feat: integrate Prometheus metrics for HTTP requests and worker performance

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/joho/godotenv v1.5.1
 	github.com/knadh/koanf/providers/env v1.1.0
 	github.com/knadh/koanf/v2 v2.3.4
+	github.com/prometheus/client_golang v1.23.2
 	github.com/redis/go-redis/v9 v9.18.0
 	github.com/stretchr/testify v1.11.1
 	github.com/swaggo/http-swagger v1.3.4
@@ -25,6 +26,7 @@ require (
 	github.com/Azure/go-ansiterm v0.0.0-20250102033503-faa5f7b0171c // indirect
 	github.com/KyleBanks/depth v1.2.1 // indirect
 	github.com/Microsoft/go-winio v0.6.2 // indirect
+	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cenkalti/backoff/v4 v4.3.0 // indirect
 	github.com/cenkalti/backoff/v5 v5.0.3 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
@@ -73,11 +75,15 @@ require (
 	github.com/moby/sys/userns v0.1.0 // indirect
 	github.com/moby/term v0.5.2 // indirect
 	github.com/morikuni/aec v1.0.0 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/opencontainers/go-digest v1.0.0 // indirect
 	github.com/opencontainers/image-spec v1.1.1 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/power-devops/perfstat v0.0.0-20240221224432-82ca36839d55 // indirect
+	github.com/prometheus/client_model v0.6.2 // indirect
+	github.com/prometheus/common v0.66.1 // indirect
+	github.com/prometheus/procfs v0.16.1 // indirect
 	github.com/shirou/gopsutil/v4 v4.26.2 // indirect
 	github.com/sirupsen/logrus v1.9.3 // indirect
 	github.com/stretchr/objx v0.5.2 // indirect
@@ -94,6 +100,7 @@ require (
 	go.opentelemetry.io/otel/trace v1.43.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.10.0 // indirect
 	go.uber.org/atomic v1.11.0 // indirect
+	go.yaml.in/yaml/v2 v2.4.2 // indirect
 	golang.org/x/mod v0.33.0 // indirect
 	golang.org/x/net v0.51.0 // indirect
 	golang.org/x/sys v0.42.0 // indirect

go.sum

@@ -8,6 +8,8 @@ github.com/KyleBanks/depth v1.2.1 h1:5h8fQADFrWtarTdtDudMmGsC7GPbOAu6RVB3ffsVFHc
 github.com/KyleBanks/depth v1.2.1/go.mod h1:jzSb9d0L43HxTQfT+oSA1EEp2q+ne2uh6XgeJcm8brE=
 github.com/Microsoft/go-winio v0.6.2 h1:F2VQgta7ecxGYO8k3ZZz3RS8fVIXVxONVUPlNERoyfY=
 github.com/Microsoft/go-winio v0.6.2/go.mod h1:yd8OoFMLzJbo9gZq8j5qaps8bJ9aShtEA8Ipt1oGCvU=
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/bsm/ginkgo/v2 v2.12.0 h1:Ny8MWAHyOepLGlLKYmXG4IEkioBysk6GpaRTLC8zwWs=
 github.com/bsm/ginkgo/v2 v2.12.0/go.mod h1:SwYbGRRDovPVboqFv0tPTcG1sN61LM1Z4ARdbAV9g4c=
 github.com/bsm/gomega v1.27.10 h1:yeMWxP2pV2fG3FgAODIY8EiRE3dy0aeFYt4l7wh6yKA=
@@ -117,6 +119,8 @@ github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
+github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
 github.com/leodido/go-urn v1.4.0 h1:WT9HwE9SGECu3lg4d/dIA+jxlljEa1/ffXKmRjqdmIQ=
 github.com/leodido/go-urn v1.4.0/go.mod h1:bvxc+MVxLKB4z00jd1z+Dvzr47oO32F/QSNjSBOlFxI=
 github.com/lufia/plan9stats v0.0.0-20211012122336-39d0f177ccd0 h1:6E+4a0GO5zZEnZ81pIr0yLvtUWk2if982qA3F3QD6H4=
@@ -150,6 +154,8 @@ github.com/moby/term v0.5.2 h1:6qk3FJAFDs6i/q3W/pQ97SX192qKfZgGjCQqfCJkgzQ=
 github.com/moby/term v0.5.2/go.mod h1:d3djjFCrjnB+fl8NJux+EJzu0msscUP+f8it8hPkFLc=
 github.com/morikuni/aec v1.0.0 h1:nP9CBfwrvYnBRgY6qfDQkygYDmYwOilePFkwzv4dU8A=
 github.com/morikuni/aec v1.0.0/go.mod h1:BbKIizmSmc5MMPqRYbxO4ZU0S0+P200+tUnFx7PXmsc=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
 github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e/go.mod h1:zD1mROLANZcx1PVRCS0qkT7pwLkGfwJo4zjcN/Tysno=
 github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8Oi/yOhh5U=
 github.com/opencontainers/go-digest v1.0.0/go.mod h1:0JzlMkj0TRzQZfJkVvzbP0HBR3IKzErnv2BNG4W4MAM=
@@ -161,6 +167,14 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/power-devops/perfstat v0.0.0-20240221224432-82ca36839d55 h1:o4JXh1EVt9k/+g42oCprj/FisM4qX9L3sZB3upGN2ZU=
 github.com/power-devops/perfstat v0.0.0-20240221224432-82ca36839d55/go.mod h1:OmDBASR4679mdNQnz2pUhc2G8CO2JrUAVFDRBDP/hJE=
+github.com/prometheus/client_golang v1.23.2 h1:Je96obch5RDVy3FDMndoUsjAhG5Edi49h0RJWRi/o0o=
+github.com/prometheus/client_golang v1.23.2/go.mod h1:Tb1a6LWHB3/SPIzCoaDXI4I8UHKeFTEQ1YCr+0Gyqmg=
+github.com/prometheus/client_model v0.6.2 h1:oBsgwpGs7iVziMvrGhE53c/GrLUsZdHnqNwqPLxwZyk=
+github.com/prometheus/client_model v0.6.2/go.mod h1:y3m2F6Gdpfy6Ut/GBsUqTWZqCUvMVzSfMLjcu6wAwpE=
+github.com/prometheus/common v0.66.1 h1:h5E0h5/Y8niHc5DlaLlWLArTQI7tMrsfQjHV+d9ZoGs=
+github.com/prometheus/common v0.66.1/go.mod h1:gcaUsgf3KfRSwHY4dIMXLPV0K/Wg1oZ8+SbZk/HH/dA=
+github.com/prometheus/procfs v0.16.1 h1:hZ15bTNuirocR6u0JZ6BAHHmwS1p8B4P6MRqxtzMyRg=
+github.com/prometheus/procfs v0.16.1/go.mod h1:teAbpZRB1iIAJYREa1LsoWUXykVXA1KlTmWl8x/U+Is=
 github.com/redis/go-redis/v9 v9.18.0 h1:pMkxYPkEbMPwRdenAzUNyFNrDgHx9U+DrBabWNfSRQs=
 github.com/redis/go-redis/v9 v9.18.0/go.mod h1:k3ufPphLU5YXwNTUcCRXGxUoF1fqxnhFQmscfkCoDA0=
 github.com/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0tI/otEQ=
@@ -214,6 +228,10 @@ go.opentelemetry.io/proto/otlp v1.10.0 h1:IQRWgT5srOCYfiWnpqUYz9CVmbO8bFmKcwYxpu
 go.opentelemetry.io/proto/otlp v1.10.0/go.mod h1:/CV4QoCR/S9yaPj8utp3lvQPoqMtxXdzn7ozvvozVqk=
 go.uber.org/atomic v1.11.0 h1:ZvwS0R+56ePWxUNi+Atn9dWONBPp/AUETXlHW0DxSjE=
 go.uber.org/atomic v1.11.0/go.mod h1:LUxbIzbOniOlMKjJjyPfpl4v+PKK2cNJn91OQbhoJI0=
+go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
+go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
+go.yaml.in/yaml/v2 v2.4.2 h1:DzmwEr2rDGHl7lsFgAHxmNz/1NlQ7xLIrlN2h5d1eGI=
+go.yaml.in/yaml/v2 v2.4.2/go.mod h1:081UH+NErpNdqlCXm3TtEran0rJZGxAYx9hb/ELlsPU=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/crypto v0.49.0 h1:+Ng2ULVvLHnJ/ZFEq4KdcDd/cfjrrjjNSXNzxg0Y4U4=

