Commit c979f6a
feat(meta): DO-based role arbiter replacing Neon cc_node_leases (#131)
* feat(meta): DO-based role arbiter replacing Neon cc_node_leases
ADR-001 elected a meta-orchestrator leader across chittymini-01..06 using
Neon `cc_node_leases`. Two problems with that in practice:
- The daemon runs nowhere. No systemd unit, no daemon/loop process on
chittyserv-vm. The Worker plane being up masks it: the interface is
live while the always-on coordinator is not.
- The fleet it floats across is 6/7 offline (chittymini-01..06 last seen
~7d). chittymini-00 is the operator seat and must not hold persistent
infra, so a leader designed to float has nowhere to float.
A Durable Object is already a strongly-consistent, single-threaded
singleton. Using one does not reimplement leader election — it removes the
need for it, along with the fleet dependency and the Neon lease table.
Neon cost pressure makes this favourable; it would be the right shape
regardless.
CommandCoordinator (meta/coordinator.ts) arbitrates role leases in DO
storage. daemon/coordinator-lease.ts is a drop-in client exporting the same
four functions with identical signatures, so daemon/loop.ts switches by
changing one import. It fails closed with
POLICY_BLOCKED_COORDINATOR_UNAVAILABLE rather than making an unarbitrated
local decision, which would permit split-brain.
Wire semantics are a deliberate 1:1 port of the SQL, preserving both prior
review findings: session ownership required on heartbeat (codex-p2 PR#101
finding-5) and on release (finding-2).
Nodes keep a role as executors that pull work — justified by needing local
filesystem and repo access. Leader election never was that reason.
Tests: 13 cases in real workerd against real DO storage, no mocks. Covers
exclusion, idempotent re-claim, expiry takeover, both session-ownership
rejections, heartbeat extension, release/reclaim, role isolation, lease
clamping, and validation.
Scope: daemon/leader.ts and the Tier-5 Neon usage are untouched. Migrating
those is a separate decision that should be made on spend data.
* fix(meta): address adversarial review of the DO coordinator
Separated review (silent-failure-hunter, fresh context) found three real
defects plus a vacuous test. Split-brain, SQL semantic parity, and auth
came back clean and are unchanged.
P1 — daemon/coordinator-lease.ts could not load on Node. It imported
META_LEADER_ROLE (a value) from meta/coordinator.ts, which evaluates
`cloudflare:workers`. The documented one-line switch in daemon/loop.ts
would have crashed the daemon at module load, before main() and before any
log line: no leader claimed, intent queue silently stopped. tsc passed
because the failure is runtime/bundle-only. Extracted the runtime-free
meta/lease-types.ts; both sides import from it.
Verified: `esbuild --platform=node` fails on the old code with
`Could not resolve "cloudflare:workers"` and succeeds on the new.
P2 — fail-open on partial config. COORDINATOR_URL set with no
COORDINATOR_TOKEN sent unauthenticated requests, drawing a 401 that
loop.ts logs as a claim error and retries forever — a permanently dead
daemon whose logs read like a transient auth blip. Both values are now
required, failing closed with POLICY_BLOCKED_COORDINATOR_UNAVAILABLE.
P3 — greedy path regex. /^.*\/coordinator/ matched the LAST occurrence, so
`/api/meta/coordinator/a/coordinator/release` dispatched `release` from a
path that does not name it. Anchored on the first segment.
Also: a corrupted leaseExpiresAt parsed to NaN, and every NaN comparison is
false, leaving the role permanently unclaimable — a fail-closed deadlock
with no SQL analogue, since Postgres typed the column. Unparseable now
reads as expired.
Tests 13 → 24. The review's sharpest point was that the suite covered the
class and skipped the seam where P1 lived, so this adds a full HTTP surface
suite: path parsing, method switch, 404s, malformed-body 400, the bare-null
describe signal, and the {released} envelope the client unwraps. Plus
MIN-clamp, release-by-other-node, omitted-vs-null sessionId, and corrupt-
expiry recovery.
`extends the expiry on a valid heartbeat` was vacuous — it claimed at 1s and
heartbeat at 60s, so the assertion held by construction and would have
passed against an implementation computing expiry from claimedAt. Rewritten
to use identical leaseSeconds on both calls.
Both new regression tests were mutation-checked: reverting each fix makes
exactly that test fail.
Kept on review advice: claimedAt preserved across takeover. Not a defect —
it reads as "when this role was first continuously held" — and it is
load-bearing, since the client returns null on falsy claimedAt. Comment
corrected to say so.
Not fixed here (pre-existing, outside this diff): daemon/loop.ts:277-295
logs exec_heartbeat_lost on takeover without aborting the in-flight
dispatch, so a demoted leader finishes its current intent alongside the new
one. That is the one real split-brain path and it is unreachable from the
DO.
---------
Co-authored-by: chitcommit <nb@chitty.cc>1 parent d1ac49a commit c979f6a
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