net.sf.farrago.util
Class FarragoFileLockAllocation

java.lang.Object
  net.sf.farrago.util.FarragoFileLockAllocation

All Implemented Interfaces:

FarragoAllocation, ClosableAllocation

public class FarragoFileLockAllocation
extends Object
implements FarragoAllocation

FarragoFileLockAllocation takes care of unlocking a file when it is closed.

Version:

$Id: //open/dev/farrago/src/net/sf/farrago/util/FarragoFileLockAllocation.java#16 $

Author:

John V. Sichi

Field Summary

private FileChannel	channel
private File	file
private FileLock	lock
private static int	LOCK_OFFSET Location to lock.
private RandomAccessFile	randomAccessFile
private static Logger	tracer

Constructor Summary

FarragoFileLockAllocation(FarragoAllocationOwner owner, File file, boolean tryLock)
Creates a new FarragoFileLockAllocation by locking a file.

Method Summary

void	closeAllocation() Closes this object.
static void	main(String[] args) Command-line entry point for bench testing.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

LOCK_OFFSET

private static final int LOCK_OFFSET

Location to lock. We lock a bogus byte way beyond any real data to make sure the lock doesn't interfere with I/O on operating systems with non-advisory lock semantics such as Windows. Don't use Long.MAX_VALUE because that breaks on any OS without large file support.

See Also:

Constant Field Values

tracer

private static final Logger tracer

file

private File file

randomAccessFile

private RandomAccessFile randomAccessFile

channel

private FileChannel channel

lock

private FileLock lock

Constructor Detail

FarragoFileLockAllocation

public FarragoFileLockAllocation(FarragoAllocationOwner owner,
                                 File file,
                                 boolean tryLock)
                          throws IOException

Creates a new FarragoFileLockAllocation by locking a file.

Parameters:

owner - the FarragoAllocationOwner which will be made responsible for the lock as a result of this call

file - the file to be locked for the lifetime of this allocation; if it does not exist, it will be created (but not deleted) automatically

tryLock - if true and lock cannot be obtained throw an exception; if false, wait for the lock instead

Throws:

IOException - if lock attempt failed

Method Detail

closeAllocation

public void closeAllocation()

Description copied from interface: ClosableAllocation

Closes this object.

Specified by:

closeAllocation in interface ClosableAllocation

main

public static void main(String[] args)
                 throws Exception

Command-line entry point for bench testing. Attempts to lock the file named by the one and only argument and hold the lock for 20 seconds.

TODO jvs 24-Aug-2005: Figure out a way to test this automatically. Requires starting two concurrent processes.

Parameters:

args - args[0] = name of file to lock

Throws:

Exception