konlue opened a new pull request, #7938:
URL: https://github.com/apache/shenyu/pull/7938
Fixes #7919.
## Summary
An inbound QoS 2 `PUBLISH` was always fanned out to subscribers and only
answered with `PUBREC` — no receiving-side state was kept. A client
retransmitting the same packet id before its `PUBREL` (e.g. after a slow
`PUBREC`) therefore got the message delivered to subscribers a second time
under a freshly allocated packet id, breaking exactly-once.
## Modifications
- New `InflightRepository` (`BaseRepository`, so `MqttBootstrapServer`
registers it with the other repositories): per-client set of inbound packet ids
currently in the acknowledgement flow.
- `Publish` now registers the packet id before delivery; only a first-seen
packet id is fanned out, and every QoS 2 publish (first or retransmitted) is
answered with `PUBREC`. QoS 0/1 paths are unchanged, and an unknown client (no
CONNECT handshake seen) keeps the previous behavior.
- `PubRel` releases the packet id when `PUBCOMP` is sent, so the id becomes
reusable; a `PUBREL` for an unknown packet id still gets `PUBCOMP`, per spec.
- `Disconnect.cleanChannel` discards the in-flight state together with the
session on a clean-session disconnect; a persistent session keeps it across
reconnects, matching the session-present resumption semantics.
## Verifying this change
- [x] `testQos2RetransmitIsPublishedExactlyOnce`: packet id 77 delivered
once; the DUP retransmission is answered with `PUBREC` and the subscriber still
sees exactly one publication. Fails on the previous code (two deliveries).
- [x] `testPubRelReleasesInflightForRedelivery`: `PUBREL` → `PUBCOMP`, and
the same packet id may be delivered again afterwards.
- [x] `testPubRelForUnknownPacketIdStillRespondsWithPubComp`.
- [x] Full module tests and Checkstyle pass:
```bash
./mvnw -pl shenyu-protocol/shenyu-protocol-mqtt checkstyle:check
```
132/132 green, checkstyle clean.
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