feat: build vehicle data platform and production pipeline

go/vehicle-gateway/internal/metrics/pending.go

@@ -0,0 +1,35 @@
+package metrics
+
+import "sync"
+
+// PendingPairGauge keeps process-wide in-flight totals correct when a service
+// has multiple workers updating the same pair of pending gauges.
+type PendingPairGauge struct {
+	mu     sync.Mutex
+	first  int
+	second int
+}
+
+func (g *PendingPairGauge) Add(registry *Registry, firstMetric string, secondMetric string, firstDelta int, secondDelta int) {
+	if g == nil {
+		return
+	}
+	g.mu.Lock()
+	g.first += firstDelta
+	g.second += secondDelta
+	if g.first < 0 {
+		g.first = 0
+	}
+	if g.second < 0 {
+		g.second = 0
+	}
+	first := g.first
+	second := g.second
+	g.mu.Unlock()
+
+	if registry == nil {
+		return
+	}
+	registry.SetGauge(firstMetric, nil, float64(first))
+	registry.SetGauge(secondMetric, nil, float64(second))
+}