ijuma commented on code in PR #18845:
URL: https://github.com/apache/kafka/pull/18845#discussion_r1952871969


##########
metadata/src/main/java/org/apache/kafka/image/FeaturesDelta.java:
##########
@@ -58,7 +59,14 @@ public void finishSnapshot() {
 
     public void replay(FeatureLevelRecord record) {
         if (record.name().equals(MetadataVersion.FEATURE_NAME)) {
-            metadataVersionChange = 
MetadataVersion.fromFeatureLevel(record.featureLevel());
+            // Support for the `metadata.version` feature flag was added in 
IBP_3_3_IV0, so it's possible (but unlikely) that we read
+            // records with a feature level that is no longer supported for 
clusters that used a pre-release version of 3.3.0.
+            // We automatically fallback to IBP_3_3_IV3 in that case. We use 
explicit versions instead of `MINIMUM_VERSION` because
+            // we want to force an explicit decision if we change 
`MetadataVersion.MINIMUM_VERSION` in the future.
+            if (record.featureLevel() >= MINIMUM_PERSISTED_FEATURE_LEVEL && 
record.featureLevel() <= MetadataVersion.IBP_3_3_IV3.featureLevel())
+                metadataVersionChange = MetadataVersion.IBP_3_3_IV3;

Review Comment:
   @junrao @cmccabe Thoughts on this fallback? It seems like quite a rare edge 
case (since it requires usage of a pre-release version and for the older 
metadata version not to be compacted away if I understand correctly), but it 
seems fair to never fail while reading the log and the fallback code is pretty 
simple.



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