Send a presence snapshot before incremental updates
A new client applies deltas to an empty list and misses existing teammates. Add snapshot sequencing at subscription.
- Focused work estimate
- 3h + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Ordering · State synchronization
Estimated field mix
- Real-time systems50%
- Distributed systems50%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
Fictional document team Pine shows collaboration presence for synthetic accounts. Build a loopback WebSocket server and injected clocks; no message content or activity surveillance is required.
Setup prerequisites
- Create synthetic memberships and session identifiers.
- Implement controllable sockets and an in-memory TTL adapter.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- CPRES-101 · Define online presence as an unexpired connection lease
- CPRES-102 · Validate presence room identifiers before subscribing
- CPRES-103 · Scope presence membership checks to each room subscription
- CPRES-104 · Count multiple presence connections without duplicating people
- CPRES-105 · Reject stale presence heartbeats after reconnect
Acceptance criteria
- Snapshot establishes sequence
- Later deltas follow its watermark
- Detected gaps trigger resnapshot
Implementation constraints
- Buffer during snapshot only within a documented limit.
Verification to include
- Join populated room
- Drop one delta and detect gap
Deliverables
- Snapshot handshake and gap cases
Rollout and recovery
Resend full snapshots while delta path is repaired.
Value of the work
For the engineer: Practice ephemeral state, ordering and reconnect semantics.
For the team: Inspect whether online indicators avoid stale or unauthorized claims.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.