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From ivmaykov <...@git.apache.org>
Subject [GitHub] zookeeper pull request #680: ZOOKEEPER-3174: Quorum TLS - support reloading ...
Date Thu, 06 Dec 2018 19:58:10 GMT
Github user ivmaykov commented on a diff in the pull request:

    --- Diff: zookeeper-server/src/main/java/org/apache/zookeeper/common/FileChangeWatcher.java
    @@ -0,0 +1,253 @@
    + * 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.zookeeper.common;
    +import com.sun.nio.file.SensitivityWatchEventModifier;
    +import org.apache.zookeeper.server.ZooKeeperThread;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +import java.io.IOException;
    +import java.nio.file.ClosedWatchServiceException;
    +import java.nio.file.FileSystem;
    +import java.nio.file.Path;
    +import java.nio.file.StandardWatchEventKinds;
    +import java.nio.file.WatchEvent;
    +import java.nio.file.WatchKey;
    +import java.nio.file.WatchService;
    +import java.util.function.Consumer;
    + * Instances of this class can be used to watch a directory for file changes. When a
file is added to, deleted from,
    + * or is modified in the given directory, the callback provided by the user will be called
from a background thread.
    + * Some things to keep in mind:
    + * <ul>
    + * <li>The callback should be thread-safe.</li>
    + * <li>Changes that happen around the time the thread is started may be missed.</li>
    + * <li>There is a delay between a file changing and the callback firing.</li>
    + * <li>The watch is not recursive - changes to subdirectories will not trigger
a callback.</li>
    + * </ul>
    + */
    +public final class FileChangeWatcher {
    --- End diff --
    I prefer to use composition over inheritance in cases where inheritance is not clearly
better - it tends to avoid problems. If FileChangeWatcher extends Thread, then it will have
a "is a" relationship with Thread, and can be used anywhere a Thread is used. Since it's not
a generic Thread, it's not clear to me that this would be correct. But I don't feel too strongly
about it.


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