lang/java/reef-common/src/main/java/org/apache/reef/runtime/common/driver/evaluator/IdlenessCallbackEventHandler.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.reef.runtime.common.driver.evaluator;

import org.apache.reef.annotations.audience.DriverSide;
import org.apache.reef.annotations.audience.Private;
import org.apache.reef.runtime.common.driver.idle.EventHandlerIdlenessSource;
import org.apache.reef.wake.EventHandler;

/**
 * Checks for idleness after an {@link EventHandler#onNext(Object)} invocation.
 */
@Private
@DriverSide
final class IdlenessCallbackEventHandler<T> implements EventHandler<T> {
  private final EventHandler<T> innerHandler;
  private final EventHandlerIdlenessSource idlenessSource;

  IdlenessCallbackEventHandler(final EventHandler<T> innerHandler,
                               final EventHandlerIdlenessSource idlenessSource) {
    this.innerHandler = innerHandler;
    this.idlenessSource = idlenessSource;
  }

  /**
   * Checks idleness as a callback to the innerHandler.
   */
  @Override
  public void onNext(final T value) {
    innerHandler.onNext(value);
    idlenessSource.check();
  }
}