[GitHub] [kafka] chia7712 commented on a change in pull request #9435: KAFKA-10606: Disable auto topic creation for fetch-all-topic-metadata request

[GitBox <gi...@apache.org>]

chia7712 commented on a change in pull request #9435:
URL: https://github.com/apache/kafka/pull/9435#discussion_r534752326



##########
File path: core/src/main/scala/kafka/server/KafkaApis.scala
##########
@@ -1243,19 +1244,30 @@ class KafkaApis(val requestChannel: RequestChannel,
       topicResponses
     } else {
       val nonExistentTopics = topics.diff(topicResponses.map(_.name).toSet)
-      val responsesForNonExistentTopics = nonExistentTopics.map { topic =>
+      val responsesForNonExistentTopics = nonExistentTopics.flatMap { topic =>
         if (isInternal(topic)) {
           val topicMetadata = createInternalTopic(topic)
-          if (topicMetadata.errorCode == Errors.COORDINATOR_NOT_AVAILABLE.code)
-            metadataResponseTopic(Errors.INVALID_REPLICATION_FACTOR, topic, true, util.Collections.emptyList())
-          else
-            topicMetadata
+          List(
+            if (topicMetadata.errorCode == Errors.COORDINATOR_NOT_AVAILABLE.code)
+              metadataResponseTopic(Errors.INVALID_REPLICATION_FACTOR, topic, true, util.Collections.emptyList())
+            else
+              topicMetadata
+          )
+        } else if (isFetchAllMetadata) {
+          // KAFKA-10606: If this request is to get metadata for all topics, auto topic creation should not be allowed
+          // The special handling is necessary on broker side because allowAutoTopicCreation is hard coded to true
+          // for backward compatibility on client side.
+          //
+          // However, in previous versions, UNKNOWN_TOPIC_OR_PARTITION won't happen on fetch all metadata,
+          // so, for backward-compatibility, we need to skip these not founds during fetch all metadata here.
+          Nil

Review comment:
       Is ```Some/None``` more readable than ```List/Nil```?




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