[DRAFT] feat(edge): strengthen edge reporter with metrics, backoff, structured logging

[tanmayxchoudhary]

Summary

Implements the Edge Reporter Module from #24 with a differentiated approach focusing on observability, reliability, and test coverage.

What was implemented

pkg/edge/config.go

• Added StatusInterval, MaxRetries, RetryBaseDelay, EventQueueSize, EventWorkers fields for fine-grained reporter control
• Updated DefaultConfig() with sensible defaults

pkg/edge/metrics.go (NEW)

• In-process Prometheus-friendly metrics collector via expvar (exported as edgereporter)
• Counters: registrations, heartbeats, status reports, events, deliveries (ok/failed), retries, dropped events
• Gauges: queue depth, last delivery status
• Latency ring buffer for recent delivery latency tracking

pkg/edge/reporter.go (Rewritten)

• Exponential backoff with jitter (±50% jitter, doubles each attempt, capped at 30s)
• Structured logging via pkg/logger with component prefix and key-value fields
• Context-aware HTTP requests with timeout propagation
• Separate heartbeat loop (with initial registration + heartbeat on start)
• Separate status loop with configurable interval
• Async event queue with bounded worker pool and non-blocking QueueEvent()
• Graceful drain on shutdown (waits for in-flight events)
• Idempotent Stop() via atomicBool
• Deterministic clock injection for testable timestamps via WithClock() option
• Test hooks via WithHeartbeatHook() / WithStatusHook()
• Backward-compatible StartHeartbeat() alias
• All public methods thread-safe with sync.RWMutex for GeneStatsProvider

pkg/gene/selector.go

• Added deterministic tie-breaker (confidence → verified_by) when scores are equal

How this differs from the 4 existing competing PRs

Feature	PR #20	PR #25	PR #28	PR #31	This PR
Prometheus/expvar metrics	❌	❌	❌	❌	✅
Exponential backoff with jitter	❌ (linear retry)	❌	❌	❌	✅
Structured logging (pkg/logger)	❌ (log.Print)	❌	❌	❌	✅
Context-aware HTTP	❌	❌	❌	❌	✅
Async event queue with worker pool	❌	❌	❌	❌	✅
Separate heartbeat + status loops	❌	❌	❌	❌	✅
Deterministic clock injection	❌	❌	❌	❌	✅
Test hooks for observability	❌	❌	❌	❌	✅
Race-condition tests (-race clean)	❌	❌	❌	❌	✅
Timeout/retry tests	❌	❌	❌	❌	✅
Concurrent access tests	❌	❌	❌	❌	✅
Response body on failure	✅	❌	✅	✅	✅
Bearer auth + X-Clawland-Node-ID	✅	✅	✅	✅	✅
Endpoint normalization	✅	✅	✅	✅	✅
Gene stats in heartbeat/status	✅	❌	✅	✅	✅

Test Results

$ go test -race -count=1 ./pkg/edge/
ok  github.com/sipeed/picoclaw/pkg/edge  2.954s

$ go test -race -count=1 ./pkg/gene/
ok  github.com/sipeed/picoclaw/pkg/gene  1.119s

$ go test ./...
All packages pass (edge, gene, logger)

$ go vet ./...
All clean

Files Changed

• pkg/edge/config.go — extended config with new reporter fields
• pkg/edge/metrics.go — NEW expvar-based metrics collector
• pkg/edge/reporter.go — full rewrite with differentiated features
• pkg/edge/reporter_test.go — NEW 29 tests covering all paths (registration, heartbeat, status, events, queueing, auth headers, endpoint normalization, failure details, retries, timeouts, idempotent stop, concurrent access, metrics)
• pkg/gene/selector.go — deterministic tie-breaker fix

Closes #24