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/*
 * 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.iterative.task;

import org.apache.flink.api.common.aggregators.Aggregator;
import org.apache.flink.runtime.event.TaskEvent;
import org.apache.flink.runtime.iterative.event.WorkerDoneEvent;
import org.apache.flink.runtime.util.event.EventListener;
import org.apache.flink.types.Value;
import org.apache.flink.util.Preconditions;

import java.util.Map;

/**
 * Listener for {@link WorkerDoneEvent} which also aggregates all aggregators
 * from iteration tasks and signals the end of the superstep.
 */
public class SyncEventHandler implements EventListener {

	private final ClassLoader userCodeClassLoader;

	private final Map> aggregators;

	private final int numberOfEventsUntilEndOfSuperstep;

	private int workerDoneEventCounter;

	private boolean endOfSuperstep;

	public SyncEventHandler(int numberOfEventsUntilEndOfSuperstep, Map> aggregators, ClassLoader userCodeClassLoader) {
		Preconditions.checkArgument(numberOfEventsUntilEndOfSuperstep > 0);
		this.userCodeClassLoader = userCodeClassLoader;
		this.numberOfEventsUntilEndOfSuperstep = numberOfEventsUntilEndOfSuperstep;
		this.aggregators = aggregators;
	}

	@Override
	public void onEvent(TaskEvent event) {
		if (WorkerDoneEvent.class.equals(event.getClass())) {
			onWorkerDoneEvent((WorkerDoneEvent) event);
			return;
		}
		throw new IllegalStateException("Unable to handle event " + event.getClass().getName());
	}

	private void onWorkerDoneEvent(WorkerDoneEvent workerDoneEvent) {
		if (this.endOfSuperstep) {
			throw new RuntimeException("Encountered WorderDoneEvent when still in End-of-Superstep status.");
		}

		workerDoneEventCounter++;

		String[] aggNames = workerDoneEvent.getAggregatorNames();
		Value[] aggregates = workerDoneEvent.getAggregates(userCodeClassLoader);

		if (aggNames.length != aggregates.length) {
			throw new RuntimeException("Inconsistent WorkerDoneEvent received!");
		}

		for (int i = 0; i < aggNames.length; i++) {
			@SuppressWarnings("unchecked")
			Aggregator aggregator = (Aggregator) this.aggregators.get(aggNames[i]);
			aggregator.aggregate(aggregates[i]);
		}

		if (workerDoneEventCounter % numberOfEventsUntilEndOfSuperstep == 0) {
			endOfSuperstep = true;
			Thread.currentThread().interrupt();
		}
	}

	public boolean isEndOfSuperstep() {
		return this.endOfSuperstep;
	}

	public void resetEndOfSuperstep() {
		this.endOfSuperstep = false;
	}
}