From "Marcel Reutegger (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-314) Fine grained locking in SharedItemStateManager
Date Wed, 23 May 2007 13:23:16 GMT

    [ https://issues.apache.org/jira/browse/JCR-314?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12498226
] 

Marcel Reutegger commented on JCR-314:
--------------------------------------

Applied the patches ISMLocking.patch and FineGrainedISMLocking-v2.patch with one slight change:
the SISM used the default implementation for now.

Committed in revision: 540944

There are some remaining issues before we can use FineGrainedISMLocking:

- using FineGrainedISMLocking allows for concurrent access to item state caches, which were
not possible before. We must ensure that all item state caches are prepared for that.
- do extensive testing
- we should check again if the performance is ok

> Fine grained locking in SharedItemStateManager
> ----------------------------------------------
>
>                 Key: JCR-314
>                 URL: https://issues.apache.org/jira/browse/JCR-314
>             Project: Jackrabbit
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 0.9, 1.0, 1.0.1, 1.1, 1.1.1, 1.2.1, 1.2.2, 1.2.3
>            Reporter: Marcel Reutegger
>         Attachments: FineGrainedISMLocking-v2.patch, FineGrainedISMLocking.patch, ISMLocking.patch
>
>
> The SharedItemStateManager (SISM) currently uses a simple read-write lock to ensure data
consistency. Store operations to the PersistenceManager (PM) are effectively serialized.
> We should think about more sophisticated locking to allow concurrent writes on the PM.
> One possible approach:
> If a transaction is currently storing data in a PM a second transaction may check if
the set of changes does not intersect with the first transaction. If that is the case it can
safely store its data in the PM.
> This fine grained locking must also be respected when reading from the SISM. A read request
for an item that is currently being stored must be blocked until the store is finished.

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