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https://issues.apache.org/jira/browse/FLINK-9423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16493606#comment-16493606
]
ASF GitHub Bot commented on FLINK-9423:
---------------------------------------
Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/6062#discussion_r191426419
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/InternalTimerHeap.java
---
@@ -0,0 +1,511 @@
+/*
+ * 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.streaming.api.operators;
+
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.runtime.state.KeyGroupRange;
+import org.apache.flink.runtime.state.KeyGroupRangeAssignment;
+
+import javax.annotation.Nonnegative;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.Queue;
+import java.util.Set;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+
+/**
+ * A heap-based priority queue for internal timers. This heap is supported
by hash sets for fast contains
+ * (de-duplication) and deletes. The heap implementation is a simple
binary tree stored inside an array. Element indexes
+ * in the heap array start at 1 instead of 0 to make array index
computations a bit simpler in the hot methods.
+ *
+ * <p>Possible future improvements:
+ * <ul>
+ * <li>We could also implement shrinking for the heap and the
deduplication maps.</li>
+ * <li>We could replace the deduplication maps with more efficient custom
implementations. In particular, a hash set
+ * would be enough if it could return existing elements on unsuccessful
adding, etc..</li>
+ * </ul>
+ *
+ * @param <K> type of the key of the internal timers managed by this
priority queue.
+ * @param <N> type of the namespace of the internal timers managed by this
priority queue.
+ */
+public class InternalTimerHeap<K, N> implements
Queue<TimerHeapInternalTimer<K, N>>, Set<TimerHeapInternalTimer<K, N>> {
+
+ /**
+ * A safe maximum size for arrays in the JVM.
+ */
+ private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
+
+ /**
+ * Comparator for {@link TimerHeapInternalTimer}, based on the
timestamp in ascending order.
+ */
+ private static final Comparator<TimerHeapInternalTimer<?, ?>>
COMPARATOR =
+ (o1, o2) -> Long.compare(o1.getTimestamp(), o2.getTimestamp());
+
+ /**
+ * This array contains one hash set per key-group. The sets are used
for fast de-duplication and deletes of timers.
+ */
+ private final HashMap<TimerHeapInternalTimer<K, N>,
TimerHeapInternalTimer<K, N>>[] deduplicationMapsByKeyGroup;
+
+ /**
+ * The array that represents the heap-organized priority queue.
+ */
+ private TimerHeapInternalTimer<K, N>[] queue;
+
+ /**
+ * The current size of the priority queue.
+ */
+ private int size;
+
+ /**
+ * The key-group range of timers that are managed by this queue.
+ */
+ private final KeyGroupRange keyGroupRange;
+
+ /**
+ * The total number of key-groups of the job.
+ */
+ private final int totalNumberOfKeyGroups;
+
+
+ /**
+ * Creates an empty {@link InternalTimerHeap} with the requested
initial capacity.
+ *
+ * @param minimumCapacity the minimum and initial capacity of this
priority queue.
+ */
+ @SuppressWarnings("unchecked")
+ InternalTimerHeap(
+ @Nonnegative int minimumCapacity,
+ @Nonnull KeyGroupRange keyGroupRange,
+ @Nonnegative int totalNumberOfKeyGroups) {
+
+ this.totalNumberOfKeyGroups = totalNumberOfKeyGroups;
+ this.keyGroupRange = keyGroupRange;
+
+ final int keyGroupsInLocalRange =
keyGroupRange.getNumberOfKeyGroups();
+ final int deduplicationSetSize = 1 + minimumCapacity /
keyGroupsInLocalRange;
+ this.deduplicationMapsByKeyGroup = new
HashMap[keyGroupsInLocalRange];
+ for (int i = 0; i < keyGroupsInLocalRange; ++i) {
+ deduplicationMapsByKeyGroup[i] = new
HashMap<>(deduplicationSetSize);
+ }
+
+ this.queue = new TimerHeapInternalTimer[1 + minimumCapacity];
+ }
+
+ /**
+ * @see Set#add(Object)
+ */
+ @Override
+ public boolean add(@Nonnull TimerHeapInternalTimer<K, N> timer) {
+
+ if (getDedupMapForKeyGroup(timer).putIfAbsent(timer, timer) ==
null) {
+ final int newSize = ++this.size;
+ growIfRequired(newSize);
+ moveElementToIdx(timer, newSize);
+ siftUp(newSize);
+ return true;
+ } else {
+ return false;
+ }
+ }
+
+ /**
+ * This behaves like {@link #add(TimerHeapInternalTimer)}.
