feat(kafka_producer): add validation for empty message key when strategy = key_dispatch

Fixes https://emqx.atlassian.net/browse/EMQX-9979

apps/emqx_bridge_kafka/src/emqx_bridge_kafka.app.src

@@ -1,6 +1,6 @@
 {application, emqx_bridge_kafka, [
     {description, "EMQX Enterprise Kafka Bridge"},
-    {vsn, "0.1.2"},
+    {vsn, "0.1.3"},
     {registered, [emqx_bridge_kafka_consumer_sup]},
     {applications, [
         kernel,

apps/emqx_bridge_kafka/src/emqx_bridge_kafka.erl

@@ -247,7 +247,8 @@ fields(producer_opts) ->
         {kafka,
             mk(ref(producer_kafka_opts), #{
                 required => true,
-                desc => ?DESC(producer_kafka_opts)
+                desc => ?DESC(producer_kafka_opts),
+                validator => fun producer_strategy_key_validator/1
             })}
     ];
 fields(producer_kafka_opts) ->
@@ -459,3 +460,11 @@ consumer_topic_mapping_validator(TopicMapping = [_ | _]) ->
         false ->
             {error, "Kafka topics must not be repeated in a bridge"}
     end.
+
+producer_strategy_key_validator(#{
+    <<"partition_strategy">> := key_dispatch,
+    <<"message">> := #{<<"key">> := ""}
+}) ->
+    {error, "Message key cannot be empty when `key_dispatch` strategy is used"};
+producer_strategy_key_validator(_) ->
+    ok.

apps/emqx_bridge_kafka/test/emqx_bridge_kafka_tests.erl

@@ -138,6 +138,36 @@ kafka_consumer_test() ->
 
     ok.
 
+message_key_dispatch_validations_test() ->
+    Conf0 = kafka_producer_new_hocon(),
+    Conf1 =
+        Conf0 ++
+            "\n"
+            "bridges.kafka.myproducer.kafka.message.key = \"\""
+            "\n"
+            "bridges.kafka.myproducer.kafka.partition_strategy = \"key_dispatch\"",
+    Conf = parse(Conf1),
+    ?assertMatch(
+        #{
+            <<"kafka">> :=
+                #{
+                    <<"partition_strategy">> := <<"key_dispatch">>,
+                    <<"message">> := #{<<"key">> := <<>>}
+                }
+        },
+        emqx_utils_maps:deep_get([<<"bridges">>, <<"kafka">>, <<"myproducer">>], Conf)
+    ),
+    ?assertThrow(
+        {_, [
+            #{
+                path := "bridges.kafka.myproducer.kafka",
+                reason := "Message key cannot be empty when `key_dispatch` strategy is used"
+            }
+        ]},
+        check(Conf)
+    ),
+    ok.
+
 %%===========================================================================
 %% Helper functions
 %%===========================================================================

changes/ee/feat-10841.en.md

@@ -0,0 +1 @@
+Added a schema validation to ensure message key is not empty when dispatching by key in Kafka Producer bridge.