[SW-1755] Don't need to stop worker nodes in internal backend, spark takes care of it as it shutdowns the executors

core/src/main/scala/org/apache/spark/h2o/H2OContext.scala

@@ -311,9 +311,11 @@ abstract class H2OContext private(val sparkSession: SparkSession, private val co
       if (stopSparkContext) {
         sparkContext.stop()
       }
-      // H2O cluster is managed by the user in case of manual start of external backend.
-      if (!(conf.isManualClusterStartUsed && conf.runsInExternalClusterMode)) {
-        H2O.orderlyShutdown()
+      // Run orderly shutdown only in case of automatic mode of external backend, because:
+      // In internal backend, Spark takes care of stopping executors automatically
+      // In manual mode of external backend, the H2O cluster is managed by the user
+      if (conf.runsInExternalClusterMode && conf.isAutoClusterStartUsed) {
+        H2O.orderlyShutdown(conf.externalBackendStopTimeout)
       }
       H2OContext.instantiatedContext.set(null)
       stopped = true

core/src/main/scala/org/apache/spark/h2o/backends/external/ExternalBackendConf.scala

@@ -64,6 +64,7 @@ trait ExternalBackendConf extends SharedBackendConf {
     PROP_EXTERNAL_COMMUNICATION_BLOCK_SIZE._1,
     PROP_EXTERNAL_COMMUNICATION_BLOCK_SIZE._2)
   def externalCommunicationBlockSize: String = sparkConf.get(PROP_EXTERNAL_COMMUNICATION_BLOCK_SIZE._1, PROP_EXTERNAL_COMMUNICATION_BLOCK_SIZE._2)
+  def externalBackendStopTimeout: Int = sparkConf.getInt(PROP_EXTERNAL_BACKEND_STOP_TIMEOUT._1, PROP_EXTERNAL_BACKEND_STOP_TIMEOUT._2)
   private[backends] def isBackendVersionCheckDisabled() = sparkConf.getBoolean(PROP_EXTERNAL_DISABLE_VERSION_CHECK._1, PROP_EXTERNAL_DISABLE_VERSION_CHECK._2)
 
   /** Setters */
@@ -130,6 +131,7 @@ trait ExternalBackendConf extends SharedBackendConf {
   def setExternalH2ODriverPortRange(portRange: String): H2OConf = set(PROP_EXTERNAL_DRIVER_PORT_RANGE._1, portRange)
   def setExternalExtraMemoryPercent(memoryPercent: Int): H2OConf = set(PROP_EXTERNAL_EXTRA_MEMORY_PERCENT._1, memoryPercent.toString)
   def setExternalCommunicationBlockSize(blockSize: String): H2OConf = set(PROP_EXTERNAL_COMMUNICATION_BLOCK_SIZE._1, blockSize)
+  def setExternalBackendStopTimeout(timeout: Int): H2OConf = set(PROP_EXTERNAL_BACKEND_STOP_TIMEOUT._1, timeout.toString)
 
   def externalConfString: String =
     s"""Sparkling Water configuration:
@@ -231,6 +233,12 @@ object ExternalBackendConf {
     */
   val PROP_EXTERNAL_COMMUNICATION_BLOCK_SIZE = ("spark.ext.h2o.external.communication.blockSize", "1m")
 
+  /**
+    * Timeout for confirmation from worker nodes when stopping the external backend. It is also
+    * possible to pass -1 to ensure the indefinite timeout. The unit is milliseconds.
+    */
+  val PROP_EXTERNAL_BACKEND_STOP_TIMEOUT = ("spark.ext.h2o.external.backend.stop.timeout", 10000)
+
   /** Disable version check of external H2O backend */
   val PROP_EXTERNAL_DISABLE_VERSION_CHECK = ("spark.ext.h2o.external.disable.version.check", false)
 }

doc/src/site/sphinx/configuration/configuration_properties.rst

@@ -364,6 +364,13 @@ External backend configuration properties
 |                                                       |                | suffix "k", "m" or "g" (e.g.        |
 |                                                       |                | ``450k``, ``3m``)                   |
 +-------------------------------------------------------+----------------+-------------------------------------+
+| ``spark.ext.h2o.external.backend.stop.timeout``       | ``10000ms``    | Timeout for confirmation from       |
+|                                                       |                | worker nodes when stopping the      |
+|                                                       |                | external backend. It is also        |
+|                                                       |                | possible to pass ``-1`` to ensure   |
+|                                                       |                | the indefinite timeout. The unit is |
+|                                                       |                | milliseconds.                       |
++-------------------------------------------------------+----------------+-------------------------------------+
 
 --------------
 

py/src/ai/h2o/sparkling/H2OConf.py

@@ -464,6 +464,10 @@ def setExternalCommunicationBlockSize(self, blockSize):
         self._jconf.setExternalCommunicationBlockSize(blockSize)
         return self
 
+    def setExternalBackendStopTimeout(self, timeout):
+        self._jconf.setExternalBackendStopTimeout(timeout)
+        return self
+
     # getters independent on backend
 
     def backend_cluster_mode(self):
@@ -722,7 +726,10 @@ def externalExtraMemoryPercent(self):
 
     def externalCommunicationBlockSizeAsBytes(self):
         return self._jconf.externalCommunicationBlockSizeAsBytes()
-
+
+    def externalBackendStopTimeout(self):
+        return self._jconf.externalBackendStopTimeout()
+
     def set(self, key, value):
         self._jconf.set(key, value)
         return self

py/src/ai/h2o/sparkling/H2OContext.py

@@ -180,7 +180,7 @@ def __getClientConnectedField(self):
 
     def stop(self):
         try:
-            if not (self._conf.is_manual_cluster_start_used() and self._conf.runs_in_external_cluster_mode()):
+            if self._conf.runs_in_external_cluster_mode() and self._conf.is_auto_cluster_start_used():
                 h2o.cluster().shutdown()
         except:
             pass