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From "Marcel Reutegger (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-204) Improve recoverability
Date Fri, 16 Feb 2007 08:38:05 GMT

    [ https://issues.apache.org/jira/browse/JCR-204?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12473642
] 

Marcel Reutegger commented on JCR-204:
--------------------------------------

No, the index is always updated after the persistence manager successfully committed the transaction.
It may happen though that a query selects a node that still exists in the persistence manager
but is deleted in your session or un-committed transaction.

> Improve recoverability
> ----------------------
>
>                 Key: JCR-204
>                 URL: https://issues.apache.org/jira/browse/JCR-204
>             Project: Jackrabbit
>          Issue Type: Improvement
>          Components: core, indexing, observation, transactions
>         Environment: svn revision: 265028
>            Reporter: Marcel Reutegger
>         Assigned To: Marcel Reutegger
>            Priority: Minor
>
> Transactions in Jackrabbit are committed in SharedItemStateManager.store(). While the
call to PersistenceManager.store() is by its definition atomic, updates on the index through
synchronous notification by the ObservationManager are not. Consequently, it may happen that
the index is not up-to-date with the workspace data in case of a crash.
> Consider the following cases:
> 1)
> - changes in a ChangeLog are successfully stored by the persistence manager
> - the observation manager notifies the query handler about the change
> - the query handler starts to update the index
> - system crashes
> -> the index is missing some changes
> 2)
> - changes in a ChangeLog are successfully stored by the persistence manager
> - system crashes
> -> the index is missing all changes
> To prevent situations like 1) the index must be fully transactional implementing ACID
properties.
> In case an index update cannot be completed, the index will appear as if the update never
happened. Which results in a situation described in example 2)
> To prevent situations like 2) the observation manager musts keep track of transactions
and make sure that committed transactions (the ones that successfully stored the changes in
the persistence manager) successfully notify all listeners. If the system should crash while
listeners are notified the events must be re-delivered on restart.
> comments and suggestions on alternatives are welcome!

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