Claude
5db56e70a0
Six consumers on two partitions under a consumer group, a share group with the default share.acquire.mode and a share group with record_limit; the three acknowledgement types and a record that is released until Kafka stops redelivering it; a new share group starting at latest; the ordering a share group gives up; and Spring Kafka's share containers in implicit and manual acknowledgement modes. Tests run against a real broker (scripts/broker-up.sh) and write output/. Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01Lm655hdgDo5xsSLNomgdsy
60 lines
3.2 KiB
Markdown
60 lines
3.2 KiB
Markdown
# share-groups
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Companion code for *Queues for Kafka: Share Groups with Spring for Apache Kafka 4* on
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[ankurm.com](https://ankurm.com/kafka-share-groups-spring-kafka-4-queues-for-kafka/).
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What a Kafka **share group** (KIP-932) does differently from a consumer group, measured against a
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real broker: how many consumers can share one partition, what the three acknowledgement types do to a
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record, why a new share group sees nothing, and what ordering you give up. The same ideas are then run
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through Spring Kafka's share containers.
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## Versions
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| Artifact | Version |
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| Spring Boot | 4.1.1 (GA; `4.2.0-M2` is a milestone) |
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| Spring Kafka | 4.1.1, managed by the Boot BOM (share consumer support is already in this GA release) |
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| kafka-clients | 4.2.1, managed by the Boot BOM |
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| Kafka broker | 4.3.1, started by `scripts/broker-up.sh` (`share.version` is finalized at level 1 by default; no feature flag was set) |
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| JDK | 25 (LTS) |
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## Quickstart
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```
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scripts/broker-up.sh # downloads Kafka 4.3.1 (checksum-verified), starts KRaft on localhost:9092
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scripts/run-all.sh # runs every test and rewrites output/*.txt
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scripts/broker-down.sh
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```
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The tests do not start a broker themselves. Use `-Dbroker=host:port` if yours is elsewhere. Each test
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creates its own uniquely named topic and group, so reruns never see earlier records.
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## What each test is
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| Test | Role |
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| `WorkSpreadTest` | 6 consumers, a 2-partition topic, 60 records at 50 ms each: consumer group, share group with the default `share.acquire.mode`, and share group with `record_limit` |
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| `AckTypesTest` | ACCEPT, RELEASE and REJECT through the raw `KafkaShareConsumer`, including a record that is released every time |
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| `OffsetResetTest` | A new share group starts at the latest offset; `share.auto.offset.reset=earliest` is a group config set through the Admin API |
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| `OrderingTest` | One key, one partition, three consumers of different speed: arrival order is not produce order |
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| `SpringShareListenerTest` | `ShareKafkaListenerContainerFactory` in implicit and manual acknowledgement modes with `@KafkaListener` |
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`ShareConfig` is the hand-written configuration: Spring Boot 4.1.1 has no auto-configuration for share
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consumers.
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## Captured output (`output/`)
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| File | What it captures |
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| `01-work-spread.txt` | Which of six consumers received records under each of the three setups, with indicative timings |
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| `02-ack-types.txt` | Every delivery of four records: accepted, released once, rejected, released until Kafka stops redelivering |
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| `03-share-group-starts-at-latest.txt` | 3 records produced first: 0 received by default, 3 received after switching the group to earliest |
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| `04-no-ordering-guarantee.txt` | The order 40 same-key records were processed in, and the number of out-of-order neighbours |
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| `05-spring-share-listeners.txt` | Listener threads under implicit mode, and per-record release, reject and acknowledge under manual mode |
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Timings and the exact split of records between consumers differ from run to run. The shape of each
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result is stable; the milliseconds are not.
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No `docs/` chapter directory in this repository -- the intermediate and reference-depth material is in
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accordion sections inside the WordPress post.
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