org.apache.flink.runtime.broadcast.BroadcastVariableMaterialization Maven / Gradle / Ivy
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* distributed with this work for additional information
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* 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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.runtime.broadcast;
import org.apache.flink.api.common.functions.BroadcastVariableInitializer;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.common.typeutils.TypeSerializerFactory;
import org.apache.flink.runtime.io.network.api.reader.MutableReader;
import org.apache.flink.runtime.operators.BatchTask;
import org.apache.flink.runtime.operators.util.ReaderIterator;
import org.apache.flink.runtime.plugable.DeserializationDelegate;
import org.apache.flink.util.Preconditions;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* This class represents a single materialization of a broadcast variable and maintains a reference count for it. If the
* reference count reaches zero the variable is no longer accessible and will eventually be garbage-collected.
*
* @param The type of the elements in the broadcast data set.
*/
public class BroadcastVariableMaterialization {
private static final Logger LOG = LoggerFactory.getLogger(BroadcastVariableMaterialization.class);
private final Set> references = new HashSet>();
private final Object materializationMonitor = new Object();
private final BroadcastVariableKey key;
private ArrayList data;
private C transformed;
private boolean materialized;
private boolean disposed;
public BroadcastVariableMaterialization(BroadcastVariableKey key) {
this.key = key;
}
// --------------------------------------------------------------------------------------------
public void materializeVariable(MutableReader reader, TypeSerializerFactory serializerFactory, BatchTask referenceHolder)
throws MaterializationExpiredException, IOException {
Preconditions.checkNotNull(reader);
Preconditions.checkNotNull(serializerFactory);
Preconditions.checkNotNull(referenceHolder);
final boolean materializer;
// hold the reference lock only while we track references and decide who should be the materializer
// that way, other tasks can de-register (in case of failure) while materialization is happening
synchronized (references) {
if (disposed) {
throw new MaterializationExpiredException();
}
// sanity check
if (!references.add(referenceHolder)) {
throw new IllegalStateException(
String.format("The task %s already holds a reference to the broadcast variable %s.",
referenceHolder.getEnvironment().getTaskInfo().getTaskNameWithSubtasks(),
key.toString()));
}
materializer = references.size() == 1;
}
try {
@SuppressWarnings("unchecked")
final MutableReader> typedReader = (MutableReader>) reader;
@SuppressWarnings("unchecked")
final TypeSerializer serializer = ((TypeSerializerFactory) serializerFactory).getSerializer();
final ReaderIterator readerIterator = new ReaderIterator(typedReader, serializer);
if (materializer) {
// first one, so we need to materialize;
if (LOG.isDebugEnabled()) {
LOG.debug("Getting Broadcast Variable (" + key + ") - First access, materializing.");
}
ArrayList data = new ArrayList();
T element;
while ((element = readerIterator.next()) != null) {
data.add(element);
}
synchronized (materializationMonitor) {
this.data = data;
this.materialized = true;
materializationMonitor.notifyAll();
}
if (LOG.isDebugEnabled()) {
LOG.debug("Materialization of Broadcast Variable (" + key + ") finished.");
}
}
else {
// successor: discard all data and refer to the shared variable
if (LOG.isDebugEnabled()) {
LOG.debug("Getting Broadcast Variable (" + key + ") - shared access.");
}
T element = serializer.createInstance();
while ((element = readerIterator.next(element)) != null) {
}
synchronized (materializationMonitor) {
while (!this.materialized && !disposed) {
materializationMonitor.wait();
}
}
}
}
catch (Throwable t) {
// in case of an exception, we need to clean up big time
decrementReferenceIfHeld(referenceHolder);
if (t instanceof IOException) {
throw (IOException) t;
} else {
throw new IOException("Materialization of the broadcast variable failed.", t);
}
}
}
public boolean decrementReference(BatchTask referenceHolder) {
return decrementReferenceInternal(referenceHolder, true);
}
public boolean decrementReferenceIfHeld(BatchTask referenceHolder) {
return decrementReferenceInternal(referenceHolder, false);
}
private boolean decrementReferenceInternal(BatchTask referenceHolder, boolean errorIfNoReference) {
synchronized (references) {
if (disposed || references.isEmpty()) {
if (errorIfNoReference) {
throw new IllegalStateException("Decrementing reference to broadcast variable that is no longer alive.");
} else {
return false;
}
}
if (!references.remove(referenceHolder)) {
if (errorIfNoReference) {
throw new IllegalStateException(
String.format("The task %s did not hold a reference to the broadcast variable %s.",
referenceHolder.getEnvironment().getTaskInfo().getTaskNameWithSubtasks(),
key.toString()));
} else {
return false;
}
}
if (references.isEmpty()) {
disposed = true;
data = null;
transformed = null;
return true;
} else {
return false;
}
}
}
// --------------------------------------------------------------------------------------------
public List getVariable() throws InitializationTypeConflictException {
if (!materialized) {
throw new IllegalStateException("The Broadcast Variable has not yet been materialized.");
}
if (disposed) {
throw new IllegalStateException("The Broadcast Variable has been disposed");
}
synchronized (references) {
if (transformed != null) {
if (transformed instanceof List) {
@SuppressWarnings("unchecked")
List casted = (List) transformed;
return casted;
} else {
throw new InitializationTypeConflictException(transformed.getClass());
}
}
else {
return data;
}
}
}
public C getVariable(BroadcastVariableInitializer initializer) {
if (!materialized) {
throw new IllegalStateException("The Broadcast Variable has not yet been materialized.");
}
if (disposed) {
throw new IllegalStateException("The Broadcast Variable has been disposed");
}
synchronized (references) {
if (transformed == null) {
transformed = initializer.initializeBroadcastVariable(data);
data = null;
}
return transformed;
}
}
}