Package org.infinispan.commons.util.concurrent

Class FileSystemLock

java.lang.Object

org.infinispan.commons.util.concurrent.FileSystemLock

@ThreadSafe
public class FileSystemLock
extends Object

A simplified global lock backed by the file system.

This implementation allows to control the access to external resource between different virtual machines. A file is created to control access, where subsequent tries do not succeed acquiring the lock as long as the file exists.

Warning: This implementation does not have the semantics of a traditional Lock. Does not provide memory or visibility guarantees following the JMM.

Since:

15.0

Constructor Summary

Constructors

Constructor	Description
FileSystemLock(Path directory, String name)	Creates new instance of the lock.

Method Summary

Modifier and Type	Method	Description
boolean	isAcquired()	Check whether the current instance holds the global lock.
String	toString()
boolean	tryLock()	Tries to acquire the global lock.
void	unlock()	Unlocks the current instance if holding the global lock.
void	unsafeLock()	Unsafely forces the current instance to hold the lock.

Methods inherited from class java.lang.Object

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

Constructor Details

FileSystemLock

public FileSystemLock(Path directory,
 String name)

Creates new instance of the lock.

Creates a new file in the provided directory utilizing the lock's name.

Parameters:

directory - : Root directory to create the lock files.

name - : Uniquely identify the file name. If the names conflict, it means the lock is already held.

Method Details

tryLock

public boolean tryLock()
                throws IOException

Tries to acquire the global lock.

Creates a file in the provided directory with the lock's name. If the file already exists, the lock is held by another instance. The instance is not necessarily in the same virtual machine.

Returns:

true if acquired the lock, false, otherwise.

Throws:

IOException

See Also:

• Check the thrown exceptions.

unlock

public void unlock()

Unlocks the current instance if holding the global lock.

This method only has an effect if the lock is hold by this instance. Effectively, the underlying file is deleted.

unsafeLock

public void unsafeLock()
                throws IOException

Unsafely forces the current instance to hold the lock.

This method bypasses the existing lock mechanism to delete the underlying file and acquire ownership over it. Use this method with caution! This method is useful in cases of hard crashes of the virtual machine where the lock was not released prior to shutdown.

Throws:

IOException

See Also:

• Exceptions list.

isAcquired

public boolean isAcquired()

Check whether the current instance holds the global lock.

Returns:

true in case the lock is held, false, otherwise.

toString

public String toString()

Overrides:

toString in class Object