[jira] Resolved: (DERBY-4963) Revert to FileDescriptor#sync from FileChannel#force to improve interrupt resilience

["Dag H. Wanvik (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DERBY-4963?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dag H. Wanvik resolved DERBY-4963.
----------------------------------

          Resolution: Fixed
    Issue & fix info: [Release Note Needed]  (was: [Release Note Needed, Patch Available])

Committed as svn 1057702, resolving. WIll keep it open till I have produced a release note.

> Revert to FileDescriptor#sync from FileChannel#force to improve interrupt resilience
> ------------------------------------------------------------------------------------
>
>                 Key: DERBY-4963
>                 URL: https://issues.apache.org/jira/browse/DERBY-4963
>             Project: Derby
>          Issue Type: Improvement
>          Components: Store
>            Reporter: Dag H. Wanvik
>            Assignee: Dag H. Wanvik
>             Fix For: 10.8.0.0
>
>         Attachments: derby-4963-1.diff, derby-4963-1.stat
>
>
> FileChannel.force is interruptable, and we really don't want to be interrupted when we flush the log file.  Happily, on most platforms, we use the "rws"/"rwd" file open mask which makes the writes thjemselves synchronized, so no subsequent explicit file level sync is needed anyway.
> DirFile4#getRandowmAccessFile should use plain DirRandomAccessFile instead of the current DirRandomAccessFile4. This will make StorageRandomAccessFile#sync map to FileDescriptor#sync instead of FileChannel#force (also for NIO supporting platforms). 
> Since FileDescriptor#sync does not allow synching file data only (it also synchronizes metadata), those platforms which do not support write synchronization will experience a performance drop, but this is the price we have to pay to survive interrupts without shutting down the database on those platforms. 
> Users which experience this as a problem, should update to a newer JVM which does support "rws"/"rwd" in the mode argument to java.io.RandomAccessFile (http://download.oracle.com/javase/6/docs/api/java/io/RandomAccessFile.html#RandomAccessFile(java.io.File,%20java.lang.String).
> Cf. also discussion on https://issues.apache.org/jira/browse/DERBY-4741?focusedCommentId=12977862&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12977862 .

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