refactor: extract flash out of server.go

internal/buildapi/flash_metrics.go

@@ -0,0 +1,64 @@
+package buildapi
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+const (
+	flashMetricsNamespace = "ado"
+	flashMetricsSubsystem = "flash"
+)
+
+var (
+	// FlashCreatedTotal counts standalone flash operations created via the REST API.
+	FlashCreatedTotal = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: flashMetricsNamespace,
+			Subsystem: flashMetricsSubsystem,
+			Name:      "created_total",
+			Help:      "Total number of flash operations created",
+		},
+	)
+
+	// FlashRequestDuration tracks flash API request duration by endpoint and status code.
+	FlashRequestDuration = prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Namespace: flashMetricsNamespace,
+			Subsystem: flashMetricsSubsystem,
+			Name:      "request_duration_seconds",
+			Help:      "Flash API request duration in seconds",
+			Buckets:   prometheus.DefBuckets,
+		},
+		[]string{"endpoint", "status_code"},
+	)
+)
+
+func init() {
+	prometheus.MustRegister(
+		FlashCreatedTotal,
+		FlashRequestDuration,
+	)
+}
+
+func flashMetricsMiddleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		start := time.Now()
+		c.Next()
+		duration := time.Since(start).Seconds()
+		endpoint := c.FullPath()
+		statusCode := fmt.Sprintf("%d", c.Writer.Status())
+		FlashRequestDuration.WithLabelValues(endpoint, statusCode).Observe(duration)
+	}
+}
+
+func metricsHandler() gin.HandlerFunc {
+	h := promhttp.Handler()
+	return func(c *gin.Context) {
+		h.ServeHTTP(c.Writer, c.Request)
+	}
+}

internal/buildapi/flash_metrics_test.go

@@ -0,0 +1,68 @@
+package buildapi
+
+import (
+	"net/http"
+	"net/http/httptest"
+
+	"github.com/gin-gonic/gin"
+	"github.com/go-logr/logr"
+	. "github.com/onsi/ginkgo/v2" //nolint:revive // Dot import is standard for Ginkgo
+	. "github.com/onsi/gomega"    //nolint:revive // Dot import is standard for Gomega
+	io_prometheus_client "github.com/prometheus/client_model/go"
+)
+
+var _ = Describe("Flash Metrics", func() {
+	var server *APIServer
+
+	BeforeEach(func() {
+		gin.SetMode(gin.TestMode)
+		server = NewAPIServer(":0", logr.Discard())
+	})
+
+	Context("metrics endpoint", func() {
+		It("should expose prometheus metrics at /metrics", func() {
+			// Ensure at least one observation so the histogram appears
+			FlashRequestDuration.WithLabelValues("/v1/flash", "200").Observe(0.001)
+
+			req, err := http.NewRequest("GET", "/metrics", nil)
+			Expect(err).NotTo(HaveOccurred())
+
+			w := httptest.NewRecorder()
+			server.router.ServeHTTP(w, req)
+
+			Expect(w.Code).To(Equal(http.StatusOK))
+			body := w.Body.String()
+			Expect(body).To(ContainSubstring("ado_flash_created_total"))
+			Expect(body).To(ContainSubstring("ado_flash_request_duration_seconds"))
+		})
+	})
+
+	Context("FlashCreatedTotal", func() {
+		It("should increment on flash creation", func() {
+			m := &io_prometheus_client.Metric{}
+			Expect(FlashCreatedTotal.Write(m)).To(Succeed())
+			before := m.GetCounter().GetValue()
+
+			FlashCreatedTotal.Inc()
+
+			m = &io_prometheus_client.Metric{}
+			Expect(FlashCreatedTotal.Write(m)).To(Succeed())
+			after := m.GetCounter().GetValue()
+			Expect(after - before).To(Equal(float64(1)))
+		})
+	})
+
+	Context("FlashRequestDuration", func() {
+		It("should record request duration with endpoint and status labels", func() {
+			FlashRequestDuration.WithLabelValues("/v1/flash", "200").Observe(0.5)
+
+			m := &io_prometheus_client.Metric{}
+			obs, err := FlashRequestDuration.GetMetricWithLabelValues("/v1/flash", "200")
+			Expect(err).NotTo(HaveOccurred())
+			Expect(obs.(interface {
+				Write(*io_prometheus_client.Metric) error
+			}).Write(m)).To(Succeed())
+			Expect(m.GetHistogram().GetSampleCount()).To(BeNumerically(">=", 1))
+		})
+	})
+})