Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/12557#discussion_r60699342
--- Diff: core/src/main/scala/org/apache/spark/util/Signaling.scala ---
@@ -0,0 +1,99 @@
+/*
+ * 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, LinkedList}
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable.HashMap
+
+import org.apache.commons.lang3.SystemUtils
+import sun.misc.{Signal, SignalHandler}
+
+import org.apache.spark.internal.Logging
+
+
+/**
+ * Contains utilities for working with posix signals.
+ */
+private[spark] object Signaling extends Logging {
+
+ /**
+ * A handler for the given signal that runs a collection of actions.
+ */
+ private class ActionHandler(signal: Signal) extends SignalHandler {
+
+ private val actions = Collections.synchronizedList(new 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)
+
+ val escalate = actions.asScala forall { action =>
+ !action()
+ }
+
+ if(escalate) {
+ prevHandler.handle(sig)
+ }
+
+ // re-register this handler
+ Signal.handle(signal, this)
+ }
+
+ /**
+ * Add 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)
+
+ }
+
+ // contains association of signals to their respective handlers
+ private val handlers = new HashMap[String, ActionHandler]
+
+ /**
+ * 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 {
--- End diff --
this is a really weird style for spark
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