Revert to FileDescriptor#sync from FileChannel.force to improve interrupt
resilienceb
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Key: DERBY-4963
URL: https://issues.apache.org/jira/browse/DERBY-4963
Project: Derby
Issue Type: Improvement
Reporter: Dag H. Wanvik
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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