+ */
+ @Override
+ public boolean offer(@Nonnull TimerHeapInternalTimer<K, N> k) {
+ return add(k);
+ }
+
+ @Nullable
+ @Override
+ public TimerHeapInternalTimer<K, N> poll() {
+ return size() > 0 ? removeElementAtIndex(1) : null;
+ }
+
+ @Nonnull
+ @Override
+ public TimerHeapInternalTimer<K, N> remove() {
+ TimerHeapInternalTimer<K, N> pollResult = poll();
+ if (pollResult != null) {
+ return pollResult;
+ } else {
+ throw new
NoSuchElementException("InternalTimerPriorityQueue is empty.");
+ }
+ }
+
+ @Nullable
+ @Override
+ public TimerHeapInternalTimer<K, N> peek() {
+ return size() > 0 ? queue[1] : null;
+ }
+
+ @Nonnull
+ @Override
+ public TimerHeapInternalTimer<K, N> element() {
+ TimerHeapInternalTimer<K, N> peekResult = peek();
+ if (peekResult != null) {
+ return peekResult;
+ } else {
+ throw new
NoSuchElementException("InternalTimerPriorityQueue is empty.");
+ }
+ }
+
+ @Override
+ public boolean isEmpty() {
+ return size() == 0;
+ }
+
+ @Override
+ public boolean contains(@Nullable Object toCheck) {
+ return (toCheck instanceof TimerHeapInternalTimer)
+ && getDedupMapForKeyGroup((TimerHeapInternalTimer<?,
?>) toCheck).containsKey(toCheck);
+ }
+
+ @Override
+ public boolean remove(@Nullable Object toRemove) {
+ if (toRemove instanceof TimerHeapInternalTimer) {
+ return removeInternal((TimerHeapInternalTimer<?, ?>)
toRemove);
+ }
+ return false;
+ }
+
+ @Override
+ public boolean addAll(@Nullable Collection<? extends
TimerHeapInternalTimer<K, N>> timers) {
+
+ if (timers == null) {
+ return true;
+ }
+
+ final int oldSize = size();
+ resizeForBulkLoad(oldSize + timers.size());
+
+ for (TimerHeapInternalTimer<K, N> k : timers) {
+ add(k);
+ }
+
+ return oldSize != size();
+ }
+
+ @Nonnull
+ @Override
+ public Object[] toArray() {
+ return Arrays.copyOfRange(queue, 1, size + 1);
+ }
+
+ @SuppressWarnings({"unchecked", "SuspiciousSystemArraycopy"})
+ @Nonnull
+ @Override
+ public <T> T[] toArray(@Nonnull T[] array) {
+ if (array.length >= size) {
+ System.arraycopy(queue, 1, array, 0, size);
+ return array;
+ }
+ return (T[]) Arrays.copyOfRange(queue, 1, size + 1,
array.getClass());
+ }
+
+ @Override
+ public boolean removeAll(@Nullable Collection<?> toRemove) {
+
+ if (toRemove == null) {
+ return false;
+ }
+
+ int oldSize = size();
+ for (Object o : toRemove) {
+ remove(o);
+ }
+ return oldSize != size();
+ }
+
+ /**
+ * Returns an iterator over the elements in this queue. The iterator
+ * does not return the elements in any particular order.
+ *
+ * @return an iterator over the elements in this queue.
+ */
+ @Nonnull
+ @Override
+ public Iterator<TimerHeapInternalTimer<K, N>> iterator() {
+ return new InternalTimerPriorityQueueIterator();
+ }
+
+ @Override
+ public boolean containsAll(@Nullable Collection<?> toCheck) {
+
+ if (toCheck == null) {
+ return true;
+ }
+
+ for (Object o : toCheck) {
+ if (!contains(o)) {
+ return false;
+ }
+ }
+
+ return true;
+ }
+
+ @Nonnegative
+ @Override
+ public int size() {
+ return size;
+ }
+
+ @Override
+ public void clear() {
+
+ Arrays.fill(queue, null);
+ for (HashMap<TimerHeapInternalTimer<K, N>,
TimerHeapInternalTimer<K, N>> timerHashMap :
+ deduplicationMapsByKeyGroup) {
+ timerHashMap.clear();
+ }
+ size = 0;
+ }
+
+ /**
+ * This method is currently not implemented.
+ */
+ @Override
+ public boolean retainAll(@Nullable Collection<?> toRetain) {
+ throw new UnsupportedOperationException();
+ }
+
+ /**
+ * Adds a new timer with the given timestamp, key, and namespace to the
heap, if an identical timer was not yet
+ * registered.
+ *
+ * @param timestamp the timer timestamp.
+ * @param key the timer key.
+ * @param namespace the timer namespace.
+ * @return true iff a new timer with given timestamp, key, and
namespace was added to the heap.
+ */
+ boolean scheduleTimer(long timestamp, K key, N namespace) {
+ return add(new TimerHeapInternalTimer<>(timestamp, key,
namespace));
+ }
+
+ /**
+ * Stops timer with the given timestamp, key, and namespace by removing
it from the heap, if it exists on the heap.
