Problem with FileLock
- From: alejandrina <apattin@xxxxxxxxx>
- Date: Fri, 13 Jul 2007 14:34:14 -0700
Hi experts,
We need to update a file (on a file server) from many different
machines. To synchromize the updates I am using FileLock.
Everything works as advertised (ie if a machine gets the lock,
it writes to the file while the other machines wait, everything is
written in the proper order). The same test, using Linux machines,
fails: the file is clobbered (meaning one update gets on top of
another). No Exceptions are thrown; in fact the debug statements
indicate that all the machines are acquiring the exclusive lock)
Anyone can shed light? Here is the critical method with some
debug statements:
public void write (String s) throws Exception {
ByteBuffer bb = stringToByteBuffer(s);
//lock the file and wait till we can
FileChannel channel = fos.getChannel();
FileLock lock = null;
try {
while ((lock = channel.tryLock()) == null) {
System.out.println (Utils.getHostname() + " Failed lock...wait");
Thread.sleep(100);
}
System.out.println (Utils.getHostname() + " Locked:" + lock);
System.out.println (Utils.getHostname() + " Lock type is "+
((lock.isShared())?"shared":"exclusive"));
System.out.println (Utils.getHostname() + " Is lock valid: " +
lock.isValid());
//write the title first if noone's done it
//and they asked for one
if (channel.size() <= 0 && bbTitle != null)
channel.write (bbTitle);
channel.write(bb);
} catch (Exception e) {
throw (e);
} finally {
if (lock != null) {
System.out.println (Utils.getHostname() + " Releasing lock");
lock.release();
}
}
}
.
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