    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    }