/*
* 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 java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.flink.runtime.event.TaskEvent;
import org.apache.flink.runtime.operators.BatchTask;
import org.apache.flink.types.IntValue;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.flink.api.common.aggregators.Aggregator;
import org.apache.flink.api.common.aggregators.AggregatorWithName;
import org.apache.flink.api.common.aggregators.ConvergenceCriterion;
import org.apache.flink.runtime.io.network.api.reader.MutableRecordReader;
import org.apache.flink.runtime.iterative.event.AllWorkersDoneEvent;
import org.apache.flink.runtime.iterative.event.TerminationEvent;
import org.apache.flink.runtime.iterative.event.WorkerDoneEvent;
import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
import org.apache.flink.runtime.operators.util.TaskConfig;
import org.apache.flink.types.Value;
import org.apache.flink.util.Preconditions;
/**
* The task responsible for synchronizing all iteration heads, implemented as an output task. This task
* will never see any data.
* In each superstep, it simply waits until it has received a {@link WorkerDoneEvent} from each head and will send back
* an {@link AllWorkersDoneEvent} to signal that the next superstep can begin.
*/
public class IterationSynchronizationSinkTask extends AbstractInvokable implements Terminable {
private static final Logger log = LoggerFactory.getLogger(IterationSynchronizationSinkTask.class);
private MutableRecordReader<IntValue> headEventReader;
private SyncEventHandler eventHandler;
private ConvergenceCriterion<Value> convergenceCriterion;
private ConvergenceCriterion<Value> implicitConvergenceCriterion;
private Map<String, Aggregator<?>> aggregators;
private String convergenceAggregatorName;
private String implicitConvergenceAggregatorName;
private int currentIteration = 1;
private int maxNumberOfIterations;
private final AtomicBoolean terminated = new AtomicBoolean(false);
// --------------------------------------------------------------------------------------------
@Override
public void invoke() throws Exception {
this.headEventReader = new MutableRecordReader<>(
getEnvironment().getInputGate(0),
getEnvironment().getTaskManagerInfo().getTmpDirectories());
TaskConfig taskConfig = new TaskConfig(getTaskConfiguration());
// store all aggregators
this.aggregators = new HashMap<>();
for (AggregatorWithName<?> aggWithName : taskConfig.getIterationAggregators(getUserCodeClassLoader())) {
aggregators.put(aggWithName.getName(), aggWithName.getAggregator());
}
// store the aggregator convergence criterion
if (taskConfig.usesConvergenceCriterion()) {
convergenceCriterion = taskConfig.getConvergenceCriterion(getUserCodeClassLoader());
convergenceAggregatorName = taskConfig.getConvergenceCriterionAggregatorName();
Preconditions.checkNotNull(convergenceAggregatorName);
}
// store the default aggregator convergence criterion
if (taskConfig.usesImplicitConvergenceCriterion()) {
implicitConvergenceCriterion = taskConfig.getImplicitConvergenceCriterion(getUserCodeClassLoader());
implicitConvergenceAggregatorName = taskConfig.getImplicitConvergenceCriterionAggregatorName();
Preconditions.checkNotNull(implicitConvergenceAggregatorName);
}
maxNumberOfIterations = taskConfig.getNumberOfIterations();
// set up the event handler
int numEventsTillEndOfSuperstep = taskConfig.getNumberOfEventsUntilInterruptInIterativeGate(0);
eventHandler = new SyncEventHandler(numEventsTillEndOfSuperstep, aggregators,
getEnvironment().getUserClassLoader());
headEventReader.registerTaskEventListener(eventHandler, WorkerDoneEvent.class);
IntValue dummy = new IntValue();
while (!terminationRequested()) {
if (log.isInfoEnabled()) {
log.info(formatLogString("starting iteration [" + currentIteration + "]"));
}
// this call listens for events until the end-of-superstep is reached
readHeadEventChannel(dummy);
if (log.isInfoEnabled()) {
log.info(formatLogString("finishing iteration [" + currentIteration + "]"));
}
if (checkForConvergence()) {
if (log.isInfoEnabled()) {
log.info(formatLogString("signaling that all workers are to terminate in iteration ["
+ currentIteration + "]"));
}
requestTermination();
sendToAllWorkers(new TerminationEvent());
} else {
if (log.isInfoEnabled()) {
log.info(formatLogString("signaling that all workers are done in iteration [" + currentIteration
+ "]"));
}
AllWorkersDoneEvent allWorkersDoneEvent = new AllWorkersDoneEvent(aggregators);
sendToAllWorkers(allWorkersDoneEvent);
// reset all aggregators
for (Aggregator<?> agg : aggregators.values()) {
agg.reset();
}
currentIteration++;
}
}
}
private boolean checkForConvergence() {
if (maxNumberOfIterations == currentIteration) {
if (log.isInfoEnabled()) {
log.info(formatLogString("maximum number of iterations [" + currentIteration
+ "] reached, terminating..."));
}
return true;
}
if (convergenceAggregatorName != null) {
@SuppressWarnings("unchecked")
Aggregator<Value> aggregator = (Aggregator<Value>) aggregators.get(convergenceAggregatorName);
if (aggregator == null) {
throw new RuntimeException("Error: Aggregator for convergence criterion was null.");
}
Value aggregate = aggregator.getAggregate();
if (convergenceCriterion.isConverged(currentIteration, aggregate)) {
if (log.isInfoEnabled()) {
log.info(formatLogString("convergence reached after [" + currentIteration
+ "] iterations, terminating..."));
}
return true;
}
}
if (implicitConvergenceAggregatorName != null) {
@SuppressWarnings("unchecked")
Aggregator<Value> aggregator = (Aggregator<Value>) aggregators.get(implicitConvergenceAggregatorName);
if (aggregator == null) {
throw new RuntimeException("Error: Aggregator for default convergence criterion was null.");
}
Value aggregate = aggregator.getAggregate();
if (implicitConvergenceCriterion.isConverged(currentIteration, aggregate)) {
if (log.isInfoEnabled()) {
log.info(formatLogString("empty workset convergence reached after [" + currentIteration
+ "] iterations, terminating..."));
}
return true;
}
}
return false;
}
private void readHeadEventChannel(IntValue rec) throws IOException {
// reset the handler
eventHandler.resetEndOfSuperstep();
// read (and thereby process all events in the handler's event handling functions)
try {
if (this.headEventReader.next(rec)) {
throw new RuntimeException("Synchronization task must not see any records!");
}
} catch (InterruptedException iex) {
// sanity check
if (!(eventHandler.isEndOfSuperstep())) {
throw new RuntimeException("Event handler interrupted without reaching end-of-superstep.");
}
}
}
private void sendToAllWorkers(TaskEvent event) throws IOException, InterruptedException {
headEventReader.sendTaskEvent(event);
}
private String formatLogString(String message) {
return BatchTask.constructLogString(message, getEnvironment().getTaskInfo().getTaskName(), this);
}
// --------------------------------------------------------------------------------------------
@Override
public boolean terminationRequested() {
return terminated.get();
}
@Override
public void requestTermination() {
terminated.set(true);
}
}