From dev-return-75464-archive-asf-public=cust-asf.ponee.io@zookeeper.apache.org Sun Nov 4 04:46:28 2018 Return-Path: X-Original-To: archive-asf-public@cust-asf.ponee.io Delivered-To: archive-asf-public@cust-asf.ponee.io Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by mx-eu-01.ponee.io (Postfix) with SMTP id BAF7E18066B for ; Sun, 4 Nov 2018 04:46:27 +0100 (CET) Received: (qmail 41422 invoked by uid 500); 4 Nov 2018 03:46:26 -0000 Mailing-List: contact dev-help@zookeeper.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: dev@zookeeper.apache.org Delivered-To: mailing list dev@zookeeper.apache.org Received: (qmail 41411 invoked by uid 99); 4 Nov 2018 03:46:25 -0000 Received: from git1-us-west.apache.org (HELO git1-us-west.apache.org) (140.211.11.23) by apache.org (qpsmtpd/0.29) with ESMTP; Sun, 04 Nov 2018 03:46:25 +0000 Received: by git1-us-west.apache.org (ASF Mail Server at git1-us-west.apache.org, from userid 33) id 7D54ADFE14; Sun, 4 Nov 2018 03:46:25 +0000 (UTC) From: ivmaykov To: dev@zookeeper.apache.org Reply-To: dev@zookeeper.apache.org References: In-Reply-To: Subject: [GitHub] zookeeper pull request #680: ZOOKEEPER-3174: Quorum TLS - support reloading ... Content-Type: text/plain Message-Id: <20181104034625.7D54ADFE14@git1-us-west.apache.org> Date: Sun, 4 Nov 2018 03:46:25 +0000 (UTC) Github user ivmaykov commented on a diff in the pull request: https://github.com/apache/zookeeper/pull/680#discussion_r230574766 --- Diff: zookeeper-server/src/main/java/org/apache/zookeeper/common/FileChangeWatcher.java --- @@ -0,0 +1,191 @@ +/** + * 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: + *
    + *
  • The callback should be thread-safe.
    • + *
  • Changes that happen around the time the thread is started may be missed.
    • + *
  • There is a delay between a file changing and the callback firing.
    • + *
  • The watch is not recursive - changes to subdirectories will not trigger a callback.
    • + *
+ */ +public final class FileChangeWatcher { + private static final Logger LOG = LoggerFactory.getLogger(FileChangeWatcher.class); + + public enum State { + NEW, // object created but start() not called yet + STARTING, // start() called but background thread has not entered main loop + RUNNING, // background thread is running + STOPPING, // stop() called but background thread has not exited main loop + STOPPED // stop() called and background thread has exited, or background thread crashed + } + + private final WatcherThread watcherThread; + private State state; // protected by synchronized(this) + + /** + * Creates a watcher that watches dirPath and invokes callback on changes. + * + * @param dirPath the directory to watch. + * @param callback the callback to invoke with events. event.kind() will return the type of event, + * and event.context() will return the filename relative to dirPath. + * @throws IOException if there is an error creating the WatchService. + */ + public FileChangeWatcher(Path dirPath, Consumer> 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); + state = State.NEW; + this.watcherThread = new WatcherThread(watchService, callback); + this.watcherThread.setDaemon(true); + } + + public synchronized State getState() { --- End diff -- I agree, there are use cases where a R/W lock is a great choice, but I don't think this is one of them. ---