[SPARK-8528] Expose SparkContext.applicationId in PySpark

Use case - we want to log applicationId (YARN in hour case) to request help with troubleshooting from the DevOps

Author: Vladimir Vladimirov <vladimir.vladimirov@magnetic.com>

Closes #6936 from smartkiwi/master and squashes the following commits:

870338b [Vladimir Vladimirov] this would make doctest to run in python3
0eae619 [Vladimir Vladimirov] Scala doesn't use u'...' for unicode literals
14d77a8 [Vladimir Vladimirov] stop using ELLIPSIS
b4ebfc5 [Vladimir Vladimirov] addressed PR feedback - updated docstring
223a32f [Vladimir Vladimirov] fixed test - applicationId is property that returns the string
3221f5a [Vladimir Vladimirov] [SPARK-8528] added documentation for Scala
2cff090 [Vladimir Vladimirov] [SPARK-8528] add applicationId property for SparkContext object in pyspark

core/src/main/scala/org/apache/spark/SparkContext.scala

@@ -315,6 +315,14 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
     _dagScheduler = ds
   }
 
+  /**
+   * A unique identifier for the Spark application.
+   * Its format depends on the scheduler implementation.
+   * (i.e.
+   *  in case of local spark app something like 'local-1433865536131'
+   *  in case of YARN something like 'application_1433865536131_34483'
+   * )
+   */
   def applicationId: String = _applicationId
   def applicationAttemptId: Option[String] = _applicationAttemptId
 

python/pyspark/context.py

@@ -291,6 +291,21 @@ class SparkContext(object):
         """
         return self._jsc.version()
 
+    @property
+    @ignore_unicode_prefix
+    def applicationId(self):
+        """
+        A unique identifier for the Spark application.
+        Its format depends on the scheduler implementation.
+        (i.e.
+            in case of local spark app something like 'local-1433865536131'
+            in case of YARN something like 'application_1433865536131_34483'
+        )
+        >>> sc.applicationId  # doctest: +ELLIPSIS
+        u'local-...'
+        """
+        return self._jsc.sc().applicationId()
+
     @property
     def startTime(self):
         """Return the epoch time when the Spark Context was started."""