Allow configuration to be printed in logs for diagnosis.

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

@@ -116,6 +116,10 @@ class SparkContext(
     throw new SparkException("An application must be set in your configuration")
   }
 
+  if (conf.get("spark.log-conf", "false").toBoolean) {
+    logInfo("Spark configuration:\n" + conf.toDebugString)
+  }
+
   // Set Spark driver host and port system properties
   conf.setIfMissing("spark.driver.host", Utils.localHostName())
   conf.setIfMissing("spark.driver.port", "0")

docs/configuration.md

@@ -403,6 +403,13 @@ Apart from these, the following properties are also available, and may be useful
     How many times slower a task is than the median to be considered for speculation.
   </td>
 </tr>
+<tr>
+  <td>spark.log-conf</td>
+  <td>false</td>
+  <td>
+    Log the supplied SparkConf as INFO at start of spark context.
+  </td>
+</tr>
 </table>
 
 ## Viewing Spark Properties