lib/fluent/plugin/out_kafka2.rb in fluent-plugin-kafka-0.6.0 vs lib/fluent/plugin/out_kafka2.rb in fluent-plugin-kafka-0.6.1

@@ -99,9 +99,19 @@
       unless formatter_conf["@type"]
         raise Fluent::ConfigError, "format/@type is required."
       end
       @formatter_proc = setup_formatter(formatter_conf)
 
+      if @default_topic.nil?
+        if @chunk_keys.include?('topic') && !@chunk_keys.include?('tag')
+          log.warn "Use 'topic' field of event record for topic but no fallback. Recommend to set default_topic or set 'tag' in buffer chunk keys like <buffer topic,tag>"
+        end
+      else
+        if @chunk_keys.include?('tag')
+          log.warn "default_topic is set. Fluentd's event tag is not used for topic"
+        end
+      end
+
       @producer_opts = {max_retries: @max_send_retries, required_acks: @required_acks}
       @producer_opts[:ack_timeout] = @ack_timeout if @ack_timeout
       @producer_opts[:compression_codec] = @compression_codec.to_sym if @compression_codec
       if @active_support_notification_regex
         require 'active_support/notifications'