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feat(raft-drive-async): add drive-async config constants + liveness-reservation helper (task 1.1)

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drive_async_liveness_reserved = max(1, min(n_peers-1, n_vcpus-1)) — single
source of truth for VTASK_LIVENESS_RESERVED (deadlock-freedom floor applied
last). New DEFAULT_CONNECT_TIMEOUT_MS / DEFAULT_SLOWLANE_* constants. Resolved
reservation logged at init; under-provisioned (n_vcpus<n_peers) clamp WARNs
loudly, never self-terminates. 8 unit cases, mutation-verified.
This commit is contained in:
Rongsong Shen 2026-06-26 04:58:07 +00:00
parent 295769d8ae
commit 729055a37f
8 changed files with 329 additions and 0 deletions
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23
src/controller/cluster.c
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@ -1342,6 +1342,29 @@ int cluster_init_phase2(cluster_t* c)
c->ha.repl = &c->persist.repl;
INFO("commit engine wired (n_peers=%d, n_vcpus=%d)",
c->ha.n_peers, c->vtaskmgr.n_vcpus);
/* raft-drive-async task 1.1: resolve and log the peer-scaled liveness
* reservation at init — both inputs (n_peers, n_vcpus) are final here.
* Single source of truth: task 1.6 (LivenessAdmission) consumes this
* value, it does NOT recompute the clamp/WARN. */
int liveness_reserved =
drive_async_liveness_reserved(c->ha.n_peers, c->vtaskmgr.n_vcpus);
INFO("drive-async: VTASK_LIVENESS_RESERVED=%d (n_peers=%d, n_vcpus=%d; "
"commit/REQ_BLOCK cap=%d)",
liveness_reserved, c->ha.n_peers, c->vtaskmgr.n_vcpus,
c->vtaskmgr.n_vcpus - liveness_reserved);
if (c->vtaskmgr.n_vcpus < c->ha.n_peers) {
/* Under-provisioned: the n_vcpus ceiling clamped the reservation
* below the ideal n_peers-1. Still correct (deadlock-free via fast
* worker cycling), but operator-visible per CLAUDE.md fail-loud.
* A controller NEVER self-terminates on this condition. */
WARN("drive-async: under-provisioned controller — n_vcpus=%d < "
"n_peers=%d; liveness reservation clamped to %d (ideal %d). "
"Per-peer liveness latency may rise under load; consider "
"raising --vcpus. Cluster remains correct and stays up.",
c->vtaskmgr.n_vcpus, c->ha.n_peers, liveness_reserved,
c->ha.n_peers - 1);
}
}
/* Role set by ha_elect_evaluate_and_signal() inside cluster_run() */