org.apache.flink.util

Class ResourceGuard

java.lang.Object

org.apache.flink.util.ResourceGuard

All Implemented Interfaces:

Serializable, AutoCloseable

public class ResourceGuard
extends Object
implements AutoCloseable, Serializable

This class is a guard for shared resources with the following invariants. The resource can be acquired by multiple clients in parallel through the acquireResource() call. As a result of the call, each client gets a ResourceGuard.Lease. The close() method of the lease releases the resources and reduces the client count in the ResourceGuard object. The protected resource should only be disposed once the corresponding resource guard is successfully closed, but the guard can only be closed once all clients that acquired a lease for the guarded resource have released it. Before this is happened, the call to close() will block until the zero-open-leases condition is triggered. After the resource guard is closed, calls to acquireResource() will fail with exception. Notice that, obviously clients are responsible to release the resource after usage. All clients are considered equal, i.e. there is only a global count maintained how many times the resource was acquired but not by whom.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	ResourceGuard.Lease A lease is issued by the ResourceGuard as result of calls to acquireResource().

Constructor Summary

Constructors

Constructor and Description
ResourceGuard()

Method Summary

Modifier and Type	Method and Description
ResourceGuard.Lease	acquireResource() Acquired access from one new client for the guarded resource.
void	close() Closed the resource guard.
int	getLeaseCount() Returns the current count of open leases.
boolean	isClosed() Returns true if the resource guard is closed, i.e.

Methods inherited from class java.lang.Object

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

Constructor Detail

ResourceGuard

public ResourceGuard()

Method Detail

acquireResource

public ResourceGuard.Lease acquireResource()
                                    throws IOException

Acquired access from one new client for the guarded resource.

Throws:

IOException - when the resource guard is already closed.

close

public void close()

Closed the resource guard. This method will block until all calls to acquireResource() have seen their matching call to releaseResource().

Specified by:

close in interface AutoCloseable

isClosed

public boolean isClosed()

Returns true if the resource guard is closed, i.e. after close() was called.

getLeaseCount

public int getLeaseCount()

Returns the current count of open leases.