| /* |
| * |
| * * 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.ambari.server.configuration; |
| |
| import java.io.File; |
| import java.util.function.Consumer; |
| |
| import org.apache.log4j.helpers.FileWatchdog; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * Watchdog that notifies a listener on a file content change. |
| */ |
| public class SingleFileWatch { |
| private static final Logger LOG = LoggerFactory.getLogger(SingleFileWatch.class); |
| private final File file; |
| private final FileWatchdog watchdog; |
| private final Consumer<File> changeListener; |
| private volatile boolean started = false; |
| |
| /** |
| * @param file to be watched |
| * @param changeListener to be notified if the file content changes |
| */ |
| public SingleFileWatch(File file, Consumer<File> changeListener) { |
| this.file = file; |
| this.changeListener = changeListener; |
| this.watchdog = createWatchDog(); |
| } |
| |
| private FileWatchdog createWatchDog() { |
| FileWatchdog fileWatch = new FileWatchdog(file.getAbsolutePath()) { |
| @Override |
| protected void doOnChange() { |
| if (started) { |
| notifyListener(); |
| } |
| } |
| }; |
| fileWatch.setDelay(1000); |
| fileWatch.setDaemon(true); |
| fileWatch.setName("FileWatchdog:" + file.getName()); |
| return fileWatch; |
| } |
| |
| private void notifyListener() { |
| LOG.info("{} changed. Sending notification.", file); |
| try { |
| changeListener.accept(file); |
| } catch (Exception e) { |
| LOG.warn("Error while notifying " + this + " listener", e); |
| } |
| } |
| |
| /** |
| * Start the watch service in the background |
| */ |
| public void start() { |
| LOG.info("Starting " + this); |
| started = true; |
| watchdog.start(); |
| } |
| |
| /** |
| * Stop the watch service |
| */ |
| public void stop() { |
| LOG.info("Stopping " + this); |
| started = false; |
| watchdog.interrupt(); |
| } |
| |
| public String toString() { |
| return "SingleFileWatcher:" + file.getName(); |
| } |
| } |