KIP-637 — Include min.insync.replicas in MetadataResponse to make Producer smarter in partitioning events

Discussion ProducerProtocol

Proposes including `min.insync.replicas` per-partition in the `MetadataResponse` so that producers can proactively avoid routing to partitions that cannot satisfy the configured `acks=all` requirement. With `acks=all`, a partition with fewer ISRs than `min.insync.replicas` will reject produce requests; the producer currently has no way to detect this without attempting the write and receiving a `NOT_ENOUGH_REPLICAS` error.

Protocol Impact

Metadata

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