New feature: prometheus metrics endpoint (#46)

2025-11-04 20:59:09 +00:00 · 2025-11-03 18:36:13 +01:00
parent ec1de1fa81
commit e8d3a20781
13 changed files with 564 additions and 82 deletions
--- a/internal/metrics/metrics.go
+++ b/internal/metrics/metrics.go
@@ -0,0 +1,122 @@
+package metrics
+
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+	enabled          bool
+	initOnce         sync.Once
+	requestsTotal    *prometheus.CounterVec
+	requestDuration  *prometheus.HistogramVec
+	requestsInFlight prometheus.Gauge
+	geoLookups       *prometheus.CounterVec
+	portScans        prometheus.Counter
+	dnsQueries       *prometheus.CounterVec
+)
+
+func Enable() {
+	initOnce.Do(func() {
+		enabled = true
+
+		requestsTotal = promauto.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "whatismyip_http_requests_total",
+				Help: "Total number of HTTP requests",
+			},
+			[]string{"method", "path", "status"},
+		)
+
+		requestDuration = promauto.NewHistogramVec(
+			prometheus.HistogramOpts{
+				Name:    "whatismyip_http_request_duration_seconds",
+				Help:    "HTTP request latency in seconds",
+				Buckets: prometheus.DefBuckets,
+			},
+			[]string{"method", "path"},
+		)
+
+		requestsInFlight = promauto.NewGauge(
+			prometheus.GaugeOpts{
+				Name: "whatismyip_http_requests_in_flight",
+				Help: "Current number of HTTP requests being processed",
+			},
+		)
+
+		geoLookups = promauto.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "whatismyip_geo_lookups_total",
+				Help: "Total number of geo lookups",
+			},
+			[]string{"type"},
+		)
+
+		portScans = promauto.NewCounter(
+			prometheus.CounterOpts{
+				Name: "whatismyip_port_scans_total",
+				Help: "Total number of port scan requests",
+			},
+		)
+
+		dnsQueries = promauto.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "whatismyip_dns_queries_total",
+				Help: "Total number of DNS queries",
+			},
+			[]string{"query_type", "rcode"},
+		)
+	})
+}
+
+func GinMiddleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		if !enabled {
+			c.Next()
+			return
+		}
+
+		start := time.Now()
+		path := c.FullPath()
+		if path == "" {
+			path = "/404" // group 404s
+		}
+
+		requestsInFlight.Inc()
+		defer requestsInFlight.Dec()
+
+		c.Next()
+
+		duration := time.Since(start).Seconds()
+		status := c.Writer.Status()
+
+		requestsTotal.WithLabelValues(c.Request.Method, path, fmt.Sprintf("%dxx", status/100)).Inc()
+		requestDuration.WithLabelValues(c.Request.Method, path).Observe(duration)
+	}
+}
+
+func RecordGeoLookup(lookupType string) {
+	if !enabled {
+		return
+	}
+	geoLookups.WithLabelValues(lookupType).Inc()
+}
+
+func RecordPortScan() {
+	if !enabled {
+		return
+	}
+	portScans.Inc()
+}
+
+func RecordDNSQuery(queryType string, rcode string) {
+	if !enabled {
+		return
+	}
+	dnsQueries.WithLabelValues(queryType, rcode).Inc()
+}
--- a/internal/metrics/metrics_test.go
+++ b/internal/metrics/metrics_test.go
@@ -0,0 +1,200 @@
+package metrics
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/prometheus/client_golang/prometheus/testutil"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDisabledMetrics_Middleware(t *testing.T) {
+	if enabled {
+		t.Skip("Skipping disabled test - metrics already enabled")
+	}
+
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+
+	c.Request = httptest.NewRequest("GET", "/test", nil)
+
+	middleware := GinMiddleware()
+
+	assert.NotPanics(t, func() {
+		middleware(c)
+	})
+}
+
+func TestDisabledMetrics_GeoLookup(t *testing.T) {
+	if enabled {
+		t.Skip("Skipping disabled test - metrics already enabled")
+	}
+
+	assert.NotPanics(t, func() {
+		RecordGeoLookup("city")
+	})
+}
+
+func TestDisabledMetrics_PortScan(t *testing.T) {
+	if enabled {
+		t.Skip("Skipping disabled test - metrics already enabled")
+	}
+
+	assert.NotPanics(t, func() {
+		RecordPortScan()
+	})
+}
+
+func TestDisabledMetrics_DNSQuery(t *testing.T) {
+	if enabled {
+		t.Skip("Skipping disabled test - metrics already enabled")
+	}
+
+	assert.NotPanics(t, func() {
+		RecordDNSQuery("A", "NOERROR")
+	})
+}
+
+func TestEnable(t *testing.T) {
+	Enable()
+
+	assert.True(t, enabled, "Enable() should set enabled to true")
+	assert.NotNil(t, requestsTotal, "requestsTotal should be initialized")
+	assert.NotNil(t, requestDuration, "requestDuration should be initialized")
