Adding OpenTelemetry Metrics and Tracing

internal/state/telemetry_view.go

@@ -0,0 +1,80 @@
+package state
+
+import (
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/fosrl/newt/internal/telemetry"
+)
+
+// TelemetryView is a minimal, thread-safe implementation to feed observables.
+// Since one Newt process represents one site, we expose a single logical site.
+// site_id is a resource attribute, so we do not emit per-site labels here.
+type TelemetryView struct {
+	online     atomic.Bool
+	lastHBUnix atomic.Int64 // unix seconds
+	// per-tunnel sessions
+	sessMu   sync.RWMutex
+	sessions map[string]*atomic.Int64
+}
+
+var (
+	globalView atomic.Pointer[TelemetryView]
+)
+
+// Global returns a singleton TelemetryView.
+func Global() *TelemetryView {
+	if v := globalView.Load(); v != nil { return v }
+	v := &TelemetryView{ sessions: make(map[string]*atomic.Int64) }
+	globalView.Store(v)
+	telemetry.RegisterStateView(v)
+	return v
+}
+
+// Instrumentation helpers
+func (v *TelemetryView) IncSessions(tunnelID string) {
+	v.sessMu.Lock(); defer v.sessMu.Unlock()
+	c := v.sessions[tunnelID]
+	if c == nil { c = &atomic.Int64{}; v.sessions[tunnelID] = c }
+	c.Add(1)
+}
+func (v *TelemetryView) DecSessions(tunnelID string) {
+	v.sessMu.Lock(); defer v.sessMu.Unlock()
+	if c := v.sessions[tunnelID]; c != nil {
+		c.Add(-1)
+		if c.Load() <= 0 { delete(v.sessions, tunnelID) }
+	}
+}
+func (v *TelemetryView) ClearTunnel(tunnelID string) {
+	v.sessMu.Lock(); defer v.sessMu.Unlock()
+	delete(v.sessions, tunnelID)
+}
+func (v *TelemetryView) SetOnline(b bool) { v.online.Store(b) }
+func (v *TelemetryView) TouchHeartbeat() { v.lastHBUnix.Store(time.Now().Unix()) }
+
+// --- telemetry.StateView interface ---
+
+func (v *TelemetryView) ListSites() []string { return []string{"self"} }
+func (v *TelemetryView) Online(_ string) (bool, bool) { return v.online.Load(), true }
+func (v *TelemetryView) LastHeartbeat(_ string) (time.Time, bool) {
+	sec := v.lastHBUnix.Load()
+	if sec == 0 { return time.Time{}, false }
+	return time.Unix(sec, 0), true
+}
+func (v *TelemetryView) ActiveSessions(_ string) (int64, bool) {
+	// aggregated sessions (not used for per-tunnel gauge)
+	v.sessMu.RLock(); defer v.sessMu.RUnlock()
+	var sum int64
+	for _, c := range v.sessions { if c != nil { sum += c.Load() } }
+	return sum, true
+}
+
+// Extended accessor used by telemetry callback to publish per-tunnel samples.
+func (v *TelemetryView) SessionsByTunnel() map[string]int64 {
+	v.sessMu.RLock(); defer v.sessMu.RUnlock()
+	out := make(map[string]int64, len(v.sessions))
+	for id, c := range v.sessions { if c != nil && c.Load() > 0 { out[id] = c.Load() } }
+	return out
+}
+