HADOOP-9318. When exiting on a signal, print the signal name first. Contributed by Colin Patrick McCabe.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1457124 13f79535-47bb-0310-9956-ffa450edef68

dev-support/test-patch.properties

@@ -18,4 +18,4 @@
 
 OK_RELEASEAUDIT_WARNINGS=0
 OK_FINDBUGS_WARNINGS=0
-OK_JAVADOC_WARNINGS=8
+OK_JAVADOC_WARNINGS=13

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -25,6 +25,9 @@ Release 2.0.5-beta - UNRELEASED
 
     HADOOP-9343. Allow additional exceptions through the RPC layer. (sseth)
 
+    HADOOP-9318. When exiting on a signal, print the signal name first. (Colin
+    Patrick McCabe via atm)
+
   OPTIMIZATIONS
 
   BUG FIXES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/SignalLogger.java

@@ -0,0 +1,93 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.util;
+
+import sun.misc.Signal;
+import sun.misc.SignalHandler;
+
+import org.apache.commons.logging.Log;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+
+/**
+ * This class logs a message whenever we're about to exit on a UNIX signal.
+ * This is helpful for determining the root cause of a process' exit.
+ * For example, if the process exited because the system administrator 
+ * ran a standard "kill," you would see 'EXITING ON SIGNAL SIGTERM' in the log.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Unstable
+public enum SignalLogger {
+  INSTANCE;
+
+  private boolean registered = false;
+
+  /**
+   * Our signal handler.
+   */
+  private static class Handler implements SignalHandler {
+    final private org.apache.commons.logging.Log LOG;
+    final private SignalHandler prevHandler;
+
+    Handler(String name, Log LOG) {
+      this.LOG = LOG;
+      prevHandler = Signal.handle(new Signal(name), this);
+    }
+
+    /**
+     * Handle an incoming signal.
+     *
+     * @param signal    The incoming signal
+     */
+    @Override
+    public void handle(Signal signal) {
+      LOG.error("RECEIVED SIGNAL " + signal.getNumber() +
+          ": SIG" + signal.getName());
+      prevHandler.handle(signal);
+    }
+  }
+
+  /**
+   * Register some signal handlers.
+   *
+   * @param LOG        The log4j logfile to use in the signal handlers.
+   */
+  public void register(final Log LOG) {
+    if (registered) {
+      throw new IllegalStateException("Can't re-install the signal handlers.");
+    }
+    registered = true;
+    StringBuilder bld = new StringBuilder();
+    bld.append("registered UNIX signal handlers for [");
+    final String SIGNALS[] = { "TERM", "HUP", "INT" };
+    String separator = "";
+    for (String signalName : SIGNALS) {
+      try {
+        new Handler(signalName, LOG);
+        bld.append(separator);
+        bld.append(signalName);
+        separator = ", ";
+      } catch (Exception e) {
+        LOG.debug(e);
+      }
+    }
+    bld.append("]");
+    LOG.info(bld.toString());
+  }
+}

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/StringUtils.java

@@ -32,6 +32,7 @@ import java.util.List;
 import java.util.Locale;
 import java.util.StringTokenizer;
 
+import org.apache.commons.lang.SystemUtils;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.fs.Path;
@@ -588,6 +589,13 @@ public class StringUtils {
         )
       );
 
+    if (SystemUtils.IS_OS_UNIX) {
+      try {
+        SignalLogger.INSTANCE.register(LOG);
+      } catch (Throwable t) {
+        LOG.warn("failed to register any UNIX signal loggers: ", t);
+      }
+    }
     ShutdownHookManager.get().addShutdownHook(
       new Runnable() {
         @Override

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestSignalLogger.java

@@ -0,0 +1,42 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.util;
+
+import org.apache.commons.lang.SystemUtils;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.junit.Assert;
+import org.junit.Assume;
+import org.junit.Test;
+
+public class TestSignalLogger {
+  public static final Log LOG = LogFactory.getLog(TestSignalLogger.class);
+  
+  @Test(timeout=60000)
+  public void testInstall() throws Exception {
+    Assume.assumeTrue(SystemUtils.IS_OS_UNIX);
+    SignalLogger.INSTANCE.register(LOG);
+    try {
+      SignalLogger.INSTANCE.register(LOG);
+      Assert.fail("expected IllegalStateException from double registration");
+    } catch (IllegalStateException e) {
+      // fall through
+    }
+  }
+}