org.apache.spark.util.SignalUtils.scala Maven / Gradle / Ivy
/*
* 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.spark.util
import java.util.Collections
import scala.collection.JavaConverters._
import org.apache.commons.lang3.SystemUtils
import org.slf4j.Logger
import sun.misc.{Signal, SignalHandler}
import org.apache.spark.internal.Logging
/**
* Contains utilities for working with posix signals.
*/
private[spark] object SignalUtils extends Logging {
/** A flag to make sure we only register the logger once. */
private var loggerRegistered = false
/** Register a signal handler to log signals on UNIX-like systems. */
def registerLogger(log: Logger): Unit = synchronized {
if (!loggerRegistered) {
Seq("TERM", "HUP", "INT").foreach { sig =>
SignalUtils.register(sig) {
log.error("RECEIVED SIGNAL " + sig)
false
}
}
loggerRegistered = true
}
}
/**
* Adds an action to be run when a given signal is received by this process.
*
* Note that signals are only supported on unix-like operating systems and work on a best-effort
* basis: if a signal is not available or cannot be intercepted, only a warning is emitted.
*
* All actions for a given signal are run in a separate thread.
*/
def register(signal: String)(action: => Boolean): Unit = synchronized {
if (SystemUtils.IS_OS_UNIX) {
try {
val handler = handlers.getOrElseUpdate(signal, {
logInfo("Registered signal handler for " + signal)
new ActionHandler(new Signal(signal))
})
handler.register(action)
} catch {
case ex: Exception => logWarning(s"Failed to register signal handler for " + signal, ex)
}
}
}
/**
* A handler for the given signal that runs a collection of actions.
*/
private class ActionHandler(signal: Signal) extends SignalHandler {
/**
* List of actions upon the signal; the callbacks should return true if the signal is "handled",
* i.e. should not escalate to the next callback.
*/
private val actions = Collections.synchronizedList(new java.util.LinkedList[() => Boolean])
// original signal handler, before this handler was attached
private val prevHandler: SignalHandler = Signal.handle(signal, this)
/**
* Called when this handler's signal is received. Note that if the same signal is received
* before this method returns, it is escalated to the previous handler.
*/
override def handle(sig: Signal): Unit = {
// register old handler, will receive incoming signals while this handler is running
Signal.handle(signal, prevHandler)
// Run all actions, escalate to parent handler if no action catches the signal
// (i.e. all actions return false). Note that calling `map` is to ensure that
// all actions are run, `forall` is short-circuited and will stop evaluating
// after reaching a first false predicate.
val escalate = actions.asScala.map(action => action()).forall(_ == false)
if (escalate) {
prevHandler.handle(sig)
}
// re-register this handler
Signal.handle(signal, this)
}
/**
* Adds an action to be run by this handler.
* @param action An action to be run when a signal is received. Return true if the signal
* should be stopped with this handler, false if it should be escalated.
*/
def register(action: => Boolean): Unit = actions.add(() => action)
}
/** Mapping from signal to their respective handlers. */
private val handlers = new scala.collection.mutable.HashMap[String, ActionHandler]
}