/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package com.bigdata.btree;
import java.util.concurrent.locks.Lock;
/**
* Interface for managing read/write locks on persistence capable data
* structures.
*
* @see <a href="http://trac.blazegraph.com/ticket/855"> AssertionError: Child does
* not have persistent identity </a>
*/
public interface IReadWriteLockManager {
/**
* Return a {@link Lock} that may be used to obtain a shared read lock which
* is used (in the absence of other concurrency control mechanisms) to
* permit concurrent readers on an unisolated index while serializing access
* to that index when a writer must run. This is exposed for processes which
* need to obtain the write lock to coordinate external operations.
* <p>
* Note: If the persistence capable data structure is read-only then the
* returned {@link Lock} is a singleton that ignores all lock requests. This
* is because our read-only persistence capable data structures are already
* thread-safe for concurrent readers.
*
* @return The lock.
*/
Lock readLock();
/**
* Return a {@link Lock} that may be used to obtain an exclusive write lock
* which is used (in the absence of other concurrency control mechanisms) to
* serialize all processes accessing an unisolated index when a writer must
* run. This is exposed for processes which need to obtain the write lock to
* coordinate external operations.
*
* @return The lock.
*
* @throws UnsupportedOperationException
* unless the view supports mutation.
*/
Lock writeLock();
/**
* Return the #of read-locks held by the current thread for a mutable index
* view.
*
* @return The #of reentrant read locks held by the current thread -or- ZERO
* if the index is read-only (read locks are not tracked for a
* read-only index view).
*/
int getReadLockCount();
/**
* Return <code>true</code> iff the data structure is read-only.
*/
boolean isReadOnly();
}