updated spark configuration

Updated Spark configuration to output history to a directory on QFS

spark-qfs-swarm/worker-node/spark-conf/spark-defaults.conf

@@ -1,5 +1,5 @@
 # performance optimizations
-spark.serializer			org.apache.spark.serializer.KryoSerializer
+spark.serializer		org.apache.spark.serializer.KryoSerializer
 spark.default.parallelism	100
 
 # worker node / executor set up
@@ -8,12 +8,18 @@ spark.executor.memory 		24g
 spark.executor.cores		6
 
 # driver configurations
-spark.driver.memory			8g
-spark.driver.cores			2
+spark.driver.memory		8g
+spark.driver.cores		2
 
 # operational configurations
-spark.logConf				true
+spark.logConf			true
 
 # This setting is to tell the class loaders in Spark that they
 # only need to load the QFS access libraries once 
 spark.sql.hive.metastore.sharedPrefixes         com.quantcast.qfs
+
+# Set up retention of Spark events to enable the history server.
+# The configured directory needs to be created prior to launching
+# Spark master.
+spark.eventLog.enabled		true
+spark.eventLog.dir		qfs:///history/spark/