gemini-code-assist[bot] commented on code in PR #38767: URL: https://github.com/apache/beam/pull/38767#discussion_r3340029109
########## runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/util/KeyGroupWorkQueue.java: ########## @@ -0,0 +1,463 @@ +/* + * 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.beam.runners.dataflow.worker.util; + +import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull; + +import java.util.AbstractQueue; +import java.util.ArrayList; +import java.util.Collection; +import java.util.Collections; +import java.util.HashMap; +import java.util.Iterator; +import java.util.List; +import java.util.Map; +import java.util.Objects; +import java.util.concurrent.BlockingQueue; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.locks.Condition; +import java.util.concurrent.locks.ReentrantLock; +import org.apache.beam.runners.dataflow.worker.streaming.Work; +import org.apache.beam.runners.dataflow.worker.util.BoundedQueueExecutor.QueuedWork; +import org.checkerframework.checker.nullness.qual.Nullable; + +/** + * A custom, thread-safe doubly-linked BlockingQueue. In addition to global FIFO ordering, the queue + * supports polling work by computation + key group in FIFO order + */ +class KeyGroupWorkQueue extends AbstractQueue<Runnable> implements BlockingQueue<Runnable> { + + static class Node { + final @Nullable Runnable task; + final @Nullable String computationId; + final Work.@Nullable KeyGroup keyGroup; + + // prevNode, nextNode are used for the global order across all queued Runnables + @Nullable Node prevNode; + @Nullable Node nextNode; + + // prevKeyGroupNode and nextKeyGroupNode are used for the keyGroup level lists linking + // QueuedWork with same keyGroup + @Nullable Node prevKeyGroupNode; + @Nullable Node nextKeyGroupNode; + + Node(@Nullable Runnable task) { + this.task = task; + if (task instanceof QueuedWork) { + this.computationId = ((QueuedWork) task).getWork().getComputationId(); + this.keyGroup = ((QueuedWork) task).getWork().getKeyGroup().orElse(null); + } else { + this.computationId = null; + this.keyGroup = null; + } + } + } + + /** Double linked list implementing key group level queue */ + private static class KeyGroupWorkList { + final Node head; + final Node tail; + + KeyGroupWorkList() { + head = new Node(null); + tail = new Node(null); + head.nextKeyGroupNode = tail; + tail.prevKeyGroupNode = head; + } + + boolean isEmpty() { + return head.nextKeyGroupNode == tail; + } + + void append(Node node) { + @Nullable Node last = tail.prevKeyGroupNode; + if (last == null) { + throw new NullPointerException("tail.prevComp is null"); + } + node.prevKeyGroupNode = last; + node.nextKeyGroupNode = tail; + last.nextKeyGroupNode = node; + tail.prevKeyGroupNode = node; + } + + void remove(Node node) { + @Nullable Node prev = node.prevKeyGroupNode; + @Nullable Node next = node.nextKeyGroupNode; + if (prev != null && next != null) { + prev.nextKeyGroupNode = next; + next.prevKeyGroupNode = prev; + node.prevKeyGroupNode = null; + node.nextKeyGroupNode = null; + } + } + } + + private final ReentrantLock lock = new ReentrantLock(); + private final Condition notEmpty = lock.newCondition(); + + // Sentinels for the global list + private final Node globalHead = new Node(null); + private final Node globalTail = new Node(null); + + private final Map<QueueKey, KeyGroupWorkList> keyGroupQueueMap = new HashMap<>(); + + private int size = 0; + + public KeyGroupWorkQueue() { + globalHead.nextNode = globalTail; + globalTail.prevNode = globalHead; + } + + private void unlinkNode(Node node) { + // 1. Unlink from global list + Node prevG = node.prevNode; + Node nextG = node.nextNode; + if (prevG != null && nextG != null) { + prevG.nextNode = nextG; + nextG.prevNode = prevG; + } + node.prevNode = null; + node.nextNode = null; Review Comment:  To prevent potential issues with double-unlinking (e.g., if `unlinkNode` is called multiple times on the same node due to future refactoring or concurrent edge cases), we should add a defensive check at