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[broker] register loadbalance znode should attempt to wait until sess…
…ion expired (apache#6788) *Motivation* Exceptions `Broker-znode owned by different zk-session` is commonly seen when a broker starts up in Kubernetes environment. That's because the previous znode is not expired.
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pulsar-zookeeper-utils/src/main/java/org/apache/pulsar/zookeeper/ZkUtils.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. | ||
| */ | ||
| package org.apache.pulsar.zookeeper; | ||
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| import java.util.concurrent.CountDownLatch; | ||
| import java.util.concurrent.TimeUnit; | ||
| import org.apache.zookeeper.KeeperException; | ||
| import org.apache.zookeeper.KeeperException.NodeExistsException; | ||
| import org.apache.zookeeper.Watcher; | ||
| import org.apache.zookeeper.Watcher.Event.EventType; | ||
| import org.apache.zookeeper.ZooKeeper; | ||
| import org.apache.zookeeper.data.Stat; | ||
| import org.slf4j.Logger; | ||
| import org.slf4j.LoggerFactory; | ||
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|
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| /** | ||
| * ZooKeeper utils. | ||
| */ | ||
| public final class ZkUtils { | ||
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|
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| private static final Logger log = LoggerFactory.getLogger(ZkUtils.class); | ||
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| /** | ||
| * Check if the provided <i>path</i> exists or not and wait it expired if possible. | ||
| * | ||
| * @param zk the zookeeper client instance | ||
| * @param path the zookeeper path | ||
| * @param sessionTimeoutMs session timeout in milliseconds | ||
| * @return true if path exists, otherwise return false | ||
| * @throws KeeperException when failed to access zookeeper | ||
| * @throws InterruptedException interrupted when waiting for znode to be expired | ||
| */ | ||
| public static boolean checkNodeAndWaitExpired(ZooKeeper zk, | ||
| String path, | ||
| long sessionTimeoutMs) throws KeeperException, InterruptedException { | ||
| final CountDownLatch prevNodeLatch = new CountDownLatch(1); | ||
| Watcher zkPrevNodeWatcher = watchedEvent -> { | ||
| // check for prev node deletion. | ||
| if (EventType.NodeDeleted == watchedEvent.getType()) { | ||
| prevNodeLatch.countDown(); | ||
| } | ||
| }; | ||
| Stat stat = zk.exists(path, zkPrevNodeWatcher); | ||
| if (null != stat) { | ||
| // if the ephemeral owner isn't current zookeeper client | ||
| // wait for it to be expired | ||
| if (stat.getEphemeralOwner() != zk.getSessionId()) { | ||
| log.info("Previous znode : {} still exists, so waiting {} ms for znode deletion", | ||
| path, sessionTimeoutMs); | ||
| if (!prevNodeLatch.await(sessionTimeoutMs, TimeUnit.MILLISECONDS)) { | ||
| throw new NodeExistsException(path); | ||
| } else { | ||
| return false; | ||
| } | ||
| } | ||
| return true; | ||
| } else { | ||
| return false; | ||
| } | ||
| } | ||
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| } |