+ *
+ * @param timestamp the timer timestamp.
+ * @param key the timer key.
+ * @param namespace the timer namespace.
+ * @return true iff a timer with given timestamp, key, and namespace
was found and removed from the heap.
+ */
+ boolean stopTimer(long timestamp, K key, N namespace) {
+ return removeInternal(new TimerHeapInternalTimer<>(timestamp,
key, namespace));
+ }
+
+ /**
+ * This method adds all the given timers to the heap.
+ */
+ void addRestoredTimers(Collection<? extends InternalTimer<K, N>>
restoredTimers) {
+
+ if (restoredTimers == null) {
+ return;
+ }
+
+ resizeForBulkLoad(restoredTimers.size());
+
+ for (InternalTimer<K, N> timer : restoredTimers) {
+ if (timer instanceof TimerHeapInternalTimer) {
+ add((TimerHeapInternalTimer<K, N>) timer);
+ } else {
+ scheduleTimer(timer.getTimestamp(),
timer.getKey(), timer.getNamespace());
+ }
+ }
+ }
+
+ private boolean removeInternal(TimerHeapInternalTimer<?, ?>
timerToRemove) {
+
+ TimerHeapInternalTimer<K, N> storedTimer =
getDedupMapForKeyGroup(timerToRemove).remove(timerToRemove);
+
+ if (storedTimer != null) {
+ removeElementAtIndex(storedTimer.getTimerHeapIndex());
+ return true;
+ }
+
+ return false;
+ }
+
+ private TimerHeapInternalTimer<K, N> removeElementAtIndex(int
removeIdx) {
+ TimerHeapInternalTimer<K, N>[] heap = this.queue;
+ TimerHeapInternalTimer<K, N> removedValue = heap[removeIdx];
+
+ assert removedValue.getTimerHeapIndex() == removeIdx;
+
+ final int oldSize = size;
+
+ if (removeIdx != oldSize) {
+ TimerHeapInternalTimer<K, N> timer = heap[oldSize];
+ moveElementToIdx(timer, removeIdx);
+ siftDown(removeIdx);
+ if (heap[removeIdx] == timer) {
+ siftUp(removeIdx);
+ }
+ }
+
+ heap[oldSize] = null;
+ getDedupMapForKeyGroup(removedValue).remove(removedValue);
+
+ --size;
+ return removedValue;
+ }
+
+ private void siftUp(int idx) {
+ final TimerHeapInternalTimer<K, N>[] heap = this.queue;
+ TimerHeapInternalTimer<K, N> currentTimer = heap[idx];
+ int parentIdx = idx >>> 1;
+
+ while (parentIdx > 0 && COMPARATOR.compare(currentTimer,
heap[parentIdx]) < 0) {
+ moveElementToIdx(heap[parentIdx], idx);
+ idx = parentIdx;
+ parentIdx = parentIdx >>> 1;
+ }
+
+ moveElementToIdx(currentTimer, idx);
+ }
+
+ private void siftDown(int idx) {
+ final TimerHeapInternalTimer<K, N>[] heap = this.queue;
+ final int heapSize = this.size;
+
+ TimerHeapInternalTimer<K, N> currentTimer = heap[idx];
+ int firstChildIdx = idx << 1;
+ int secondChildIdx = firstChildIdx + 1;
+
+ if (secondChildIdx <= heapSize &&
COMPARATOR.compare(heap[secondChildIdx], heap[firstChildIdx]) < 0) {
+ firstChildIdx = secondChildIdx;
+ }
+
+ while (firstChildIdx <= heapSize &&
COMPARATOR.compare(heap[firstChildIdx], currentTimer) < 0) {
+ moveElementToIdx(heap[firstChildIdx], idx);
+ idx = firstChildIdx;
+ firstChildIdx = idx << 1;
+ secondChildIdx = firstChildIdx + 1;
+
+ if (secondChildIdx <= heapSize &&
COMPARATOR.compare(heap[secondChildIdx], heap[firstChildIdx]) < 0) {
+ firstChildIdx = secondChildIdx;
+ }
--- End diff --
This looks like a code duplication. I think this could be refactored into a
private method.
> Implement efficient deletes for heap based timer service
> --------------------------------------------------------
>
> Key: FLINK-9423
> URL: https://issues.apache.org/jira/browse/FLINK-9423
> Project: Flink
> Issue Type: Improvement
> Components: Streaming
> Affects Versions: 1.5.0
> Reporter: Stefan Richter
> Assignee: Stefan Richter
> Priority: Major
> Fix For: 1.6.0
>
>
> The current data structures in the `HeapInternalTimerService` are not able to
> support efficient timer deletes, the complexity is currently O\(n\), where n
> is the number of registered timers.
>
> We can keep track of timer's positions in the priority queue and (in
> combination with the already existing set/map) have a more efficient
> algorithm for deletes.
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