[SPARK-16182][CORE] Utils.scala -- terminateProcess() should call Process.destroyForcibly() if and only if Process.destroy() fails

## What changes were proposed in this pull request?

Utils.terminateProcess should `destroy()` first and only fall back to `destroyForcibly()` if it fails. It's kind of bad that we're force-killing executors -- and only in Java 8. See JIRA for an example of the impact: no shutdown

While here: `Utils.waitForProcess` should use the Java 8 method if available instead of a custom implementation.

## How was this patch tested?

Existing tests, which cover the force-kill case, and Amplab tests, which will cover both Java 7 and Java 8 eventually. However I tested locally on Java 8 and the PR builder will try Java 7 here.

Author: Sean Owen <sowen@cloudera.com>

Closes #13973 from srowen/SPARK-16182.

1 files changed, 1 insertions, 1 deletions

diff --git a/core/src/test/scala/org/apache/spark/util/UtilsSuite.scala b/core/src/test/scala/org/apache/spark/util/UtilsSuite.scala
index df279b5a37..f5d0fb00b7 100644
--- a/core/src/test/scala/org/apache/spark/util/UtilsSuite.scala
+++ b/core/src/test/scala/org/apache/spark/util/UtilsSuite.scala
@@ -863,7 +863,7 @@ class UtilsSuite extends SparkFunSuite with ResetSystemProperties with Logging {
           assert(terminated.isDefined)
           Utils.waitForProcess(process, 5000)
           val duration = System.currentTimeMillis() - start
-          assert(duration < 5000)
+          assert(duration < 6000) // add a little extra time to allow a force kill to finish
           assert(!pidExists(pid))
         } finally {
           signal(pid, "SIGKILL")