[GitHub] [kafka] hachikuji commented on a change in pull request #11448: KAFKA-13417; Ensure dynamic reconfigurations set old config properly

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hachikuji commented on a change in pull request #11448:
URL: https://github.com/apache/kafka/pull/11448#discussion_r744968165



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File path: core/src/main/scala/kafka/server/DynamicBrokerConfig.scala
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@@ -516,7 +516,15 @@ class DynamicBrokerConfig(private val kafkaConfig: KafkaConfig) extends Logging
     newProps ++= staticBrokerConfigs
     overrideProps(newProps, dynamicDefaultConfigs)
     overrideProps(newProps, dynamicBrokerConfigs)
-    val oldConfig = currentConfig
+
+    // We need a copy of the current config since `currentConfig` is initialized with `kafkaConfig`
+    // which means the call to `updateCurrentConfig` would end up mutating `oldConfig`.
+    val oldConfig = if (kafkaConfig eq currentConfig) {

Review comment:
       @rajinisivaram Hmm, good point. It looks like the bug only affects KRaft since there is no call to `initialize`. The code still feels a little slippery though, so maybe there is room for some defensiveness. Let me take a look.




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