feat: add default handler for pubsub ping command (apache#7058)

Author: bzp2010

apisix/core/pubsub.lua

@@ -123,6 +123,11 @@ function _M.new()
         cmd_handler = {},
     }, mt)
 
+    -- add default ping handler
+    obj:on("cmd_ping", function (params)
+        return { pong_resp = params }
+    end)
+
     return obj
 end
 

apisix/include/apisix/model/pubsub.proto

@@ -73,8 +73,8 @@ message CmdKafkaFetch {
 message PubSubReq {
     int64 sequence = 1;
     oneof req {
-        CmdEmpty cmd_empty                       = 31;
-        CmdPing cmd_ping                         = 32;
+        CmdEmpty           cmd_empty             = 31;
+        CmdPing            cmd_ping              = 32;
         CmdKafkaFetch      cmd_kafka_fetch       = 33;
         CmdKafkaListOffset cmd_kafka_list_offset = 34;
     };
@@ -135,9 +135,9 @@ message KafkaListOffsetResp {
 message PubSubResp {
     int64 sequence = 1;
     oneof resp {
-        ErrorResp error_resp                       = 31;
-        PongResp pong_resp                         = 32;
-        KafkaFetchResp kafka_fetch_resp            = 33;
+        ErrorResp           error_resp             = 31;
+        PongResp            pong_resp              = 32;
+        KafkaFetchResp      kafka_fetch_resp       = 33;
         KafkaListOffsetResp kafka_list_offset_resp = 34;
     };
 }