/*
* 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.geode.internal.cache;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
/**
* A lock used for the backup process. This is a reentrant lock that provides a "backup" mode, where
* the lock is held by a "backup thread" which can be assigned later than the time we lock.
*
* We need this because our backup process is two phase. In the first phase we aquire the lock and
* in the second phase we actually do the backup. During the second phase we need to reenter the
* lock and release it with a different thread.
*
*/
public class BackupLock extends ReentrantLock {
private Thread backupThread;
boolean isBackingUp;
Condition backupDone = super.newCondition();
public void lockForBackup() {
super.lock();
isBackingUp = true;
super.unlock();
}
public void setBackupThread(Thread thread) {
super.lock();
backupThread = thread;
super.unlock();
}
public void unlockForBackup() {
super.lock();
isBackingUp = false;
backupThread = null;
backupDone.signalAll();
super.unlock();
}
/**
* Acquire this lock, waiting for an in progress backup if one is in progress.
*/
@Override
public void lock() {
lock(true);
}
/**
* Acquire this lock, Optionally waiting for a backup to finish the first phase. Any operations
* that update metadata related to the distributed system state should pass true for this flag,
* because we need to make sure we get a point in time snapshot of the init files across members
* to for metadata consistentency.
*
* Updates which update only record changes to the local state on this member(eg, switching
* oplogs), do not need to wait for the backup.
*
* @param waitForBackup if true, we will wait for an in progress backup before acquiring this
* lock.
*/
public void lock(boolean waitForBackup) {
super.lock();
while (isBackingUp && waitForBackup && !(Thread.currentThread() == backupThread)) {
backupDone.awaitUninterruptibly();
}
}
}