/*
* 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.util;
import java.io.InterruptedIOException;
import java.util.concurrent.Callable;
/**
* This class serializes execution of concurrent tasks. This is useful when we want only one thread
* to perform an expensive operation such that if the operation fails, all other threads fail with
* the same exception without having to perform the expensive operation.
*
*
* @param <T> the type of return value
*/
public class SingletonCallable<T> {
private Object lock = new Object();
private volatile boolean running = false;
private Exception ex = null;
public T runSerially(Callable<T> c) throws Exception {
T retval = null;
synchronized (lock) {
while (running) {
try {
lock.wait();
if (ex != null) {
throw ex;
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new InterruptedIOException();
}
}
ex = null;
running = true;
}
Exception exception = null;
try {
retval = c.call();
} catch (Exception e) {
exception = e;
} finally {
synchronized (lock) {
if (exception != null && !ignoreException(exception)) {
ex = exception;
}
running = false;
lock.notifyAll();
}
}
if (exception != null) {
throw exception;
}
return retval;
}
/**
* Override this method for handling exception encountered while running the Callable c.
*
* @return false if we want the waiting threads to fail immediately<br/>
* true if we want the waiting threads to invoke the callable
*
*/
public boolean ignoreException(Exception e) {
return false;
}
}