[SPARK-5181] do not print writing WAL log when WAL is disabled

https://issues.apache.org/jira/browse/SPARK-5181

Currently, even the logManager is not created, we still see the log entry
s"Writing to log $record"

a simple fix to make log more accurate

Author: CodingCat <zhunansjtu@gmail.com>

Closes #3985 from CodingCat/SPARK-5181 and squashes the following commits:

0e27dc5 [CodingCat] do not print writing WAL log when WAL is disabled

1 files changed, 4 insertions, 2 deletions

diff --git a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceivedBlockTracker.scala b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceivedBlockTracker.scala
index 2ce458cdde..c3d9d7b681 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceivedBlockTracker.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceivedBlockTracker.scala
@@ -203,9 +203,11 @@ private[streaming] class ReceivedBlockTracker(
 
   /** Write an update to the tracker to the write ahead log */
   private def writeToLog(record: ReceivedBlockTrackerLogEvent) {
-    logDebug(s"Writing to log $record")
-    logManagerOption.foreach { logManager =>
+    if (isLogManagerEnabled) {
+      logDebug(s"Writing to log $record")
+      logManagerOption.foreach { logManager =>
         logManager.writeToLog(ByteBuffer.wrap(Utils.serialize(record)))
+      }
     }
   }