+	assert.NotNil(t, requestsInFlight, "requestsInFlight should be initialized")
+	assert.NotNil(t, geoLookups, "geoLookups should be initialized")
+	assert.NotNil(t, portScans, "portScans should be initialized")
+	assert.NotNil(t, dnsQueries, "dnsQueries should be initialized")
+}
+
+func TestEnableIdempotent(t *testing.T) {
+	Enable()
+	firstRequestsTotal := requestsTotal
+
+	Enable()
+	Enable()
+
+	assert.Equal(t, firstRequestsTotal, requestsTotal, "Enable() should be idempotent")
+}
+
+func TestGinMiddleware_StatusCategories(t *testing.T) {
+	Enable()
+
+	testCases := []struct {
+		status   int
+		category string
+	}{
+		{200, "2xx"},
+		{201, "2xx"},
+		{301, "3xx"},
+		{404, "4xx"},
+		{500, "5xx"},
+	}
+
+	for _, tc := range testCases {
+		gin.SetMode(gin.TestMode)
+		router := gin.New()
+		router.Use(GinMiddleware())
+		router.GET("/test-status", func(c *gin.Context) {
+			c.Status(tc.status)
+		})
+
+		initialCount := testutil.ToFloat64(requestsTotal.WithLabelValues("GET", "/test-status", tc.category))
+
+		w := httptest.NewRecorder()
+		req := httptest.NewRequest("GET", "/test-status", nil)
+		router.ServeHTTP(w, req)
+
+		count := testutil.ToFloat64(requestsTotal.WithLabelValues("GET", "/test-status", tc.category))
+		assert.Equal(t, initialCount+1, count, "Expected count for category %s to increase by 1", tc.category)
+	}
+}
+
+func TestGinMiddleware_404(t *testing.T) {
+	Enable()
+
+	gin.SetMode(gin.TestMode)
+	router := gin.New()
+	router.Use(GinMiddleware())
+
+	initialCount := testutil.ToFloat64(requestsTotal.WithLabelValues("GET", "/404", "4xx"))
+
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "/nonexistent-path", nil)
+	router.ServeHTTP(w, req)
+
+	count := testutil.ToFloat64(requestsTotal.WithLabelValues("GET", "/404", "4xx"))
+	assert.Equal(t, initialCount+1, count, "Expected count to increase by 1 for empty path (404)")
+}
+
+func TestGinMiddleware_RecordsDuration(t *testing.T) {
+	Enable()
+
+	gin.SetMode(gin.TestMode)
+	router := gin.New()
+	router.Use(GinMiddleware())
+	router.GET("/test-duration", func(c *gin.Context) {
+		c.Status(http.StatusOK)
+	})
+
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "/test-duration", nil)
+	router.ServeHTTP(w, req)
+
+	metric := requestDuration.WithLabelValues("GET", "/test-duration")
+	assert.NotNil(t, metric, "Expected histogram metric to exist")
+}
+
+func TestRecordGeoLookup(t *testing.T) {
+	Enable()
+
+	initialCityCount := testutil.ToFloat64(geoLookups.WithLabelValues("city"))
+	initialCountryCount := testutil.ToFloat64(geoLookups.WithLabelValues("asn"))
+
+	RecordGeoLookup("city")
+	RecordGeoLookup("city")
+	RecordGeoLookup("asn")
+
+	cityCount := testutil.ToFloat64(geoLookups.WithLabelValues("city"))
+	assert.Equal(t, initialCityCount+2, cityCount, "Expected city lookups to increase by 2")
+
+	countryCount := testutil.ToFloat64(geoLookups.WithLabelValues("asn"))
+	assert.Equal(t, initialCountryCount+1, countryCount, "Expected country lookups to increase by 1")
+}
+
+func TestRecordPortScan(t *testing.T) {
+	Enable()
+
+	initialCount := testutil.ToFloat64(portScans)
+
+	RecordPortScan()
+	RecordPortScan()
+
+	count := testutil.ToFloat64(portScans)
+	assert.Equal(t, initialCount+2, count, "Expected port scans to increase by 2")
+}
+
+func TestRecordDNSQuery(t *testing.T) {
+	Enable()
+
+	initialACount := testutil.ToFloat64(dnsQueries.WithLabelValues("A", "NOERROR"))
+	initialAAAACount := testutil.ToFloat64(dnsQueries.WithLabelValues("AAAA", "NOERROR"))
+	initialNXDOMAINCount := testutil.ToFloat64(dnsQueries.WithLabelValues("A", "NXDOMAIN"))
+
+	RecordDNSQuery("A", "NOERROR")
+	RecordDNSQuery("A", "NOERROR")
+	RecordDNSQuery("AAAA", "NOERROR")
+	RecordDNSQuery("A", "NXDOMAIN")
+
+	aCount := testutil.ToFloat64(dnsQueries.WithLabelValues("A", "NOERROR"))
+	assert.Equal(t, initialACount+2, aCount, "Expected A NOERROR queries to increase by 2")
+
+	aaaaCount := testutil.ToFloat64(dnsQueries.WithLabelValues("AAAA", "NOERROR"))
+	assert.Equal(t, initialAAAACount+1, aaaaCount, "Expected AAAA NOERROR queries to increase by 1")
+
+	nxdomainCount := testutil.ToFloat64(dnsQueries.WithLabelValues("A", "NXDOMAIN"))
+	assert.Equal(t, initialNXDOMAINCount+1, nxdomainCount, "Expected A NXDOMAIN queries to increase by 1")
+}