/**
* 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());
}
}