[SPARK-18138][DOCS] Document that Java 7, Python 2.6, Scala 2.10, Hadoop < 2.6 are deprecated in Spark 2.1.0

## What changes were proposed in this pull request?

Document that Java 7, Python 2.6, Scala 2.10, Hadoop < 2.6 are deprecated in Spark 2.1.0. This does not actually implement any of the change in SPARK-18138, just peppers the documentation with notices about it.

## How was this patch tested?

Doc build

Author: Sean Owen <sowen@cloudera.com>

Closes #15733 from srowen/SPARK-18138.

1 files changed, 12 insertions, 0 deletions

diff --git a/core/src/main/scala/org/apache/spark/SparkContext.scala b/core/src/main/scala/org/apache/spark/SparkContext.scala
index 63478c88b0..9f0f607422 100644
--- a/core/src/main/scala/org/apache/spark/SparkContext.scala
+++ b/core/src/main/scala/org/apache/spark/SparkContext.scala
@@ -183,6 +183,8 @@ class SparkContext(config: SparkConf) extends Logging {
   // log out Spark Version in Spark driver log
   logInfo(s"Running Spark version $SPARK_VERSION")
 
+  warnDeprecatedVersions()
+
   /* ------------------------------------------------------------------------------------- *
    | Private variables. These variables keep the internal state of the context, and are    |
    | not accessible by the outside world. They're mutable since we want to initialize all  |
@@ -346,6 +348,16 @@ class SparkContext(config: SparkConf) extends Logging {
     value
   }
 
+  private def warnDeprecatedVersions(): Unit = {
+    val javaVersion = System.getProperty("java.version").split("[+.\\-]+", 3)
+    if (javaVersion.length >= 2 && javaVersion(1).toInt == 7) {
+      logWarning("Support for Java 7 is deprecated as of Spark 2.0.0")
+    }
+    if (scala.util.Properties.releaseVersion.exists(_.startsWith("2.10"))) {
+      logWarning("Support for Scala 2.10 is deprecated as of Spark 2.1.0")
+    }
+  }
+
   /** Control our logLevel. This overrides any user-defined log settings.
    * @param logLevel The desired log level as a string.
    * Valid log levels include: ALL, DEBUG, ERROR, FATAL, INFO, OFF, TRACE, WARN