001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    package org.apache.hadoop.util;
019    
020    import org.apache.commons.logging.Log;
021    import org.apache.commons.logging.LogFactory;
022    import org.apache.hadoop.classification.InterfaceAudience;
023    import org.apache.hadoop.classification.InterfaceStability;
024    
025    /**
026     * Facilitates hooking process termination for tests and debugging.
027     */
028    @InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
029    @InterfaceStability.Unstable
030    public final class ExitUtil {
031      private final static Log LOG = LogFactory.getLog(ExitUtil.class.getName());
032      private static volatile boolean systemExitDisabled = false;
033      private static volatile ExitException firstExitException;
034    
035      public static class ExitException extends RuntimeException {
036        private static final long serialVersionUID = 1L;
037        public final int status;
038    
039        public ExitException(int status, String msg) {
040          super(msg);
041          this.status = status;
042        }
043      }
044    
045      /**
046       * Disable the use of System.exit for testing.
047       */
048      public static void disableSystemExit() {
049        systemExitDisabled = true;
050      }
051    
052      /**
053       * @return true if terminate has been called
054       */
055      public static boolean terminateCalled() {
056        // Either we set this member or we actually called System#exit
057        return firstExitException != null;
058      }
059    
060      /**
061       * @return the first ExitException thrown, null if none thrown yet
062       */
063      public static ExitException getFirstExitException() {
064        return firstExitException;
065      }
066    
067      /**
068       * Reset the tracking of process termination. This is for use
069       * in unit tests where one test in the suite expects an exit
070       * but others do not.
071       */
072      public static void resetFirstExitException() {
073        firstExitException = null;
074      }
075    
076      /**
077       * Terminate the current process. Note that terminate is the *only* method
078       * that should be used to terminate the daemon processes.
079       * @param status exit code
080       * @param msg message used to create the ExitException
081       * @throws ExitException if System.exit is disabled for test purposes
082       */
083      public static void terminate(int status, String msg) throws ExitException {
084        LOG.info("Exiting with status " + status);
085        if (systemExitDisabled) {
086          ExitException ee = new ExitException(status, msg);
087          LOG.fatal("Terminate called", ee);
088          if (null == firstExitException) {
089            firstExitException = ee;
090          }
091          throw ee;
092        }
093        System.exit(status);
094      }
095    
096      /**
097       * Like {@link terminate(int, String)} but uses the given throwable to
098       * initialize the ExitException.
099       * @param status
100       * @param t throwable used to create the ExitException
101       * @throws ExitException if System.exit is disabled for test purposes
102       */
103      public static void terminate(int status, Throwable t) throws ExitException {
104        terminate(status, StringUtils.stringifyException(t));
105      }
106    
107      /**
108       * Like {@link terminate(int, String)} without a message.
109       * @param status
110       * @throws ExitException if System.exit is disabled for test purposes
111       */
112      public static void terminate(int status) throws ExitException {
113        terminate(status, "ExitException");
114      }
115    }