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From tumativ <...@git.apache.org>
Subject [GitHub] zookeeper pull request #680: ZOOKEEPER-3174: Quorum TLS - support reloading ...
Date Sat, 03 Nov 2018 00:48:57 GMT
Github user tumativ commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/680#discussion_r230539608
  
    --- Diff: zookeeper-server/src/main/java/org/apache/zookeeper/common/FileChangeWatcher.java
---
    @@ -0,0 +1,180 @@
    +/**
    + * 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 {
    +    private static final Logger LOG = LoggerFactory.getLogger(FileChangeWatcher.class);
    +
    +    private final WatcherThread watcherThread;
    +
    +    /**
    +     * Creates a watcher that watches <code>dirPath</code> and invokes <code>callback</code>
on changes.
    +     *
    +     * @param dirPath the directory to watch.
    +     * @param callback the callback to invoke with events. <code>event.kind()</code>
will return the type of event,
    +     *                 and <code>event.context()</code> will return the filename
relative to <code>dirPath</code>.
    +     * @throws IOException if there is an error creating the WatchService.
    +     */
    +    public FileChangeWatcher(Path dirPath, Consumer<WatchEvent<?>> callback)
throws IOException {
    +        FileSystem fs = dirPath.getFileSystem();
    +        WatchService watchService = fs.newWatchService();
    +        if (LOG.isDebugEnabled()) {
    +            LOG.debug("Registering with watch service: " + dirPath);
    +        }
    +        dirPath.register(
    +                watchService,
    +                new WatchEvent.Kind<?>[]{
    +                        StandardWatchEventKinds.ENTRY_CREATE,
    +                        StandardWatchEventKinds.ENTRY_DELETE,
    +                        StandardWatchEventKinds.ENTRY_MODIFY,
    +                        StandardWatchEventKinds.OVERFLOW},
    +                SensitivityWatchEventModifier.HIGH);
    +        this.watcherThread = new WatcherThread(watchService, callback);
    +        this.watcherThread.setDaemon(true);
    +        this.watcherThread.start();
    --- End diff --
    
    Thanks for defining states. 


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