linxiaokun528 commented on code in PR #4577: URL: https://github.com/apache/solr/pull/4577#discussion_r3555935729
########## solr/solrj-zookeeper/src/java/org/apache/solr/common/cloud/SolrCuratorEvent.java: ########## @@ -0,0 +1,62 @@ +/* + * 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.solr.common.cloud; + +import java.util.concurrent.atomic.AtomicBoolean; +import org.apache.curator.framework.CuratorFramework; +import org.apache.curator.framework.state.ConnectionState; +import org.apache.curator.framework.state.ConnectionStateListener; + +public enum SolrCuratorEvent { + // Only triggered after resume from expiration + EXPIRED_RECONNECTION { + @Override + public ConnectionStateListener of(EventAction action) { + return new ConnectionStateListener() { + private final AtomicBoolean isExpired = new AtomicBoolean(false); + + @Override + public void stateChanged(CuratorFramework client, ConnectionState newState) { + if (newState == ConnectionState.LOST) { + isExpired.set(true); + } else if (newState == ConnectionState.RECONNECTED) { + if (isExpired.compareAndSet(true, false)) { + action.respond(); + } + } + } + }; + } + }, + + SESSION_EXPIRATION { Review Comment: Great information! Thanks a lot. And you make me realize that even with the native zookeeper client, after an `Watcher.Event.KeeperState.Expired` event is received, the ephemeral nodes may still exists. Technically, the workflow should be like the following [Session Expiration Triggered] │ ▼ 1. The Leader node initiates a transaction proposal to delete the ephemeral nodes. │ ▼ 2. The proposal is broadcasted across the cluster and confirmed by a quorum of nodes. │ ▼ 3. Each Follower node commits the transaction locally, deleting the ephemeral nodes from memory. When Solr receives the Expired event, the ephemeral nodes might not have been deleted yet due to propagation delay within the ZooKeeper cluster. Therefore, we need to do some defensive programming. -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
