Enabled keepalive for native protocol

Patch by brandonwilliams, reviewed by Sankalp Kohli for CASSANDRA-7380

CHANGES.txt

@@ -16,6 +16,7 @@
  * Fix infinite loop on exception while streaming (CASSANDRA-7330)
  * Reference sstables before populating key cache (CASSANDRA-7234)
 Merged from 1.2:
+ * Enable keepalive for native protocol (CASSANDRA-7380)
  * Check internal addresses for seeds (CASSANDRA-6523)
  * Fix potential / by 0 in HHOM page size calculation (CASSANDRA-7354)
  * Fix availability validation for LOCAL_ONE CL (CASSANDRA-7319)

conf/cassandra.yaml

@@ -336,7 +336,7 @@ rpc_address: localhost
 # port for Thrift to listen for clients on
 rpc_port: 9160
 
-# enable or disable keepalive on rpc connections
+# enable or disable keepalive on rpc/native connections
 rpc_keepalive: true
 
 # Cassandra provides two out-of-the-box options for the RPC Server:

src/java/org/apache/cassandra/transport/Server.java

@@ -138,6 +138,7 @@ public class Server implements CassandraDaemon.Server
         ServerBootstrap bootstrap = new ServerBootstrap(factory);
 
         bootstrap.setOption("child.tcpNoDelay", true);
+        bootstrap.setOption("child.keepAlive", DatabaseDescriptor.getRpcKeepAlive());
 
         // Set up the event pipeline factory.
         final EncryptionOptions.ClientEncryptionOptions clientEnc = DatabaseDescriptor.getClientEncryptionOptions();