[SPARK-17964][SPARKR] Enable SparkR with Mesos client mode and cluster mode

## What changes were proposed in this pull request?

Enabled SparkR with Mesos client mode and cluster mode. Just a few changes were required to get this working on Mesos: (1) removed the SparkR on Mesos error checks and (2) do not require "--class" to be specified for R apps. The logic to check spark.mesos.executor.home was already in there.

sun-rui

## How was this patch tested?

1. SparkSubmitSuite
2. On local mesos cluster (on laptop): ran SparkR shell, spark-submit client mode, and spark-submit cluster mode, with the "examples/src/main/R/dataframe.R" example application.
3. On multi-node mesos cluster: ran SparkR shell, spark-submit client mode, and spark-submit cluster mode, with the "examples/src/main/R/dataframe.R" example application. I tested with the following --conf values set: spark.mesos.executor.docker.image and spark.mesos.executor.home

This contribution is my original work and I license the work to the project under the project's open source license.

Author: Susan X. Huynh <[email protected]>

Closes #15700 from susanxhuynh/susan-r-branch.

Author: susanxhuynh

core/src/main/scala/org/apache/spark/api/r/RUtils.scala

@@ -84,7 +84,6 @@ private[spark] object RUtils {
       }
     } else {
       // Otherwise, assume the package is local
-      // TODO: support this for Mesos
       val sparkRPkgPath = localSparkRPackagePath.getOrElse {
           throw new SparkException("SPARK_HOME not set. Can't locate SparkR package.")
       }

core/src/main/scala/org/apache/spark/deploy/SparkSubmit.scala

@@ -322,17 +322,14 @@ object SparkSubmit {
     }
 
     // Require all R files to be local
-    if (args.isR && !isYarnCluster) {
+    if (args.isR && !isYarnCluster && !isMesosCluster) {
       if (Utils.nonLocalPaths(args.primaryResource).nonEmpty) {
         printErrorAndExit(s"Only local R files are supported: ${args.primaryResource}")
       }
     }
 
     // The following modes are not supported or applicable
     (clusterManager, deployMode) match {
-      case (MESOS, CLUSTER) if args.isR =>
-        printErrorAndExit("Cluster deploy mode is currently not supported for R " +
-          "applications on Mesos clusters.")
       case (STANDALONE, CLUSTER) if args.isPython =>
         printErrorAndExit("Cluster deploy mode is currently not supported for python " +
           "applications on standalone clusters.")
@@ -410,9 +407,9 @@ object SparkSubmit {
       printErrorAndExit("Distributing R packages with standalone cluster is not supported.")
     }
 
-    // TODO: Support SparkR with mesos cluster
-    if (args.isR && clusterManager == MESOS) {
-      printErrorAndExit("SparkR is not supported for Mesos cluster.")
+    // TODO: Support distributing R packages with mesos cluster
+    if (args.isR && clusterManager == MESOS && !RUtils.rPackages.isEmpty) {
+      printErrorAndExit("Distributing R packages with mesos cluster is not supported.")
     }
 
     // If we're running an R app, set the main class to our specific R runner
@@ -598,6 +595,9 @@ object SparkSubmit {
         if (args.pyFiles != null) {
           sysProps("spark.submit.pyFiles") = args.pyFiles
         }
+      } else if (args.isR) {
+        // Second argument is main class
+        childArgs += (args.primaryResource, "")
       } else {
         childArgs += (args.primaryResource, args.mainClass)
       }