org.apache.flink.runtime.state.heap.CopyOnWriteStateMapSnapshot Maven / Gradle / Ivy
/*
* 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.state.heap;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.core.memory.DataOutputView;
import org.apache.flink.runtime.state.StateEntry;
import org.apache.flink.runtime.state.StateSnapshotTransformer;
import org.apache.flink.util.Preconditions;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Objects;
/**
* This class represents the snapshot of a {@link CopyOnWriteStateMap}.
*
* IMPORTANT: Please notice that snapshot integrity of entries in this class rely on proper
* copy-on-write semantics through the {@link CopyOnWriteStateMap} that created the snapshot object,
* but all objects in this snapshot must be considered as READ-ONLY!. The reason is that the objects
* held by this class may or may not be deep copies of original objects that may still used in the
* {@link CopyOnWriteStateMap}. This depends for each entry on whether or not it was subject to
* copy-on-write operations by the {@link CopyOnWriteStateMap}. Phrased differently: the {@link
* CopyOnWriteStateMap} provides copy-on-write isolation for this snapshot, but this snapshot does
* not isolate modifications from the {@link CopyOnWriteStateMap}!
*
* @param type of key
* @param type of namespace
* @param type of state
*/
public class CopyOnWriteStateMapSnapshot
extends StateMapSnapshot> {
/**
* Version of the {@link CopyOnWriteStateMap} when this snapshot was created. This can be used
* to release the snapshot.
*/
private final int snapshotVersion;
/**
* The state map entries, as by the time this snapshot was created. Objects in this array may or
* may not be deep copies of the current entries in the {@link CopyOnWriteStateMap} that created
* this snapshot. This depends for each entry on whether or not it was subject to copy-on-write
* operations by the {@link CopyOnWriteStateMap}.
*/
@Nonnull private final CopyOnWriteStateMap.StateMapEntry[] snapshotData;
/** The number of (non-null) entries in snapshotData. */
@Nonnegative private final int numberOfEntriesInSnapshotData;
/** Whether this snapshot has been released. */
private boolean released;
/**
* Creates a new {@link CopyOnWriteStateMapSnapshot}.
*
* @param owningStateMap the {@link CopyOnWriteStateMap} for which this object represents a
* snapshot.
*/
CopyOnWriteStateMapSnapshot(CopyOnWriteStateMap owningStateMap) {
super(owningStateMap);
this.snapshotData = owningStateMap.snapshotMapArrays();
this.snapshotVersion = owningStateMap.getStateMapVersion();
this.numberOfEntriesInSnapshotData = owningStateMap.size();
this.released = false;
}
@Override
public void release() {
if (!released) {
owningStateMap.releaseSnapshot(this);
released = true;
}
}
public boolean isReleased() {
return released;
}
/**
* Returns the internal version of the {@link CopyOnWriteStateMap} when this snapshot was
* created. This value must be used to tell the {@link CopyOnWriteStateMap} when to release this
* snapshot.
*/
int getSnapshotVersion() {
return snapshotVersion;
}
@Override
public SnapshotIterator getIterator(
@Nonnull TypeSerializer keySerializer,
@Nonnull TypeSerializer namespaceSerializer,
@Nonnull TypeSerializer stateSerializer,
@Nullable final StateSnapshotTransformer stateSnapshotTransformer) {
return stateSnapshotTransformer == null
? new NonTransformSnapshotIterator<>(numberOfEntriesInSnapshotData, snapshotData)
: new TransformedSnapshotIterator<>(
numberOfEntriesInSnapshotData, snapshotData, stateSnapshotTransformer);
}
@Override
public void writeState(
TypeSerializer keySerializer,
TypeSerializer namespaceSerializer,
TypeSerializer stateSerializer,
@Nonnull DataOutputView dov,
@Nullable StateSnapshotTransformer stateSnapshotTransformer)
throws IOException {
SnapshotIterator snapshotIterator =
getIterator(
keySerializer,
namespaceSerializer,
stateSerializer,
stateSnapshotTransformer);
int size = snapshotIterator.size();
dov.writeInt(size);
while (snapshotIterator.hasNext()) {
StateEntry stateEntry = snapshotIterator.next();
namespaceSerializer.serialize(stateEntry.getNamespace(), dov);
keySerializer.serialize(stateEntry.getKey(), dov);
stateSerializer.serialize(stateEntry.getState(), dov);
}
}
/** Iterator over state entries in a {@link CopyOnWriteStateMapSnapshot}. */
abstract static class SnapshotIterator implements Iterator> {
int numberOfEntriesInSnapshotData;
CopyOnWriteStateMap.StateMapEntry[] snapshotData;
Iterator> chainIterator;
Iterator> entryIterator;
SnapshotIterator(
int numberOfEntriesInSnapshotData,
CopyOnWriteStateMap.StateMapEntry[] snapshotData,
@Nullable StateSnapshotTransformer stateSnapshotTransformer) {
this.numberOfEntriesInSnapshotData = numberOfEntriesInSnapshotData;
this.snapshotData = snapshotData;
transform(stateSnapshotTransformer);
this.chainIterator = getChainIterator();
this.entryIterator = Collections.emptyIterator();
}
/** Return the number of state entries in this snapshot. */
abstract int size();
/** Transform the state in the snapshot before iterating the state. */
abstract void transform(@Nullable StateSnapshotTransformer stateSnapshotTransformer);
/** Return an iterator over the chains of entries in snapshotData. */
abstract Iterator> getChainIterator();
/**
* Return an iterator over the entries in the chain.
