/*
* 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.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.flink.api.common.functions.Function;
import org.apache.flink.runtime.iterative.concurrent.SolutionSetUpdateBarrier;
import org.apache.flink.runtime.iterative.concurrent.SolutionSetUpdateBarrierBroker;
import org.apache.flink.runtime.iterative.concurrent.SuperstepKickoffLatch;
import org.apache.flink.runtime.iterative.concurrent.SuperstepKickoffLatchBroker;
import org.apache.flink.runtime.iterative.io.WorksetUpdateOutputCollector;
import org.apache.flink.util.Collector;
/**
* An iteration tail, which runs a driver inside.
* <p/>
* If the iteration state is updated, the output of this task will be send back to the {@link IterationHeadPactTask} via
* a BackChannel for the workset -OR- a HashTable for the solution set. Therefore this
* task must be scheduled on the same instance as the head. It's also possible for the tail to update *both* the workset
* and the solution set.
* <p/>
* If there is a separate solution set tail, the iteration head has to make sure to wait for it to finish.
*/
public class IterationTailPactTask<S extends Function, OT> extends AbstractIterativePactTask<S, OT> {
private static final Logger log = LoggerFactory.getLogger(IterationTailPactTask.class);
private SolutionSetUpdateBarrier solutionSetUpdateBarrier;
private WorksetUpdateOutputCollector<OT> worksetUpdateOutputCollector;
@Override
protected void initialize() throws Exception {
super.initialize();
// sanity check: the tail has to update either the workset or the solution set
if (!isWorksetUpdate && !isSolutionSetUpdate) {
throw new RuntimeException("The iteration tail doesn't update workset or the solution set.");
}
// set the last output collector of this task to reflect the iteration tail state update:
// a) workset update,
// b) solution set update, or
// c) merged workset and solution set update
Collector<OT> outputCollector = null;
if (isWorksetUpdate) {
outputCollector = createWorksetUpdateOutputCollector();
// we need the WorksetUpdateOutputCollector separately to count the collected elements
if (isWorksetIteration) {
worksetUpdateOutputCollector = (WorksetUpdateOutputCollector<OT>) outputCollector;
}
}
if (isSolutionSetUpdate) {
if (isWorksetIteration) {
outputCollector = createSolutionSetUpdateOutputCollector(outputCollector);
}
// Bulk iteration with termination criterion
else {
outputCollector = new Collector<OT>() {
@Override
public void collect(OT record) {}
@Override
public void close() {}
};
}
if (!isWorksetUpdate) {
solutionSetUpdateBarrier = SolutionSetUpdateBarrierBroker.instance().get(brokerKey());
}
}
setLastOutputCollector(outputCollector);
}
@Override
public void run() throws Exception {
SuperstepKickoffLatch nextSuperStepLatch = SuperstepKickoffLatchBroker.instance().get(brokerKey());
while (this.running && !terminationRequested()) {
if (log.isInfoEnabled()) {
log.info(formatLogString("starting iteration [" + currentIteration() + "]"));
}
super.run();
// check if termination was requested
verifyEndOfSuperstepState();
if (isWorksetUpdate && isWorksetIteration) {
// aggregate workset update element count
long numCollected = worksetUpdateOutputCollector.getElementsCollectedAndReset();
worksetAggregator.aggregate(numCollected);
}
if (log.isInfoEnabled()) {
log.info(formatLogString("finishing iteration [" + currentIteration() + "]"));
}
if (isWorksetUpdate) {
// notify iteration head if responsible for workset update
worksetBackChannel.notifyOfEndOfSuperstep();
} else if (isSolutionSetUpdate) {
// notify iteration head if responsible for solution set update
solutionSetUpdateBarrier.notifySolutionSetUpdate();
}
boolean terminate = nextSuperStepLatch.awaitStartOfSuperstepOrTermination(currentIteration() + 1);
if (terminate) {
requestTermination();
}
else {
incrementIterationCounter();
}
}
}
}