com.gemstone.gemfire.internal.cache.BackupLock Maven / Gradle / Ivy
/*
* Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
*
* Licensed 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. See accompanying
* LICENSE file.
*/
package com.gemstone.gemfire.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.
* @author dsmith
*
*/
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();
}
}
}