CC'ing java-dev to talk about details of locking. I can reproduce this on Windows XP, Java 1.4.2: two separate JVMs are able to get the Lock at the same time.
The code looks correct to me. Strangely, if I make a separate standalone test that just uses java.io.File.createNewFile directly, it works correctly (this is what FSDirectory.makeLock uses). If I hardwire the lock filename inside FSDirectory.makeLock, it also fails, unless I use a very short filename, then it seems to work. Something intermittent is going on. Then in looking at the docs for java.io.File.createNewfile(): http://java.sun.com/j2se/1.5.0/docs/api/java/io/File.html#createNewFile() There is this spooky comment: Note: this method should not be used for file-locking, as the resulting protocol cannot be made to work reliably. The FileLock facility should be used instead. Finally, it looks like Hadoop's LocalFileSystem class is already using FileLock's. One benefit of FileLocks is if JVM crashes, the OS should handle removing the lock correctly. I know this has been an issue in the past with "commit lock timeout" errors due to the lock file remaining in the filesystem, with the current approach. Does anyone know of any reasons not to switch Lucene's FSDirectory locking to the java.nio.channels.FileLock? EG, are there any performance issues that people are aware of? It's available since Java 1.4. Mike jm <[EMAIL PROTECTED]> 06/20/2006 01:19 PM Please respond to java-user@lucene.apache.org To java-user@lucene.apache.org cc Subject using lucene Lock inter-jvm Hi, I am trying to peruse lucene's Lock for my own purposes, I need to lock several java processes and I thought I could reuse the Lock stuff. I understand lucene locks work across jvm. But I cannot make it work. I tried to reproduce my problem in a small class: public class SysLock { private static final Logger logger = Logger.getLogger(SysLock.class); private int id; public SysLock(int i) { id = i; } // public static void main(String[] args) throws Exception { // System.setProperty("org.apache.lucene.lockDir", "C:\\temp\\todel"); // SysLock l1 = new SysLock(1); // SysLock l2 = new SysLock(2); // // TransferThread t = l1.new TransferThread(l1); // t.start(); // TransferThread t2 = l2.new TransferThread(l2); // t2.start(); // // logger.info("Finished."); // } public static void main(String[] args) throws Exception { System.setProperty("org.apache.lucene.lockDir", "C:\\temp\\todel"); SysLock l1 = new SysLock(new Date().getSeconds()); TransferThread t = l1.new TransferThread(l1); t.start(); logger.info("Finished."); } private void forever() throws IOException { FSDirectory directory = FSDirectory.getDirectory("C:\\temp\\a", true); try { new Lock.With(directory.makeLock("COMMIT_LOCK_NAME"), COMMIT_LOCK_TIMEOUT) { public Object doBody() throws IOException { while (true) { System.out.println("i'm " + id); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } } } }.run(); } catch (Exception e) { System.out.println(id + " could not get lock"); } } class TransferThread extends Thread { public TransferThread(SysLock sl) { this.sl = sl; } public void run() { try { sl.forever(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } private SysLock sl; } } When I run the main() that is commented (that is, the lock works with two threads in the same jvm) it works ok, the second TransferThread cannot get the lock. But when I run the uncommented main() twice, both processes adquire a lock, even if only one lock file exists in the lockdir. Something I am missing probably.... Many thanks javi --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
