* Use only the payload size as internode bytes.

* Cache the payload size where possible.

src/java/org/apache/cassandra/db/CounterMutationCallback.java

@@ -74,7 +74,7 @@ private static void addSensorsToResponse(Message.Builder<NoPayload> response, Mu
         // Add internode bytes sensors to the response after updating each per-table sensor with the current response
         // message size: this is missing the sensor values, but it's a good enough approximation
         Collection<Sensor> requestSensors = RequestTracker.instance.get().getSensors(Type.INTERNODE_BYTES);
-        int perSensorSize = response.currentSize(MessagingService.current_version) / tables;
+        int perSensorSize = response.currentPayloadSize(MessagingService.current_version) / tables;
         requestSensors.forEach(sensor -> RequestTracker.instance.get().incrementSensor(sensor.getContext(), sensor.getType(), perSensorSize));
         RequestTracker.instance.get().syncAllSensors();
         Function<String, String> requestParam = SensorsCustomParams::encodeTableInInternodeBytesRequestParam;

src/java/org/apache/cassandra/db/MutationVerbHandler.java

@@ -74,7 +74,7 @@ private void addSensorsToResponse(Message.Builder<NoPayload> response, Mutation
 
         // Add internode bytes sensors to the response after updating each per-table sensor with the current response
         // message size: this is missing the sensor values, but it's a good enough approximation
-        int perSensorSize = response.currentSize(MessagingService.current_version) / tables;
+        int perSensorSize = response.currentPayloadSize(MessagingService.current_version) / tables;
         requestSensors = RequestTracker.instance.get().getSensors(Type.INTERNODE_BYTES);
         requestSensors.forEach(sensor -> RequestTracker.instance.get().incrementSensor(sensor.getContext(), sensor.getType(), perSensorSize));
         RequestTracker.instance.get().syncAllSensors();

src/java/org/apache/cassandra/db/ReadCommandVerbHandler.java

@@ -93,7 +93,7 @@ public void doVerb(Message<ReadCommand> message)
         }
 
         Message.Builder<ReadResponse> reply = message.responseWithBuilder(response);
-        int size = reply.currentSize(MessagingService.current_version);
+        int size = reply.currentPayloadSize(MessagingService.current_version);
         RequestTracker.instance.get().incrementSensor(context, Type.INTERNODE_BYTES, size);
         RequestTracker.instance.get().syncAllSensors();
 

src/java/org/apache/cassandra/net/Message.java

@@ -497,6 +497,8 @@ public static class Builder<T>
 
         private boolean hasId;
 
+        private Message cachedMessage;
+
         private Builder()
         {
         }
@@ -607,10 +609,12 @@ public Message<T> build()
             return doBuild(hasId ? id : nextId());
         }
 
-        public int currentSize(int version)
+        public int currentPayloadSize(int version)
         {
             // use dummy id just for the sake of computing the serialized size
-            return doBuild(0).serializedSize(version);
+            Message<T> tmp = doBuild(0);
+            cachedMessage = tmp;
+            return tmp.payloadSize(version);
         }
 
         private Message<T> doBuild(long id)
@@ -622,7 +626,11 @@ private Message<T> doBuild(long id)
             if (payload == null)
                 throw new IllegalArgumentException();
 
-            return new Message<>(new Header(id, verb, from, createdAtNanos, expiresAtNanos, flags, params), payload);
+            Message<T> tmp = new Message<>(new Header(id, verb, from, createdAtNanos, expiresAtNanos, flags, params), payload);
+            if (cachedMessage != null)
+                tmp.maybeCachePayloadSize(cachedMessage);
+
+            return tmp;
         }
     }
 
@@ -1473,7 +1481,7 @@ public int serializedSize(int version)
     private int payloadSizeSG10 = -1;
     private int payloadSizeDSE68 = -1;
 
-    private int payloadSize(int version)
+    protected int payloadSize(int version)
     {
         switch (version)
         {
@@ -1506,6 +1514,25 @@ private int payloadSize(int version)
         }
     }
 
+    protected void maybeCachePayloadSize(Message other)
+    {
+        if (payload == other.payload)
+        {
+            if (other.payloadSize30 > 0)
+                payloadSize30 = other.payloadSize30;
+            if (other.payloadSize3014 > 0)
+                payloadSize3014 = other.payloadSize3014;
+            if (other.payloadSize40 > 0)
+                payloadSize40 = other.payloadSize40;
+            if (other.payloadSize41 > 0)
+                payloadSize41 = other.payloadSize41;
+            if (other.payloadSizeSG10 > 0)
+                payloadSizeSG10 = other.payloadSizeSG10;
+            if (other.payloadSizeDSE68 > 0)
+                payloadSizeDSE68 = other.payloadSizeDSE68;
+        }
+    }
+
     static class OversizedMessageException extends RuntimeException
     {
         OversizedMessageException(int size)

test/unit/org/apache/cassandra/db/CounterMutationCallbackTest.java

@@ -128,7 +128,7 @@ public void testCounterMutationCallback()
                .withFlag(MessageFlag.CALL_BACK_ON_FAILURE)
                .withParam(TRACE_SESSION, UUID.randomUUID())
                .build();
-        int responseSize = msg.emptyResponseBuilder().currentSize(MessagingService.current_version);
+        int responseSize = msg.emptyResponseBuilder().currentPayloadSize(MessagingService.current_version);
 
         RequestSensors requestSensors = new RequestSensors();
         RequestTracker.instance.set(requestSensors);