[GitHub] [bookkeeper] horizonzy commented on a diff in pull request #3838: Added BatchedArrayBlockingQueue

["horizonzy (via GitHub)" <gi...@apache.org>]

horizonzy commented on code in PR #3838:
URL: https://github.com/apache/bookkeeper/pull/3838#discussion_r1127285821


##########
bookkeeper-common/src/main/java/org/apache/bookkeeper/common/collections/BatchedArrayBlockingQueue.java:
##########
@@ -0,0 +1,409 @@
+/*
+ *
+ * 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.bookkeeper.common.collections;
+
+import java.util.AbstractQueue;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * This implements a {@link BlockingQueue} backed by an array with fixed capacity.
+ *
+ * <p>This queue only allows 1 consumer thread to dequeue items and multiple producer threads.
+ */
+public class BatchedArrayBlockingQueue<T>
+        extends AbstractQueue<T>
+        implements BlockingQueue<T>, BatchedBlockingQueue<T> {
+
+    private final ReentrantLock lock = new ReentrantLock();
+
+    private final Condition notEmpty = lock.newCondition();
+    private final Condition notFull = lock.newCondition();
+
+    private final int capacity;
+    private final T[] data;
+
+    private int size;
+
+    private int consumerIdx;
+    private int producerIdx;
+
+    @SuppressWarnings("unchecked")
+    public BatchedArrayBlockingQueue(int capacity) {
+        this.capacity = capacity;
+        this.data = (T[]) new Object[this.capacity];
+    }
+
+    private T dequeueOne() {
+        T item = data[consumerIdx];
+        data[consumerIdx] = null;
+        if (++consumerIdx == capacity) {
+            consumerIdx = 0;
+        }
+
+        if (size-- == capacity) {
+            notFull.signalAll();
+        }
+
+        return item;
+    }
+
+    private void enqueueOne(T item) {
+        data[producerIdx] = item;
+        if (++producerIdx == capacity) {
+            producerIdx = 0;
+        }
+
+        if (size++ == 0) {
+            notEmpty.signalAll();
+        }
+    }
+
+    @Override
+    public T poll() {
+        lock.lock();
+
+        try {
+            if (size == 0) {
+                return null;
+            }
+
+            return dequeueOne();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public T peek() {
+        lock.lock();
+
+        try {
+            if (size == 0) {
+                return null;
+            }
+
+            return data[consumerIdx];
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public boolean offer(T e) {
+        lock.lock();
+
+        try {
+            if (size == capacity) {
+                return false;
+            }
+
+            enqueueOne(e);
+
+            return true;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public void put(T e) throws InterruptedException {
+        lock.lockInterruptibly();
+
+        try {
+            while (size == capacity) {
+                notFull.await();
+            }
+
+            enqueueOne(e);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public int putAll(List<T> c) throws InterruptedException {
+        lock.lockInterruptibly();
+
+        try {
+            while (size == capacity) {
+                notFull.await();
+            }
+
+            int availableCapacity = capacity - size;
+
+            int toInsert = Math.min(availableCapacity, c.size());
+
+            int producerIdx = this.producerIdx;
+            for (int i = 0; i < toInsert; i++) {
+                data[producerIdx] = c.get(i);
+                if (++producerIdx == capacity) {
+                    producerIdx = 0;
+                }
+            }
+
+            this.producerIdx = producerIdx;
+
+            if (size == 0) {
+                notEmpty.signalAll();
+            }
+
+            size += toInsert;
+
+            return toInsert;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public void putAll(T[] a, int offset, int len) throws InterruptedException {
+        while (len > 0) {
+            int published = internalPutAll(a, offset, len);
+            offset += published;
+            len -= published;
+        }
+    }
+
+    private int internalPutAll(T[] a, int offset, int len) throws InterruptedException {
+        lock.lockInterruptibly();
+
+        try {
+            while (size == capacity) {
+                notFull.await();
+            }
+
+            int availableCapacity = capacity - size;
+            int toInsert = Math.min(availableCapacity, len);
+            int producerIdx = this.producerIdx;
+
+            // First span
+            int firstSpan = Math.min(toInsert, capacity - producerIdx);
+            System.arraycopy(a, offset, data, producerIdx, firstSpan);
+            producerIdx += firstSpan;
+
+            int secondSpan = toInsert - firstSpan;
+            if (secondSpan > 0) {
+                System.arraycopy(a, offset + firstSpan, data, 0, secondSpan);
+                producerIdx = secondSpan;
+            }
+
+            if (producerIdx == capacity) {
+                producerIdx = 0;
+            }
+
+            this.producerIdx = producerIdx;
+
+            if (size == 0) {
+                notEmpty.signalAll();
+            }
+
+            size += toInsert;
+            return toInsert;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public boolean offer(T e, long timeout, TimeUnit unit) throws InterruptedException {
+        long remainingTimeNanos = unit.toNanos(timeout);
+
+        lock.lockInterruptibly();
+        try {
+            while (size == capacity) {
+                if (remainingTimeNanos <= 0L) {
+                    return false;
+                }
+
+                remainingTimeNanos = notFull.awaitNanos(remainingTimeNanos);
+            }
+
+            enqueueOne(e);
+            return true;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public T take() throws InterruptedException {
+        lock.lockInterruptibly();
+
+        try {
+            while (size == 0) {
+                notEmpty.await();
+            }
+
+            return dequeueOne();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public T poll(long timeout, TimeUnit unit) throws InterruptedException {
+        long remainingTimeNanos = unit.toNanos(timeout);
+
+        lock.lockInterruptibly();
+        try {
+            while (size == 0) {
+                if (remainingTimeNanos <= 0L) {
+                    return null;
+                }
+
+                remainingTimeNanos = notEmpty.awaitNanos(remainingTimeNanos);
+            }
+
+            return dequeueOne();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public int remainingCapacity() {
+        return capacity - size;
+    }
+
+    @Override
+    public int drainTo(Collection<? super T> c) {
+        return drainTo(c, capacity);
+    }
+
+    @Override
+    public int drainTo(Collection<? super T> c, int maxElements) {
+        lock.lock();
+        try {
+            int toDrain = Math.min(size, maxElements);
+
+            int consumerIdx = this.consumerIdx;
+            for (int i = 0; i < toDrain; i++) {
+                T item = data[consumerIdx];
+                data[consumerIdx] = null;
+                c.add(item);
+
+                if (++consumerIdx == capacity) {
+                    consumerIdx = 0;
+                }
+            }
+
+            this.consumerIdx = consumerIdx;
+            if (size == capacity) {

Review Comment:
   If the `maxElements` is 0, we can't trigger `notFull.signalAll();`. Shall we check the `maxElements` param?



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