junrao commented on a change in pull request #9001:
URL: https://github.com/apache/kafka/pull/9001#discussion_r498420758
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File path:
clients/src/main/java/org/apache/kafka/common/feature/SupportedVersionRange.java
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@@ -17,9 +17,16 @@
package org.apache.kafka.common.feature;
import java.util.Map;
+import java.util.Objects;
+import org.apache.kafka.common.utils.Utils;
/**
- * An extended {@link BaseVersionRange} representing the min/max versions for
supported features.
+ * An extended {@link BaseVersionRange} representing the min, max and first
active versions for a
+ * supported feature:
+ * - minVersion: This is the minimum supported version for the feature.
+ * - maxVersion: This the maximum supported version for the feature.
+ * - firstActiveVersion: This is the first active version for the feature.
Versions in the range
Review comment:
Thinking about this a bit more. It seems that the intention of
firstActiveVersion is to avoid deploying a wrong version of the broker that
causes the deprecation of a finalized feature version unexpectedly. However,
the same mistake can happen with firstActiveVersion since the deprecation of a
finalized feature version is based on firstActiveVersion. So, I am not sure if
firstActiveVersion addresses a real problem.
In general, we tend to deprecate a version very slowly in AK. So, if the
mistake is to deploy a new release that actually deprecates a supported
version. Old clients are likely all gone. So, moving finalized min version to
supported min version may not cause a big problem. We can just document that
people should make sure old versions are no longer used before deploying new
releases.
If the mistake is to deploy an old version of the broker whose
maxSupportedVersion is < maxFinalizedVersion, we will fail the broker. So, this
mistake can be prevented.
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