the beginning of the method. If both `prevNode` and `nextNode` are null, the node is already unlinked, and we can return early to avoid corrupting the queue's `size` and internal state. ```java private void unlinkNode(Node node) { if (node.prevNode == null && node.nextNode == null) { return; } // 1. Unlink from global list Node prevG = node.prevNode; Node nextG = node.nextNode; if (prevG != null && nextG != null) { prevG.nextNode = nextG; nextG.prevNode = prevG; } node.prevNode = null; node.nextNode = null; ``` ########## runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/util/KeyGroupWorkQueue.java: ########## @@ -0,0 +1,463 @@ +/* + * 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.beam.runners.dataflow.worker.util; + +import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull; + +import java.util.AbstractQueue; +import java.util.ArrayList; +import java.util.Collection; +import java.util.Collections; +import java.util.HashMap; +import java.util.Iterator; +import java.util.List; +import java.util.Map; +import java.util.Objects; +import java.util.concurrent.BlockingQueue; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.locks.Condition; +import java.util.concurrent.locks.ReentrantLock; +import org.apache.beam.runners.dataflow.worker.streaming.Work; +import org.apache.beam.runners.dataflow.worker.util.BoundedQueueExecutor.QueuedWork; +import org.checkerframework.checker.nullness.qual.Nullable; + +/** + * A custom, thread-safe doubly-linked BlockingQueue. In addition to global FIFO ordering, the queue + * supports polling work by computation + key group in FIFO order + */ +class KeyGroupWorkQueue extends AbstractQueue<Runnable> implements BlockingQueue<Runnable> { + + static class Node { + final @Nullable Runnable task; + final @Nullable String computationId; + final Work.@Nullable KeyGroup keyGroup; + + // prevNode, nextNode are used for the global order across all queued Runnables + @Nullable Node prevNode; + @Nullable Node nextNode; + + // prevKeyGroupNode and nextKeyGroupNode are used for the keyGroup level lists linking + // QueuedWork with same keyGroup + @Nullable Node prevKeyGroupNode; + @Nullable Node nextKeyGroupNode; + + Node(@Nullable Runnable task) { + this.task = task; + if (task instanceof QueuedWork) { + this.computationId = ((QueuedWork) task).getWork().getComputationId(); + this.keyGroup = ((QueuedWork) task).getWork().getKeyGroup().orElse(null); + } else { + this.computationId = null; + this.keyGroup = null; + } + } + } + + /** Double linked list implementing key group level queue */ + private static class KeyGroupWorkList { + final Node head; + final Node tail; + + KeyGroupWorkList() { + head = new Node(null); + tail = new Node(null); + head.nextKeyGroupNode = tail; + tail.prevKeyGroupNode = head; + } + + boolean isEmpty() { + return head.nextKeyGroupNode == tail; + } + + void append(Node node) { + @Nullable Node last = tail.prevKeyGroupNode; + if (last == null) { + throw new NullPointerException("tail.prevComp is null"); + } + node.prevKeyGroupNode = last; + node.nextKeyGroupNode = tail; + last.nextKeyGroupNode = node; + tail.prevKeyGroupNode = node; + } + + void remove(Node node) { + @Nullable Node prev = node.prevKeyGroupNode; + @Nullable Node next = node.nextKeyGroupNode; + if (prev != null && next != null) { + prev.nextKeyGroupNode = next; + next.prevKeyGroupNode = prev; + node.prevKeyGroupNode = null; + node.nextKeyGroupNode = null; + } + } + } + + private final ReentrantLock lock = new ReentrantLock(); + private final Condition notEmpty = lock.newCondition(); + + // Sentinels for the global list + private final Node globalHead = new Node(null); + private final Node globalTail = new Node(null); + + private final Map<QueueKey, KeyGroupWorkList> keyGroupQueueMap = new HashMap<>(); + + private int size = 0; + + public KeyGroupWorkQueue() { + globalHead.nextNode = globalTail; + globalTail.prevNode = globalHead; + } + + private void unlinkNode(Node node) { + // 1. Unlink from global list + Node prevG = node.prevNode; + Node