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Cherry-pick and adapt ZOOKEEPER-2260 for getChildren pagination (#5)
Apply the patch of ZOOKEEPER-2260: paginated getChildren call (apache#50) And adjust code style to pass the check style verification Credit goest to the original author of ZOOKEEPER-2260
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101 changes: 101 additions & 0 deletions
101
zookeeper-server/src/main/java/org/apache/zookeeper/ChildrenBatchIterator.java
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| /** | ||
| * 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. | ||
| */ | ||
|
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| package org.apache.zookeeper; | ||
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| import java.util.LinkedList; | ||
| import java.util.List; | ||
| import java.util.NoSuchElementException; | ||
| import org.apache.zookeeper.data.PathWithStat; | ||
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| /** | ||
| * Iterator over children nodes of a given path. | ||
| */ | ||
| class ChildrenBatchIterator implements RemoteIterator<PathWithStat> { | ||
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| private final ZooKeeper zooKeeper; | ||
| private final String path; | ||
| private final Watcher watcher; | ||
| private final int batchSize; | ||
| private final LinkedList<PathWithStat> childrenQueue; | ||
| private long nextBatchMinZxid; | ||
| private int nextBatchZxidOffset; | ||
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| ChildrenBatchIterator(ZooKeeper zooKeeper, String path, Watcher watcher, int batchSize, long minZxid) | ||
| throws KeeperException, InterruptedException { | ||
| this.zooKeeper = zooKeeper; | ||
| this.path = path; | ||
| this.watcher = watcher; | ||
| this.batchSize = batchSize; | ||
| this.nextBatchZxidOffset = 0; | ||
| this.nextBatchMinZxid = minZxid; | ||
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| this.childrenQueue = new LinkedList<>(); | ||
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| List<PathWithStat> firstChildrenBatch = zooKeeper.getChildren(path, watcher, batchSize, nextBatchMinZxid, nextBatchZxidOffset); | ||
| childrenQueue.addAll(firstChildrenBatch); | ||
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| updateOffsetsForNextBatch(firstChildrenBatch); | ||
| } | ||
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| @Override | ||
| public boolean hasNext() { | ||
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| // next() never lets childrenQueue empty unless we iterated over all children | ||
| return !childrenQueue.isEmpty(); | ||
| } | ||
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| @Override | ||
| public PathWithStat next() throws KeeperException, InterruptedException, NoSuchElementException { | ||
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| if (!hasNext()) { | ||
| throw new NoSuchElementException("No more children"); | ||
| } | ||
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| // If we're down to the last element, backfill before returning it | ||
| if (childrenQueue.size() == 1) { | ||
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| List<PathWithStat> childrenBatch = zooKeeper.getChildren(path, watcher, batchSize, nextBatchMinZxid, nextBatchZxidOffset); | ||
| childrenQueue.addAll(childrenBatch); | ||
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| updateOffsetsForNextBatch(childrenBatch); | ||
| } | ||
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| PathWithStat returnChildren = childrenQueue.pop(); | ||
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| return returnChildren; | ||
| } | ||
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| /** | ||
| * Prepare minZxid and zkidOffset for the next batch request based on the children returned in the current | ||
| */ | ||
| private void updateOffsetsForNextBatch(List<PathWithStat> children) { | ||
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| for (PathWithStat child : children) { | ||
| long childZxid = child.getStat().getCzxid(); | ||
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| if (nextBatchMinZxid == childZxid) { | ||
| ++nextBatchZxidOffset; | ||
| } else { | ||
| nextBatchZxidOffset = 1; | ||
| nextBatchMinZxid = childZxid; | ||
| } | ||
| } | ||
| } | ||
| } |
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42
zookeeper-server/src/main/java/org/apache/zookeeper/RemoteIterator.java
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,42 @@ | ||
| /** | ||
| * 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. | ||
| */ | ||
|
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| package org.apache.zookeeper; | ||
|
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| import java.util.NoSuchElementException; | ||
|
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| /** | ||
| * An iterator over a collection whose elements need to be fetched remotely. | ||
| */ | ||
| public interface RemoteIterator<E> { | ||
|
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| /** | ||
| * Returns true if the iterator has more elements. | ||
| * @return true if the iterator has more elements, false otherwise. | ||
| */ | ||
| boolean hasNext(); | ||
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| /** | ||
| * Returns the next element in the iteration. | ||
| * @return the next element in the iteration. | ||
| * @throws InterruptedException if the thread is interrupted | ||
| * @throws KeeperException if an error is encountered server-side | ||
| * @throws NoSuchElementException if the iteration has no more elements | ||
| */ | ||
| E next() throws InterruptedException, KeeperException, NoSuchElementException; | ||
| } |
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