| /** |
| * 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.hadoop.yarn.server.nodemanager.util; |
| |
| import java.io.BufferedReader; |
| import java.io.File; |
| import java.io.FileReader; |
| import java.io.IOException; |
| |
| import org.apache.commons.logging.Log; |
| import org.apache.commons.logging.LogFactory; |
| import org.apache.hadoop.fs.Path; |
| |
| /** |
| * Helper functionality to read the pid from a file. |
| */ |
| public class ProcessIdFileReader { |
| |
| private static final Log LOG = LogFactory.getLog(ProcessIdFileReader.class); |
| |
| /** |
| * Get the process id from specified file path. |
| * Parses each line to find a valid number |
| * and returns the first one found. |
| * @return Process Id if obtained from path specified else null |
| * @throws IOException |
| */ |
| public static String getProcessId(Path path) throws IOException { |
| if (path == null) { |
| throw new IOException("Trying to access process id from a null path"); |
| } |
| |
| LOG.debug("Accessing pid from pid file " + path); |
| String processId = null; |
| FileReader fileReader = null; |
| BufferedReader bufReader = null; |
| |
| try { |
| File file = new File(path.toString()); |
| if (file.exists()) { |
| fileReader = new FileReader(file); |
| bufReader = new BufferedReader(fileReader); |
| while (true) { |
| String line = bufReader.readLine(); |
| if (line == null) { |
| break; |
| } |
| String temp = line.trim(); |
| if (!temp.isEmpty()) { |
| try { |
| Long pid = Long.valueOf(temp); |
| if (pid > 0) { |
| processId = temp; |
| break; |
| } |
| } catch (Exception e) { |
| // do nothing |
| } |
| } |
| } |
| } |
| } finally { |
| if (fileReader != null) { |
| fileReader.close(); |
| } |
| if (bufReader != null) { |
| bufReader.close(); |
| } |
| } |
| LOG.debug("Got pid " |
| + (processId != null? processId : "null") |
| + " from path " + path); |
| return processId; |
| } |
| |
| } |