nextG = node.nextNode; + if (prevG != null && nextG != null) { + prevG.nextNode = nextG; + nextG.prevNode = prevG; + } + node.prevNode = null; + node.nextNode = null; + + // 2. Unlink from key group list + if (node.computationId != null) { + QueueKey key = QueueKey.create(node.computationId, node.keyGroup); + KeyGroupWorkList keyGroupQueue = keyGroupQueueMap.get(key); + if (keyGroupQueue != null) { + keyGroupQueue.remove(node); + if (keyGroupQueue.isEmpty()) { + keyGroupQueueMap.remove(key); + } + } + } + --size; + } + + private @Nullable Node removeFirstGlobal() { + @Nullable Node first = globalHead.nextNode; + if (first == null || first == globalTail) { + return null; + } + unlinkNode(first); + return first; + } + + /** + * Remove and Return QueuedWork for the computationId, keyGroup in the FIFO order Returns null, if + * there are no matches. + */ + public @Nullable QueuedWork pollWork(String computationId, Work.KeyGroup keyGroup) { + if (computationId == null || keyGroup == null) { + return null; + } + lock.lock(); + try { + QueueKey key = QueueKey.create(computationId, keyGroup); + KeyGroupWorkList keyGroupWorkList = keyGroupQueueMap.get(key); + if (keyGroupWorkList == null || keyGroupWorkList.isEmpty()) { + return null; + } + + // Retrieve the first pending task for this computation and keyGroup in O(1) + @Nullable Node firstNode = keyGroupWorkList.head.nextKeyGroupNode; + if (firstNode == null || firstNode == keyGroupWorkList.tail) { + return null; + } + unlinkNode(firstNode); + + Runnable task = firstNode.task; + if (task == null) { + return null; + } + return (QueuedWork) task; + } finally { + lock.unlock(); + } + } + + @Override + public boolean offer(Runnable runnable) { + if (runnable == null) throw new NullPointerException(); + lock.lock(); + try { + Node node = new Node(runnable); + + // Append to global list tail + @Nullable Node lastG = globalTail.prevNode; + if (lastG == null) { + throw new NullPointerException("globalTail.prevNode is null"); + } + node.prevNode = lastG; + node.nextNode = globalTail; + lastG.nextNode = node; + globalTail.prevNode = node; + + // Append to key group list if applicable + if (node.computationId != null) { + QueueKey key = QueueKey.create(node.computationId, node.keyGroup); + KeyGroupWorkList keyGroupWorkList = + keyGroupQueueMap.computeIfAbsent(key, k -> new KeyGroupWorkList()); + keyGroupWorkList.append(node); + } + + ++size; + notEmpty.signal(); + return true; + } finally { + lock.unlock(); + } + } + + @Override + public void put(Runnable e) throws InterruptedException { + offer(e); // Unbounded queue + } + + @Override + public boolean offer(Runnable e, long timeout, TimeUnit unit) throws InterruptedException { + return offer(e); // Unbounded queue + } + + @Override + public @Nullable Runnable poll() { + lock.lock(); + try { + @Nullable Node node = removeFirstGlobal(); + return (node != null) ? node.task : null; + } finally { + lock.unlock(); + } + } + + @Override + public Runnable take() throws InterruptedException { + lock.lockInterruptibly(); + try { + while (size == 0) { + notEmpty.await(); + } + @Nullable Node node = removeFirstGlobal(); + checkStateNotNull(node, "Queue is empty but size was " + size); + Runnable task = node.task; + checkStateNotNull(task, "Encountered null task in queue"); + return task; Review Comment:  In environments with strict nullness checking (such as the Checker Framework used in Beam), calling `checkStateNotNull` without reassigning the result to a non-nullable variable can still trigger static analysis warnings when dereferencing the original `@Nullable` reference. Reassigning the non-null result of `checkStateNotNull` to a non-nullable variable is the standard and safe way to satisfy the compiler and static analysis tools. ```suggestion Node node = checkStateNotNull(removeFirstGlobal(), "Queue is empty but size was " + size); Runnable task = checkStateNotNull(node.task, "Encountered null task in queue"); return task; ``` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
