Kafka compatibility
Roxa implements the Kafka wire protocol over TCP (port 9092 by default): existing applications connect without a rewrite — only the broker address changes. Below is an honest matrix of what is supported and verified by end-to-end tests with real clients (kcat / librdkafka).
Supported and verified e2e
| Capability | Details |
|---|---|
| ApiVersions, Metadata | version negotiation, broker/topic discovery |
| Produce | RecordBatch v2, CRC32C, monotonic offsets — ordering within a partition is guaranteed |
| Fetch | reading from an arbitrary offset |
| ListOffsets | earliest / latest |
| Consumer groups | FindCoordinator, Join/Sync, Heartbeat, Leave, OffsetCommit/OffsetFetch, rebalancing |
| Idempotent producers | InitProducerId, PID + sequence, deduplication within a session |
| Compression | gzip, snappy, lz4, zstd |
| SASL/PLAIN | SaslHandshake + SaslAuthenticate; requests are rejected until authentication |
| Key-based routing | murmur2 — parity with Kafka's partition distribution |
Guarantees
- At-least-once: the producer is acknowledged only after the batch is durably written to storage (S3/MinIO or the file system). There is no gap between “accepted” and “saved” — by construction.
- Idempotence applies within a producer session (the PID does not survive a broker restart).
Not supported yet
An honest list of what is missing (if any of this blocks your scenario — write to us, it shapes our priorities):
- Transactions / exactly-once semantics.
- Log compaction (retention is by size and time).
- Kafka Connect, Schema Registry.
- ACLs at the Kafka protocol level (authentication is SASL/PLAIN; the admin/viewer roles live on gRPC).
Verified with clients
The end-to-end tests run against real kcat/librdkafka — that is, every client built on librdkafka (Python confluent-kafka, Go confluent-kafka-go, C#, PHP and others). The Java client uses the same protocol specification but is not yet exercised separately in e2e — if it runs in your production, start with a test on the demo environment or let us know.
Connection examples — on the next page.