[ISSUE #100] Priority Message Proto Definition (#101)

Author: imzs

apache/rocketmq/v2/definition.proto

@@ -149,6 +149,9 @@ enum MessageType {
 
   // lite topic
   LITE = 5;
+
+  // Messages that lower prioritised ones may need to wait for higher priority messages to be processed first
+  PRIORITY = 6;
 }
 
 enum DigestType {
@@ -278,6 +281,9 @@ message SystemProperties {
 
   // lite topic
   optional string lite_topic = 21;
+
+  // Priority of message, which is optional
+  optional int32 priority = 22;
 }
 
 message DeadLetterQueue {