flink-runtime/src/test/java/org/apache/flink/runtime/io/network/util/TestNotificationListener.java

/*
 * 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.flink.runtime.io.network.util;

import org.apache.flink.runtime.util.event.NotificationListener;

import java.util.concurrent.atomic.AtomicInteger;

/** A mock notification listener. */
public class TestNotificationListener implements NotificationListener {

    final AtomicInteger numberOfNotifications = new AtomicInteger();

    @Override
    public void onNotification() {
        synchronized (numberOfNotifications) {
            numberOfNotifications.incrementAndGet();

            numberOfNotifications.notifyAll();
        }
    }

    /**
     * Waits on a notification.
     *
     * <p><strong>Important</strong>: It's necessary to get the current number of notifications
     * <em>before</em> registering the listener. Otherwise the wait call may block indefinitely.
     *
     * <pre>
     * MockNotificationListener listener = new MockNotificationListener();
     *
     * int current = listener.getNumberOfNotifications();
     *
     * // Register the listener
     * register(listener);
     *
     * listener.waitForNotification(current);
     * </pre>
     */
    public void waitForNotification(int current) throws InterruptedException {
        synchronized (numberOfNotifications) {
            while (current == numberOfNotifications.get()) {
                numberOfNotifications.wait();
            }
        }
    }

    public int getNumberOfNotifications() {
        return numberOfNotifications.get();
    }

    public void reset() {
        numberOfNotifications.set(0);
    }
}