Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/16189#discussion_r91671465
--- Diff: core/src/main/scala/org/apache/spark/executor/Executor.scala ---
@@ -432,6 +435,57 @@ private[spark] class Executor(
}
/**
+ * Supervises the killing / cancellation of a task by sending the
interrupted flag, optionally
+ * sending a Thread.interrupt(), and monitoring the task until it
finishes.
+ */
+ private class TaskReaper(taskRunner: TaskRunner, interruptThread:
Boolean) extends Runnable {
+
+ private[this] val killPollingFrequencyMs: Long =
+ conf.getTimeAsMs("spark.task.killPollingFrequency", "10s")
+
+ private[this] val killTimeoutMs: Long =
conf.getTimeAsMs("spark.task.killTimeout", "2m")
+
+ private[this] val takeThreadDump: Boolean =
+ conf.getBoolean("spark.task.threadDumpKilledTasks", true)
+
+ override def run(): Unit = {
+ val startTimeMs = System.currentTimeMillis()
+ def elapsedTimeMs = System.currentTimeMillis() - startTimeMs
+
+ while (!taskRunner.isFinished && elapsedTimeMs < killTimeoutMs) {
+ taskRunner.kill(interruptThread = interruptThread)
+ taskRunner.synchronized {
+ Thread.sleep(killPollingFrequencyMs)
+ }
+ if (!taskRunner.isFinished) {
+ logWarning(s"Killed task ${taskRunner.taskId} is still running
after $elapsedTimeMs ms")
+ if (takeThreadDump) {
+ try {
+ val threads = Utils.getThreadDump()
+ threads.find(_.threadName == taskRunner.threadName).foreach
{ thread =>
+ logWarning(s"Thread dump from task
${taskRunner.taskId}:\n${thread.stackTrace}")
+ }
+ } catch {
+ case NonFatal(e) =>
+ logWarning("Exception thrown while obtaining thread dump:
", e)
+ }
+ }
+ }
+ }
+ if (!taskRunner.isFinished && killTimeoutMs > 0 && elapsedTimeMs >
killTimeoutMs) {
--- End diff --
I thought about this and it seems like there are only two possibilities
here:
1. We're running in local mode, in which case we don't actually want to
throw an exception to kill the JVM and even if we did throw then it would keep
on running because there's not an uncaught exception handler here.
2. We're running in a separate JVM, in which case any exception thrown in
this thread and not caught will cause the JVM to exit. The only place in the
body of this code that might actually throw unexpected exceptions is the
taskThreadDump, which is already in a `try-catch` block to prevent exceptions
from bubbling up.
Thus the only purpose of a finally block would be to detect whether it was
reached via an exception patch and to log a warning to state that task kill
progress will no longer be monitored. Basically, I'm not sure what the finally
block is buying us in terms of actionable / useful logs and it's only going to
add complexity because then we need to be careful to not throw from the finally
block in case it was entered via an exception, etc.
---
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