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) &amp;&amp; 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    }