*
* @param stateMapEntry The head entry of the chain.
*/
abstract Iterator> getEntryIterator(
CopyOnWriteStateMap.StateMapEntry stateMapEntry);
@Override
public boolean hasNext() {
return entryIterator.hasNext() || chainIterator.hasNext();
}
@Override
public CopyOnWriteStateMap.StateMapEntry next() {
if (entryIterator.hasNext()) {
return entryIterator.next();
}
CopyOnWriteStateMap.StateMapEntry stateMapEntry = chainIterator.next();
entryIterator = getEntryIterator(stateMapEntry);
return entryIterator.next();
}
}
/** Implementation of {@link SnapshotIterator} with no transform. */
static class NonTransformSnapshotIterator extends SnapshotIterator {
NonTransformSnapshotIterator(
int numberOfEntriesInSnapshotData,
CopyOnWriteStateMap.StateMapEntry[] snapshotData) {
super(numberOfEntriesInSnapshotData, snapshotData, null);
}
@Override
void transform(@Nullable StateSnapshotTransformer stateSnapshotTransformer) {}
@Override
public int size() {
return numberOfEntriesInSnapshotData;
}
@Override
Iterator> getChainIterator() {
return Arrays.stream(snapshotData).filter(Objects::nonNull).iterator();
}
@Override
Iterator> getEntryIterator(
final CopyOnWriteStateMap.StateMapEntry stateMapEntry) {
return new Iterator>() {
CopyOnWriteStateMap.StateMapEntry nextEntry = stateMapEntry;
@Override
public boolean hasNext() {
return nextEntry != null;
}
@Override
public CopyOnWriteStateMap.StateMapEntry next() {
if (nextEntry == null) {
throw new NoSuchElementException();
}
CopyOnWriteStateMap.StateMapEntry entry = nextEntry;
nextEntry = nextEntry.next;
return entry;
}
};
}
}
/** Implementation of {@link SnapshotIterator} with a {@link StateSnapshotTransformer}. */
static class TransformedSnapshotIterator extends SnapshotIterator {
TransformedSnapshotIterator(
int numberOfEntriesInSnapshotData,
CopyOnWriteStateMap.StateMapEntry[] snapshotData,
@Nonnull StateSnapshotTransformer stateSnapshotTransformer) {
super(numberOfEntriesInSnapshotData, snapshotData, stateSnapshotTransformer);
}
/**
* Move the chains in snapshotData to the back of the array, and return the index of the
* first chain from the front.
*/
int moveChainsToBackOfArray() {
int index = snapshotData.length - 1;
// find the first null chain from the back
while (index >= 0) {
if (snapshotData[index] == null) {
break;
}
index--;
}
int lastNullIndex = index;
index--;
// move the chains to the back
while (index >= 0) {
CopyOnWriteStateMap.StateMapEntry entry = snapshotData[index];
if (entry != null) {
snapshotData[lastNullIndex] = entry;
snapshotData[index] = null;
lastNullIndex--;
}
index--;
}
// return the index of the first chain from the front
return lastNullIndex + 1;
}
@Override
void transform(@Nullable StateSnapshotTransformer stateSnapshotTransformer) {
Preconditions.checkNotNull(stateSnapshotTransformer);
int indexOfFirstChain = moveChainsToBackOfArray();
int count = 0;
// reuse the snapshotData to transform and flatten the entries.
for (int i = indexOfFirstChain; i < snapshotData.length; i++) {
CopyOnWriteStateMap.StateMapEntry entry = snapshotData[i];
while (entry != null) {
S transformedValue = stateSnapshotTransformer.filterOrTransform(entry.state);
if (transformedValue != null) {
CopyOnWriteStateMap.StateMapEntry filteredEntry = entry;
if (transformedValue != entry.state) {
filteredEntry =
new CopyOnWriteStateMap.StateMapEntry<>(
entry, entry.entryVersion);
filteredEntry.state = transformedValue;
}
snapshotData[count++] = filteredEntry;
}
entry = entry.next;
}
}
numberOfEntriesInSnapshotData = count;
}
@Override
public int size() {
return numberOfEntriesInSnapshotData;
}
@Override
Iterator> getChainIterator() {
return Arrays.stream(snapshotData, 0, numberOfEntriesInSnapshotData).iterator();
}
@Override
Iterator> getEntryIterator(
CopyOnWriteStateMap.StateMapEntry stateMapEntry) {
return Collections.singleton(stateMapEntry).iterator();
}
}
}