[SPARK-16028][SPARKR] spark.lapply can work with active context

## What changes were proposed in this pull request?

spark.lapply and setLogLevel

## How was this patch tested?

unit test

shivaram thunterdb

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #13752 from felixcheung/rlapply.

R/pkg/R/context.R

@@ -252,17 +252,20 @@ setCheckpointDir <- function(sc, dirName) {
 #' }
 #'
 #' @rdname spark.lapply
-#' @param sc Spark Context to use
 #' @param list the list of elements
 #' @param func a function that takes one argument.
 #' @return a list of results (the exact type being determined by the function)
 #' @export
 #' @examples
 #'\dontrun{
-#' sc <- sparkR.init()
-#' doubled <- spark.lapply(sc, 1:10, function(x){2 * x})
+#' sparkR.session()
+#' doubled <- spark.lapply(1:10, function(x){2 * x})
 #'}
-spark.lapply <- function(sc, list, func) {
+spark.lapply <- function(list, func) {
+  if (!exists(".sparkRjsc", envir = .sparkREnv)) {
+    stop("SparkR has not been initialized. Please call sparkR.session()")
+  }
+  sc <- get(".sparkRjsc", envir = .sparkREnv)
   rdd <- parallelize(sc, list, length(list))
   results <- map(rdd, func)
   local <- collect(results)
@@ -274,14 +277,17 @@ spark.lapply <- function(sc, list, func) {
 #' Set new log level: "ALL", "DEBUG", "ERROR", "FATAL", "INFO", "OFF", "TRACE", "WARN"
 #'
 #' @rdname setLogLevel
-#' @param sc Spark Context to use
 #' @param level New log level
 #' @export
 #' @examples
 #'\dontrun{
-#' setLogLevel(sc, "ERROR")
+#' setLogLevel("ERROR")
 #'}
 
-setLogLevel <- function(sc, level) {
+setLogLevel <- function(level) {
+  if (!exists(".sparkRjsc", envir = .sparkREnv)) {
+    stop("SparkR has not been initialized. Please call sparkR.session()")
+  }
+  sc <- get(".sparkRjsc", envir = .sparkREnv)
   callJMethod(sc, "setLogLevel", level)
 }

R/pkg/inst/tests/testthat/test_context.R

@@ -107,8 +107,8 @@ test_that("job group functions can be called", {
 })
 
 test_that("utility function can be called", {
-  sc <- sparkR.sparkContext()
-  setLogLevel(sc, "ERROR")
+  sparkR.sparkContext()
+  setLogLevel("ERROR")
   sparkR.session.stop()
 })
 
@@ -161,7 +161,7 @@ test_that("sparkJars sparkPackages as comma-separated strings", {
 
 test_that("spark.lapply should perform simple transforms", {
   sc <- sparkR.sparkContext()
-  doubled <- spark.lapply(sc, 1:10, function(x) { 2 * x })
+  doubled <- spark.lapply(1:10, function(x) { 2 * x })
   expect_equal(doubled, as.list(2 * 1:10))
   sparkR.session.stop()
 })