[SPARK-17178][SPARKR][SPARKSUBMIT] Allow to set sparkr shell command through --conf

## What changes were proposed in this pull request?

Allow user to set sparkr shell command through --conf spark.r.shell.command

## How was this patch tested?

Unit test is added and also verify it manually through
```
bin/sparkr --master yarn-client --conf spark.r.shell.command=/usr/local/bin/R
```

Author: Jeff Zhang <zjffdu@apache.org>

Closes #14744 from zjffdu/SPARK-17178.

2 files changed, 4 insertions, 1 deletions

diff --git a/launcher/src/main/java/org/apache/spark/launcher/SparkLauncher.java b/launcher/src/main/java/org/apache/spark/launcher/SparkLauncher.java
index 7b7a7bf57b..ea56214d23 100644
--- a/launcher/src/main/java/org/apache/spark/launcher/SparkLauncher.java
+++ b/launcher/src/main/java/org/apache/spark/launcher/SparkLauncher.java
@@ -68,6 +68,8 @@ public class SparkLauncher {
 
   static final String PYSPARK_PYTHON = "spark.pyspark.python";
 
+  static final String SPARKR_R_SHELL = "spark.r.shell.command";
+
   /** Logger name to use when launching a child process. */
   public static final String CHILD_PROCESS_LOGGER_NAME = "spark.launcher.childProcLoggerName";
 
diff --git a/launcher/src/main/java/org/apache/spark/launcher/SparkSubmitCommandBuilder.java b/launcher/src/main/java/org/apache/spark/launcher/SparkSubmitCommandBuilder.java
index f6da644e4c..29c6d82cdb 100644
--- a/launcher/src/main/java/org/apache/spark/launcher/SparkSubmitCommandBuilder.java
+++ b/launcher/src/main/java/org/apache/spark/launcher/SparkSubmitCommandBuilder.java
@@ -336,7 +336,8 @@ class SparkSubmitCommandBuilder extends AbstractCommandBuilder {
             join(File.separator, sparkHome, "R", "lib", "SparkR", "profile", "shell.R"));
 
     List<String> args = new ArrayList<>();
-    args.add(firstNonEmpty(System.getenv("SPARKR_DRIVER_R"), "R"));
+    args.add(firstNonEmpty(conf.get(SparkLauncher.SPARKR_R_SHELL),
+      System.getenv("SPARKR_DRIVER_R"), "R"));
     return args;
   }