Give Cluster::rr_topic "key" argument a default value

CHANGES

@@ -1,4 +1,8 @@
 
+2.5-984 | 2018-09-07 09:57:52 -0500
+
+  * Give Cluster::rr_topic "key" argument a default value (Jon Siwek, Corelight)
+
 2.5-983 | 2018-09-06 18:26:20 -0500
 
   * Disable broker message forwarding by default (Jon Siwek, Corelight)

VERSION

@@ -1 +1 @@
-2.5-983
+2.5-984

aux/broctl

@@ -1 +1 @@
-Subproject commit 9455886e959b5d9ddeccc86ae5428706e2424237
+Subproject commit 11cb3e4d33f50da4ead341a39e39efa8802d368f

scripts/base/frameworks/cluster/pools.bro

@@ -108,12 +108,16 @@ export {
 	## pool: the pool of nodes to consider.
 	##
 	## key: an arbitrary string to identify the purpose for which you're
-	##      requesting the topic.  e.g. consider using namespacing of your script
-	##      like "Intel::cluster_rr_key".
+	##      requesting the topic.  e.g. consider using a name-spaced key
+	##      like "Intel::cluster_rr_key" if you need to guarantee that
+	##      a group of messages get distributed in a well-defined pattern
+	##      without other messages being interleaved within the round-robin.
+	##      Usually sharing the default key is fine for load-balancing
+	##      purposes.
 	##
 	## Returns: a topic string associated with a cluster node that is alive,
 	##          or an empty string if nothing is alive.
-	global rr_topic: function(pool: Pool, key: string): string;
+	global rr_topic: function(pool: Pool, key: string &default=""): string;
 
 	## Distributes log message topics among logger nodes via round-robin.
 	## This will be automatically assigned to :bro:see:`Broker::log_topic`