jsancio commented on code in PR #21122:
URL: https://github.com/apache/kafka/pull/21122#discussion_r3324463238
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server-common/src/main/java/org/apache/kafka/server/common/FinalizedFeatures.java:
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@@ -19,28 +19,128 @@
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
+import java.util.Optional;
-public record FinalizedFeatures(
- MetadataVersion metadataVersion,
- Map<String, Short> finalizedFeatures,
- long finalizedFeaturesEpoch
-) {
- public static FinalizedFeatures fromKRaftVersion(MetadataVersion version) {
- return new FinalizedFeatures(version, Map.of(), -1);
- }
+/**
+ * Represents the finalized feature levels for a Kafka cluster.
+ * <p>
+ * This class can be in one of three states:
+ * <ul>
+ * <li>Unknown - the metadata version has not been committed yet, e.g.
before a quorum is
+ * formed. Used as the initial state in {@code FeaturesPublisher}. (use
{@link #unknown()})</li>
+ * <li>Metadata version only - the metadata version is known but no
additional features or
+ * epoch have been set. Used when only the metadata version needs to be
represented
+ * without a full set of finalized features. (use {@link
#fromKRaftVersion(MetadataVersion)})</li>
+ * <li>Full features - metadata version, features map, and epoch are all
known. Used after
+ * the controller has committed feature records. (use {@link
#of(MetadataVersion, Map, long)})</li>
+ * </ul>
+ */
+public final class FinalizedFeatures {
+ private static final FinalizedFeatures UNKNOWN = new
FinalizedFeatures(Optional.empty(), Map.of(), -1);
+
+ private final Optional<MetadataVersion> metadataVersion;
+ private final Map<String, Short> finalizedFeatures;
+ private final long finalizedFeaturesEpoch;
- public FinalizedFeatures(
- MetadataVersion metadataVersion,
+ private FinalizedFeatures(
+ Optional<MetadataVersion> metadataVersion,
Map<String, Short> finalizedFeatures,
long finalizedFeaturesEpoch
) {
- this.metadataVersion = Objects.requireNonNull(metadataVersion);
+ this.metadataVersion = metadataVersion;
this.finalizedFeatures = new HashMap<>(finalizedFeatures);
this.finalizedFeaturesEpoch = finalizedFeaturesEpoch;
- this.finalizedFeatures.put(MetadataVersion.FEATURE_NAME,
metadataVersion.featureLevel());
+ metadataVersion.ifPresent(mv ->
+ this.finalizedFeatures.put(MetadataVersion.FEATURE_NAME,
mv.featureLevel()));
+ }
+
+ /**
+ * Returns a sentinel value representing unknown finalized features.
+ *
+ * @return the unknown finalized features instance
+ */
+ public static FinalizedFeatures unknown() {
+ return UNKNOWN;
+ }
+
+ /**
+ * Creates a new instance from the given KRaft metadata version.
+ *
+ * @param version the metadata version
+ * @return a new FinalizedFeatures instance
+ * @throws NullPointerException if version is null
+ */
+ public static FinalizedFeatures fromKRaftVersion(MetadataVersion version) {
Review Comment:
I missed this. This should be fromMetadataVersion. We now have a KRaft
version feature (kraft.version) it will be confusing to use to see kraft
version method name but the metadata version (metadata.version) is passed.
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