Skill: sse-event-debug

How to triage SSE event divergence in the reservations service.

Problem Patterns

1. Publisher fired event but subscriber didn't receive it
2. Reservation state machine stuck in transition
3. SSE connection drops unexpectedly

Debug Workflow

Step 1: Check SSE Broadcaster State

# Inspect active SSE connections
curl -s http://localhost:3004/api/v1/events/stream?venueId=<id> -H "Authorization: Bearer $TOKEN" &
# In another terminal, check broadcaster internals
node -e "const { getBroadcaster } = require('./dist/services/sse.js'); console.log(getBroadcaster().getStats());"

Step 2: Verify Event Was Published

# Check reservation event log in DB
node -e "const { prisma } = require('./dist/services/database.js'); prisma.reservationEvent.findMany({ orderBy: { createdAt: 'desc' }, take: 10 }).then(console.log);"

Step 3: Inspect Reservation State Machine

// Check current reservation status
const res = await prisma.reservation.findUnique({
  where: { id: reservationId },
  select: { status: true, updatedAt: true },
});
console.log("State:", res.status, "Updated:", res.updatedAt);

State Machine Transitions

PENDING → CONFIRMED (seat guest)
CONFIRMED → COMPLETED (dining finished)
CONFIRMED → CANCELLED (cancelled)
CONFIRMED → NO_SHOW (guest didn't arrive)

Common Fixes

• Missing subscriber: Verify Last-Event-ID header for resumption
• Stale connection: Check exponential backoff (1s, 2s, 4s, ... 30s max)
• Event dedup: Verify event ID is unique and monotonic