Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/16189#discussion_r91672368
--- Diff: core/src/main/scala/org/apache/spark/executor/Executor.scala ---
@@ -432,6 +458,78 @@ 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,
+ val interruptThread: Boolean)
+ extends Runnable {
+
+ private[this] val taskId: Long = taskRunner.taskId
+
+ 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
+ try {
+ while (!taskRunner.isFinished && (elapsedTimeMs < killTimeoutMs ||
killTimeoutMs <= 0)) {
+ taskRunner.kill(interruptThread = interruptThread)
--- End diff --
In the case where `interruptThread = false` `taskRunner.kill()` will be
idempotent and subsequent calls won't have any effect. In the case where we
_do_ interrupt, however, the introduction of this polling loop means that we'll
interrupt the same task multiple times. Note that this could, in principle,
have happened before, but in practice I think it never would.
Are there cases where back-to-back interrupts could cause user code to
break in really bad ways? I'm wondering whether you might have a case where
you, say, are interrupted when issuing a SQL query and then use a finally block
to do some kind of rollback and then have that rollback / cleanup step itself
itself be interrupted a little while later. If this is a scenario that's
concerning, then maybe the subsequent polls should only periodically thread
dump and not interrupt. In that case, however, we'd need to make sure that
back-to-back `killTask(interrupt=true)` calls both interrupt once on the first
time, so the logic of avoiding the creation of a second TaskReaper would need
to change a bit so that we issue a one-time interrupt in the case where we
decide that the current TaskReaper subsumes the interrupt=true one that we'd
otherwise create.
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