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 import org.apache.commons.exec.util.DebugUtils;
022
023 /**
024 * Destroys a process running for too long. For example:
025 *
026 * <pre>
027 * ExecuteWatchdog watchdog = new ExecuteWatchdog(30000);
028 * Executer exec = new Executer(myloghandler, watchdog);
029 * exec.setCommandLine(mycmdline);
030 * int exitvalue = exec.execute();
031 * if (Execute.isFailure(exitvalue) && watchdog.killedProcess()) {
032 * // it was killed on purpose by the watchdog
033 * }
034 * </pre>
035 *
036 * When starting an asynchronous process than 'ExecuteWatchdog' is the
037 * keeper of the process handle. In some cases it is useful not to define
038 * a timeout (and pass 'INFINITE_TIMEOUT') and to kill the process explicitly
039 * using 'destroyProcess()'.
040 * <p>
041 * Please note that ExecuteWatchdog is processed asynchronously, e.g. it might
042 * be still attached to a process even after the DefaultExecutor.execute
043 * has returned.
044 *
045 * @see org.apache.commons.exec.Executor
046 * @see org.apache.commons.exec.Watchdog
047 */
048 public class ExecuteWatchdog implements TimeoutObserver {
049
050 /** The marker for an infinite timeout */
051 public static final long INFINITE_TIMEOUT = -1;
052
053 /** The process to execute and watch for duration. */
054 private Process process;
055
056 /** Is a user-supplied timeout in use */
057 private final boolean hasWatchdog;
058
059 /** Say whether or not the watchdog is currently monitoring a process. */
060 private boolean watch;
061
062 /** Exception that might be thrown during the process execution. */
063 private Exception caught;
064
065 /** Say whether or not the process was killed due to running overtime. */
066 private boolean killedProcess;
067
068 /** Will tell us whether timeout has occurred. */
069 private final Watchdog watchdog;
070
071 /**
072 * Creates a new watchdog with a given timeout.
073 *
074 * @param timeout
075 * the timeout for the process in milliseconds. It must be
076 * greater than 0 or 'INFINITE_TIMEOUT'
077 */
078 public ExecuteWatchdog(final long timeout) {
079 this.killedProcess = false;
080 this.watch = false;
081 this.hasWatchdog = (timeout != INFINITE_TIMEOUT);
082 if(this.hasWatchdog) {
083 this.watchdog = new Watchdog(timeout);
084 this.watchdog.addTimeoutObserver(this);
085 }
086 else {
087 this.watchdog = null;
088 }
089 }
090
091 /**
092 * Watches the given process and terminates it, if it runs for too long. All
093 * information from the previous run are reset.
094 *
095 * @param process
096 * the process to monitor. It cannot be <tt>null</tt>
097 * @throws IllegalStateException
098 * if a process is still being monitored.
099 */
100 public synchronized void start(final Process process) {
101 if (process == null) {
102 throw new NullPointerException("process is null.");
103 }
104 if (this.process != null) {
105 throw new IllegalStateException("Already running.");
106 }
107 this.caught = null;
108 this.killedProcess = false;
109 this.watch = true;
110 this.process = process;
111 if(this.hasWatchdog) {
112 watchdog.start();
113 }
114 }
115
116 /**
117 * Stops the watcher. It will notify all threads possibly waiting on this
118 * object.
119 */
120 public synchronized void stop() {
121 if(hasWatchdog) {
122 watchdog.stop();
123 }
124 watch = false;
125 process = null;
126 }
127
128 /**
129 * Destroys the running process manually.
130 */
131 public synchronized void destroyProcess() {
132 this.timeoutOccured(null);
133 this.stop();
134 }
135
136 /**
137 * Called after watchdog has finished.
138 */
139 public synchronized void timeoutOccured(final Watchdog w) {
140 try {
141 try {
142 // We must check if the process was not stopped
143 // before being here
144 if(process != null) {
145 process.exitValue();
146 }
147 } catch (IllegalThreadStateException itse) {
148 // the process is not terminated, if this is really
149 // a timeout and not a manual stop then destroy it.
150 if (watch) {
151 killedProcess = true;
152 process.destroy();
153 }
154 }
155 } catch (Exception e) {
156 caught = e;
157 DebugUtils.handleException("Getting the exit value of the process failed", e);
158 } finally {
159 cleanUp();
160 }
161 }
162
163
164 /**
165 * This method will rethrow the exception that was possibly caught during
166 * the run of the process. It will only remains valid once the process has
167 * been terminated either by 'error', timeout or manual intervention.
168 * Information will be discarded once a new process is ran.
169 *
170 * @throws Exception
171 * a wrapped exception over the one that was silently swallowed
172 * and stored during the process run.
173 */
174 public synchronized void checkException() throws Exception {
175 if (caught != null) {
176 throw caught;
177 }
178 }
179
180 /**
181 * Indicates whether or not the watchdog is still monitoring the process.
182 *
183 * @return <tt>true</tt> if the process is still running, otherwise
184 * <tt>false</tt>.
185 */
186 public synchronized boolean isWatching() {
187 return watch;
188 }
189
190 /**
191 * Indicates whether the last process run was killed.
192 *
193 * @return <tt>true</tt> if the process was killed
194 * <tt>false</tt>.
195 */
196 public synchronized boolean killedProcess() {
197 return killedProcess;
198 }
199
200 /**
201 * reset the monitor flag and the process.
202 */
203 protected synchronized void cleanUp() {
204 watch = false;
205 process = null;
206 }
207 }