/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.oozie.service;
import org.apache.oozie.util.Instrumentable;
import org.apache.oozie.util.Instrumentation;
import org.apache.oozie.lock.LockToken;
import org.apache.oozie.lock.MemoryLocks;
/**
* Service that provides in-memory locks. Assumes no other Oozie servers are using the database.
*/
public class MemoryLocksService implements Service, Instrumentable {
protected static final String INSTRUMENTATION_GROUP = "locks";
private MemoryLocks locks;
/**
* Initialize the memory locks service
*
* @param services services instance.
*/
@Override
public void init(Services services) throws ServiceException {
locks = new MemoryLocks();
}
/**
* Destroy the memory locks service.
*/
@Override
public void destroy() {
locks = null;
}
/**
* Return the public interface for the memory locks services
*
* @return {@link MemoryLocksService}.
*/
@Override
public Class<? extends Service> getInterface() {
return MemoryLocksService.class;
}
/**
* Instruments the memory locks service.
*
* @param instr instance to instrument the memory locks service to.
*/
public void instrument(Instrumentation instr) {
final MemoryLocks finalLocks = this.locks;
instr.addVariable(INSTRUMENTATION_GROUP, "locks", new Instrumentation.Variable<Long>() {
public Long getValue() {
return (long) finalLocks.size();
}
});
}
/**
* Obtain a READ lock for a source.
*
* @param resource resource name.
* @param wait time out in milliseconds to wait for the lock, -1 means no timeout and 0 no wait.
* @return the lock token for the resource, or <code>null</code> if the lock could not be obtained.
* @throws InterruptedException thrown if the thread was interrupted while waiting.
*/
public LockToken getReadLock(String resource, long wait) throws InterruptedException {
return locks.getReadLock(resource, wait);
}
/**
* Obtain a WRITE lock for a source.
*
* @param resource resource name.
* @param wait time out in milliseconds to wait for the lock, -1 means no timeout and 0 no wait.
* @return the lock token for the resource, or <code>null</code> if the lock could not be obtained.
* @throws InterruptedException thrown if the thread was interrupted while waiting.
*/
public LockToken getWriteLock(String resource, long wait) throws InterruptedException {
return locks.getWriteLock(resource, wait);
}
}