net.openhft.chronicle.bytes.domestic

Class ReentrantFileLock

java.lang.Object

java.nio.channels.FileLock

net.openhft.chronicle.bytes.domestic.ReentrantFileLock

All Implemented Interfaces:

AutoCloseable

public final class ReentrantFileLock
extends FileLock

A way of acquiring exclusive locks on files in a re-entrant fashion.

It will prevent a single thread that uses the static lock(File, FileChannel) or tryLock(File, FileChannel) methods to acquire locks from causing an OverlappingFileLockException. Separate threads will not be prevented from taking overlapping file locks.

All the usual caveats around file locks apply, shared locks and locks for specific ranges are not supported. See domestic-overview.adoc for usage notes.

Constructor Summary

Constructors

Constructor and Description
ReentrantFileLock(String canonicalPath, FileLock fileLock) Constructs a ReentrantFileLock.

Method Summary

Modifier and Type	Method and Description
Channel	acquiredBy()
static boolean	isHeldByCurrentThread(File file) Is there a cached FileLock held by the current thread for the specified file
boolean	isValid()
static ReentrantFileLock	lock(File file, FileChannel fileChannel) Take an exclusive lock on the entire file, blocks until lock is acquired
void	release() Releases the lock.
static @Nullable ReentrantFileLock	tryLock(File file, FileChannel fileChannel) Try and take an exclusive lock on the entire file, non-blocking

Methods inherited from class java.nio.channels.FileLock

channel, close, isShared, overlaps, position, size, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

ReentrantFileLock

public ReentrantFileLock(String canonicalPath,
                         FileLock fileLock)

Constructs a ReentrantFileLock.

Parameters:

canonicalPath - The canonical path of the file to be locked.

fileLock - The delegate FileLock.

Method Detail

acquiredBy

public Channel acquiredBy()

Ensures that only the owning thread accesses the delegate FileLock.

Overrides:

acquiredBy in class FileLock

isValid

public boolean isValid()

Ensures that only the owning thread accesses the delegate FileLock.

Specified by:

isValid in class FileLock

release

public void release()
             throws IOException

Releases the lock. Decrements the re-entrance counter and only releases the underlying file lock when the counter reaches zero.

Specified by:

release in class FileLock

Throws:

IOException - If an I/O error occurs.

tryLock

@Nullable
public static @Nullable ReentrantFileLock tryLock(File file,
                                                            FileChannel fileChannel)
                                                     throws IOException

Try and take an exclusive lock on the entire file, non-blocking

Parameters:

file - The file to lock

fileChannel - An open to the file

Returns:

the lock if it was acquired, or null if it could not be acquired

Throws:

IOException - If an I/O error occurs.

lock

public static ReentrantFileLock lock(File file,
                                     FileChannel fileChannel)
                              throws IOException

Take an exclusive lock on the entire file, blocks until lock is acquired

Parameters:

file - The file to lock

fileChannel - An open to the file

Returns:

the lock if it was acquired, or null if it could not be acquired

Throws:

IOException - If an I/O error occurs.

isHeldByCurrentThread

public static boolean isHeldByCurrentThread(File file)

Is there a cached FileLock held by the current thread for the specified file

Parameters:

file - The file to check

Returns:

true if there is a cached file lock, false otherwise