domain.validCandidate hard-requires a non-empty PredictedRTT map, but
CreateQueueTicket persisted an empty one and the only endpoint that
could fill it returned 503 in every real binary, because Service.Probe
was assigned nowhere outside api tests. No client-created ticket could
ever be selected by the matcher. The Godot client had no probe method at
all, so even a wired backend was unreachable from the game.
Four distinct defects had to be fixed for this path to work:
Nothing issued the nonce ProbeProvider was meant to compare against, so
the contract could not be satisfied even in principle. Add
POST /v1/probes/{region}/challenge, backed by a durable single-use
challenge -- durable because any replica may serve the answer for a
challenge another replica issued. RTT is the interval between issuing
and receiving, so no client-reported latency reaches placement.
CreateQueueTicket marshalled a nil map to JSON `null`, a JSONB scalar
rather than an object, and jsonb_set rejects that with "cannot set path
in scalar". RecordProbe would have failed at runtime even once wired.
Persist an object, and normalise non-object values in the update for
rows already written.
A nil ProbeRecorder made the handler report success while persisting
nothing, which silently leaves the ticket unmatchable. That is a
misconfiguration, not a successful probe; it now returns 503.
A successful probe updated PostgreSQL only. The candidate inserted at
enqueue time carries an empty RTT map, and the Redis keyspace has its
TTL continually refreshed, so the stale entry need never repair itself.
Refresh that player's projection after the probe commits.
Client side: add the challenge/answer round trip and have the
matchmaking screen collect evidence before creating a ticket, since
queueing first produces a search that can never match. Probing every
region fully is not required -- placement uses whichever regions
answered -- but queueing with none is refused rather than silently
stalling.
New integration test drives the real enqueue and probe paths and then
asks the actual matcher predicate, rather than hand-building a candidate
the way the unit tests do -- which is exactly why they missed this.
Also make the integration schema reset drop the whole public schema: the
enumerated table list silently broke with each new migration.
Each ten-second queue heartbeat mints a fresh idempotency key and
permanently inserts a row. Published outbox rows and expired/revoked
sessions were never purged either -- the maintenance role performed
lifecycle reconciliation only. At 10,000 queued players heartbeats alone
add roughly 60,000 durable rows per minute, so table and index growth,
vacuum pressure, backup size and recovery time were all unbounded on a
service intended to scale horizontally.
Add retention windows chosen to exceed every retry and recovery horizon
that could still consult the row -- deleting an idempotency key early
would turn a client replay into a second real mutation, so this is a
correctness bound, not just a housekeeping one. Dead-lettered outbox
rows are kept longest, being the record of events never delivered.
Deletes run in bounded SKIP LOCKED batches so a purge never blocks live
traffic, never holds a long transaction, and concurrent maintenance
replicas do not contend. Indexes back each predicate so a pass cannot
degrade into a sequential scan of the table it is bounding. The
maintenance role reports rows purged, the backlog past its window
(deletion lag), and any dead-lettered events.
Also make the migration-rollback test derive its step counts instead of
hardcoding them: adding a migration silently shifted the fixed counts so
the failure surfaced as an unrelated "0006 rollback did not drop
matches.allocation_id".
Closes the last named item on task 8.28 (Health-reclaim): nothing
currently detects or cleans up a match stuck in
ALLOCATING/PROCESS_READY/ASSIGNMENT_READY forever because its server
crashed or was reclaimed by Agones as unhealthy before ever
registering -- players would wait indefinitely for a match that was
never coming.
The design question this was blocked on -- does an abandoned match
auto-requeue its players, or fail and make them re-queue -- isn't
actually open: task 8.50's own stated acceptance criterion already
answers it ("infrastructure-caused cases cannot penalise affected
players"). A server-side crash/reclaim is exactly that, not player
behaviour, so store.ExpireStalledAllocations fails the match but
requeues every participant's ticket to QUEUED with a fresh expiry
(matching the ordinary 30s queue window), releases their
match_participants row (participation_active = false, so they're
matchable again immediately), all inside one FOR UPDATE SKIP LOCKED
pass so a second maintenance replica continues past whatever a
concurrent one is already reclaiming.
Wired into cmd/maintenance alongside the existing season-rollover
sweep: --stalled-allocation-deadline (default 2m) and
--stalled-allocation-batch (default 100).
Covered by a SQL-fragment test and a real PostgreSQL integration test:
two matches (one genuinely stalled, one recent), confirming the
deadline boundary is respected (recent match untouched), both
stranded participants' tickets requeue with a refreshed expiry, the
match_participants row releases, and a second pass doesn't reprocess
an already-FAILED match. Verified clean across 5 runs, plus the full
integration and unit suites.
Josh Creek