shayshim commented on a change in pull request #335: [CURATOR-549] Recipes based on Persistent Recursive Watchers URL: https://github.com/apache/curator/pull/335#discussion_r399259021
########## File path: curator-recipes/src/main/java/org/apache/curator/framework/recipes/cache/CuratorCache.java ########## @@ -0,0 +1,127 @@ +/** + * 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.curator.framework.recipes.cache; + +import org.apache.curator.framework.CuratorFramework; +import org.apache.curator.framework.listen.Listenable; +import java.io.Closeable; +import java.util.Optional; +import java.util.stream.Stream; + +/** + * <p> + * A utility that attempts to keep the data from a node locally cached. Optionally the entire + * tree of children below the node can also be cached. Will respond to update/create/delete events, pull + * down the data, etc. You can register listeners that will get notified when changes occur. + * </p> + * + * <p> + * <b>IMPORTANT</b> - it's not possible to stay transactionally in sync. Users of this class must Review comment: This comment was never very clear to me, and if it is not only me, maybe it is good opportunity to rephrase it or give more details. By "false positive" here do you mean that we might get events that do not reflect anymore the latest state of the zknode? These events are still true, just a bit late. Soon there should follow the subsequent events until latest state is reflected. This behavior is general in ZK clients, not just the cache. By "false negative" do you mean that we can miss events because ZK only sends the latest event (e.g. while cache might have been disconnected for a while, missing some zknode events)? Again, I feel like it is true for any ZK client, not just the cache. Though in Persistent Watchers I guess we potentially miss less momentarily events, because the Watcher is always there. ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
