kaas (broker binary)

The broker entrypoint: dispatcher registration, env wiring, the cluster runtime, and the graceful SIGTERM drain.

bins/kaas is deliberately thin on logic and thick on wiring — it's where every seam the library crates expose gets a production implementation plugged in.

main.rs: parses KAAS_LISTENERS (default: one plain listener on 0.0.0.0:9092), selects storage (KAAS_DATA_DIR set → disk engine; unset → in-memory dev mode), builds the per-listener auth engines and the cluster-wide authorizer/quota checker, registers every handler with the dispatcher, spawns the kube topic watch (in cluster mode), starts /healthz//readyz, and owns the graceful SIGTERM drain — relinquish every open partition (persisting manifests + producer snapshots, closing FDs), then flush remaining manifests as defence-in-depth (file-handle ownership). It also carries the --init init-container entry point, the retention-cleaner tick, the credentials/ACL hot-reload task, and the JWKS refresher loops for OAuth listeners.

cluster.rs: the cluster runtime — Lease election glue, heartbeat client/server wiring, broker-set watcher (2 s alive-set poll), topic-change notifier, the assignment loop when this broker is controller, the fence/marker watchers, the txn timeout reaper + gh #225 marker reconcile (same 10 s tick), and the assignment-source hot-swap (the boot-time always-true stub replaced by the real Coordinator-backed source once the runtime is up — the gh #92 dance described in Consumer-group coordination).

Mode selection is three-way (see the top comment in bins/kaas/src/cluster.rs): neither var set → in-memory dev mode (no cluster runtime, local-lease "I lead everything"); KAAS_DATA_DIR set but MY_POD_NAME unset → single-broker disk mode (a Coordinator + assignment loop is installed); MY_POD_NAME set → cluster mode.

Integration tests live in bins/kaas/tests/ — smoke.rs, auth_smoke.rs, byte_opacity.rs, cluster_bringup.rs, cluster_smoke.rs, eos_v2.rs, oauth_smoke.rs, retention.rs — the suites the verification story leans on.

Start reading at main.rs top to bottom — it reads as a map of the whole system.