Set cross_node_timeout to true by default.

Patch by Ekaterina Dimitrova, reviewed by brandonwilliams for
CASSANDRA-15216

CHANGES.txt

@@ -14,6 +14,10 @@
  * Add documentation for Java 11 support in Cassandra (CASSANDRA-15428)
  * Integrate SJK into nodetool (CASSANDRA-12197)
  * Ensure that empty clusterings with kind==CLUSTERING are Clustering.EMPTY (CASSANDRA-15498)
+ * The flag 'cross_node_timeout' has been set as true by default. This change
+   is done under the assumption that users have setup NTP on their clusters or
+   otherwise synchronize their clocks, and that clocks are mostly in sync, since
+   this is a requirement for general correctness of last write wins. (CASSANDRA-15216)
 Merged from 3.11:
  * Fix nodetool compactionstats showing extra pending task for TWCS - patch implemented (CASSANDRA-15409)
  * Fix SELECT JSON formatting for the "duration" type (CASSANDRA-15075)

NEWS.txt

@@ -218,6 +218,12 @@ Upgrading
       have been set as false by default. Operators should modify them to allow the
       creation of new views and SASI indexes, the existing ones will continue working.
       See CASSANDRA-14866 for details.
+    - CASSANDRA-15216 - The flag 'cross_node_timeout' has been set as true by default.
+      This change is done under the assumption that users have setup NTP on
+      their clusters or otherwise synchronize their clocks, and that clocks are
+      mostly in sync, since this is a requirement for general correctness of
+      last write wins.
+
 
 Materialized Views
 -------------------

conf/cassandra.yaml

@@ -923,9 +923,9 @@ slow_query_log_timeout_in_ms: 500
 # under overload conditions we will waste that much extra time processing 
 # already-timed-out requests.
 #
-# Warning: before enabling this property make sure to ntp is installed
-# and the times are synchronized between the nodes.
-cross_node_timeout: false
+# Warning: It is generally assumed that users have setup NTP on their clusters, and that clocks are modestly in sync, 
+# since this is a requirement for general correctness of last write wins.
+#cross_node_timeout: true
 
 # Set keep-alive period for streaming
 # This node will send a keep-alive message periodically with this period.

src/java/org/apache/cassandra/config/Config.java

@@ -108,7 +108,7 @@ public class Config
     public Integer streaming_connections_per_host = 1;
     public Integer streaming_keep_alive_period_in_secs = 300; //5 minutes
 
-    public boolean cross_node_timeout = false;
+    public boolean cross_node_timeout = true;
 
     public volatile long slow_query_log_timeout_in_ms = 500L;