001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 *
017 */
018
019 package org.apache.commons.exec;
020
021 /**
022 * Destroys a process running for too long. For example:
023 *
024 * <pre>
025 * ExecuteWatchdog watchdog = new ExecuteWatchdog(30000);
026 * Execute exec = new Execute(myloghandler, watchdog);
027 * exec.setCommandLine(mycmdline);
028 * int exitvalue = exec.execute();
029 * if (Execute.isFailure(exitvalue) && watchdog.killedProcess()) {
030 * // it was killed on purpose by the watchdog
031 * }
032 * </pre>
033 *
034 * @see org.apache.commons.exec.Executor
035 * @see org.apache.commons.exec.Watchdog
036 */
037 public class ExecuteWatchdog implements TimeoutObserver {
038
039 /** The process to execute and watch for duration. */
040 private Process process;
041
042 /** Say whether or not the watchdog is currently monitoring a process. */
043 private boolean watch;
044
045 /** Exception that might be thrown during the process execution. */
046 private Exception caught;
047
048 /** Say whether or not the process was killed due to running overtime. */
049 private boolean killedProcess;
050
051 /** Will tell us whether timeout has occurred. */
052 private final Watchdog watchdog;
053
054 /**
055 * Creates a new watchdog with a given timeout.
056 *
057 * @param timeout
058 * the timeout for the process in milliseconds. It must be
059 * greater than 0.
060 */
061 public ExecuteWatchdog(final long timeout) {
062 this.killedProcess = false;
063 this.watch = false;
064 this.watchdog = new Watchdog(timeout);
065 this.watchdog.addTimeoutObserver(this);
066 }
067
068 /**
069 * Watches the given process and terminates it, if it runs for too long. All
070 * information from the previous run are reset.
071 *
072 * @param process
073 * the process to monitor. It cannot be <tt>null</tt>
074 * @throws IllegalStateException
075 * if a process is still being monitored.
076 */
077 public synchronized void start(final Process process) {
078 if (process == null) {
079 throw new NullPointerException("process is null.");
080 }
081 if (this.process != null) {
082 throw new IllegalStateException("Already running.");
083 }
084 this.caught = null;
085 this.killedProcess = false;
086 this.watch = true;
087 this.process = process;
088 watchdog.start();
089 }
090
091 /**
092 * Stops the watcher. It will notify all threads possibly waiting on this
093 * object.
094 */
095 public synchronized void stop() {
096 watchdog.stop();
097 watch = false;
098 process = null;
099 }
100
101 /**
102 * Destroys the running process manually.
103 */
104 public synchronized void destroyProcess() {
105 this.timeoutOccured(new Watchdog(1));
106 this.stop();
107 }
108
109 /**
110 * Called after watchdog has finished.
111 */
112 public synchronized void timeoutOccured(final Watchdog w) {
113 try {
114 try {
115 // We must check if the process was not stopped
116 // before being here
117 if(process != null) {
118 process.exitValue();
119 }
120 } catch (IllegalThreadStateException itse) {
121 // the process is not terminated, if this is really
122 // a timeout and not a manual stop then destroy it.
123 if (watch) {
124 killedProcess = true;
125 process.destroy();
126 }
127 }
128 } catch (Exception e) {
129 caught = e;
130 } finally {
131 cleanUp();
132 }
133 }
134
135
136 /**
137 * This method will rethrow the exception that was possibly caught during
138 * the run of the process. It will only remains valid once the process has
139 * been terminated either by 'error', timeout or manual intervention.
140 * Information will be discarded once a new process is ran.
141 *
142 * @throws Exception
143 * a wrapped exception over the one that was silently swallowed
144 * and stored during the process run.
145 */
146 public synchronized void checkException() throws Exception {
147 if (caught != null) {
148 throw caught;
149 }
150 }
151
152 /**
153 * Indicates whether or not the watchdog is still monitoring the process.
154 *
155 * @return <tt>true</tt> if the process is still running, otherwise
156 * <tt>false</tt>.
157 */
158 public synchronized boolean isWatching() {
159 return watch;
160 }
161
162 /**
163 * Indicates whether the last process run was killed.
164 *
165 * @return <tt>true</tt> if the process was killed
166 * <tt>false</tt>.
167 */
168 public synchronized boolean killedProcess() {
169 return killedProcess;
170 }
171
172 /**
173 * reset the monitor flag and the process.
174 */
175 protected synchronized void cleanUp() {
176 watch = false;
177 process = null;
178 }
179 }