[SPARK-18810][SPARKR] SparkR install.spark does not work for RCs, snapshots

## What changes were proposed in this pull request?

Support overriding the download url (include version directory) in an environment variable, `SPARKR_RELEASE_DOWNLOAD_URL`

## How was this patch tested?

unit test, manually testing
- snapshot build url
  - download when spark jar not cached
  - when spark jar is cached
- RC build url
  - download when spark jar not cached
  - when spark jar is cached
- multiple cached spark versions
- starting with sparkR shell

To use this,
```
SPARKR_RELEASE_DOWNLOAD_URL=http://this_is_the_url_to_spark_release_tgz R
```
then in R,
```
library(SparkR) # or specify lib.loc
sparkR.session()
```

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #16248 from felixcheung/rinstallurl.

R/pkg/R/install.R

@@ -79,19 +79,28 @@ install.spark <- function(hadoopVersion = "2.7", mirrorUrl = NULL,
     dir.create(localDir, recursive = TRUE)
   }
 
-  packageLocalDir <- file.path(localDir, packageName)
-
   if (overwrite) {
     message(paste0("Overwrite = TRUE: download and overwrite the tar file",
                    "and Spark package directory if they exist."))
   }
 
+  releaseUrl <- Sys.getenv("SPARKR_RELEASE_DOWNLOAD_URL")
+  if (releaseUrl != "") {
+    packageName <- basenameSansExtFromUrl(releaseUrl)
+  }
+
+  packageLocalDir <- file.path(localDir, packageName)
+
   # can use dir.exists(packageLocalDir) under R 3.2.0 or later
   if (!is.na(file.info(packageLocalDir)$isdir) && !overwrite) {
-    fmt <- "%s for Hadoop %s found, with SPARK_HOME set to %s"
-    msg <- sprintf(fmt, version, ifelse(hadoopVersion == "without", "Free build", hadoopVersion),
-                   packageLocalDir)
-    message(msg)
+    if (releaseUrl != "") {
+      message(paste(packageName, "found, setting SPARK_HOME to", packageLocalDir))
+    } else {
+      fmt <- "%s for Hadoop %s found, setting SPARK_HOME to %s"
+      msg <- sprintf(fmt, version, ifelse(hadoopVersion == "without", "Free build", hadoopVersion),
+                     packageLocalDir)
+      message(msg)
+    }
     Sys.setenv(SPARK_HOME = packageLocalDir)
     return(invisible(packageLocalDir))
   } else {
@@ -104,7 +113,12 @@ install.spark <- function(hadoopVersion = "2.7", mirrorUrl = NULL,
   if (tarExists && !overwrite) {
     message("tar file found.")
   } else {
-    robustDownloadTar(mirrorUrl, version, hadoopVersion, packageName, packageLocalPath)
+    if (releaseUrl != "") {
+      message("Downloading from alternate URL:\n- ", releaseUrl)
+      downloadUrl(releaseUrl, packageLocalPath, paste0("Fetch failed from ", releaseUrl))
+    } else {
+      robustDownloadTar(mirrorUrl, version, hadoopVersion, packageName, packageLocalPath)
+    }
   }
 
   message(sprintf("Installing to %s", localDir))
@@ -182,16 +196,18 @@ getPreferredMirror <- function(version, packageName) {
 }
 
 directDownloadTar <- function(mirrorUrl, version, hadoopVersion, packageName, packageLocalPath) {
-  packageRemotePath <- paste0(
-    file.path(mirrorUrl, version, packageName), ".tgz")
+  packageRemotePath <- paste0(file.path(mirrorUrl, version, packageName), ".tgz")
   fmt <- "Downloading %s for Hadoop %s from:\n- %s"
   msg <- sprintf(fmt, version, ifelse(hadoopVersion == "without", "Free build", hadoopVersion),
                  packageRemotePath)
   message(msg)
+  downloadUrl(packageRemotePath, packageLocalPath, paste0("Fetch failed from ", mirrorUrl))
+}
 
-  isFail <- tryCatch(download.file(packageRemotePath, packageLocalPath),
+downloadUrl <- function(remotePath, localPath, errorMessage) {
+  isFail <- tryCatch(download.file(remotePath, localPath),
                      error = function(e) {
-                       message(sprintf("Fetch failed from %s", mirrorUrl))
+                       message(errorMessage)
                        print(e)
                        TRUE
                      })

R/pkg/R/utils.R

@@ -841,7 +841,7 @@ captureJVMException <- function(e, method) {
 #
 # @param inputData a list of rows, with each row a list
 # @return data.frame with raw columns as lists
-rbindRaws <- function(inputData){
+rbindRaws <- function(inputData) {
   row1 <- inputData[[1]]
   rawcolumns <- ("raw" == sapply(row1, class))
 
@@ -851,3 +851,15 @@ rbindRaws <- function(inputData){
   out[!rawcolumns] <- lapply(out[!rawcolumns], unlist)
   out
 }
+
+# Get basename without extension from URL
+basenameSansExtFromUrl <- function(url) {
+  # split by '/'
+  splits <- unlist(strsplit(url, "^.+/"))
+  last <- tail(splits, 1)
+  # this is from file_path_sans_ext
+  # first, remove any compression extension
+  filename <- sub("[.](gz|bz2|xz)$", "", last)
+  # then, strip extension by the last '.'
+  sub("([^.]+)\\.[[:alnum:]]+$", "\\1", filename)
+}

R/pkg/inst/tests/testthat/test_utils.R

@@ -228,4 +228,15 @@ test_that("varargsToStrEnv", {
   expect_warning(varargsToStrEnv(1, 2, 3, 4), "Unnamed arguments ignored: 1, 2, 3, 4.")
 })
 
+test_that("basenameSansExtFromUrl", {
+  x <- paste0("http://people.apache.org/~pwendell/spark-nightly/spark-branch-2.1-bin/spark-2.1.1-",
+              "SNAPSHOT-2016_12_09_11_08-eb2d9bf-bin/spark-2.1.1-SNAPSHOT-bin-hadoop2.7.tgz")
+  y <- paste0("http://people.apache.org/~pwendell/spark-releases/spark-2.1.0-rc2-bin/spark-2.1.0-",
+              "bin-hadoop2.4-without-hive.tgz")
+  expect_equal(basenameSansExtFromUrl(x), "spark-2.1.1-SNAPSHOT-bin-hadoop2.7")
+  expect_equal(basenameSansExtFromUrl(y), "spark-2.1.0-bin-hadoop2.4-without-hive")
+  z <- "http://people.apache.org/~pwendell/spark-releases/spark-2.1.0--hive.tar.gz"
+  expect_equal(basenameSansExtFromUrl(z), "spark-2.1.0--hive")
+})
+
 sparkR.session.stop()