internal/api/middleware.go

@@ -6,11 +6,14 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"strconv"
 	"strings"
 	"time"
 
 	"github.com/DanielPopoola/fairqueue/internal/auth"
+	"github.com/DanielPopoola/fairqueue/internal/metrics"
 	redisstore "github.com/DanielPopoola/fairqueue/internal/store/redis"
+	"github.com/go-chi/chi/v5"
 )
 
 const otpTTL = 10 * time.Minute
@@ -107,3 +110,34 @@ func generateOTP() (string, error) {
 	n := (int(b[0])<<16 | int(b[1])<<8 | int(b[2])) % 1_000_000
 	return fmt.Sprintf("%06d", n), nil
 }
+
+func MetricsMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+
+		// Wrap ResponseWriter to capture status code
+		wrapped := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
+		next.ServeHTTP(wrapped, r)
+
+		duration := time.Since(start).Seconds()
+		status := strconv.Itoa(wrapped.status)
+
+		routePattern := chi.RouteContext(r.Context()).RoutePattern()
+		if routePattern == "" {
+			routePattern = r.URL.Path
+		}
+
+		metrics.HTTPRequestsTotal.WithLabelValues(r.Method, routePattern, status).Inc()
+		metrics.HTTPRequestDuration.WithLabelValues(r.Method, routePattern).Observe(duration)
+	})
+}
+
+type statusRecorder struct {
+	http.ResponseWriter
+	status int
+}
+
+func (r *statusRecorder) WriteHeader(status int) {
+	r.status = status
+	r.ResponseWriter.WriteHeader(status)
+}

internal/api/server.go

@@ -23,6 +23,7 @@ import (
 	"github.com/DanielPopoola/fairqueue/internal/auth"
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	httpSwagger "github.com/swaggo/http-swagger"
 )
 
@@ -37,6 +38,10 @@ func NewRouter(
 	r.Use(middleware.RequestID)
 	r.Use(middleware.RealIP)
 	r.Use(middleware.Recoverer)
+	r.Use(middleware.RequestID)
+	r.Use(middleware.RealIP)
+	r.Use(middleware.Recoverer)
+	r.Use(MetricsMiddleware)
 
 	// Swagger UI — served at /swagger/index.html
 	r.Get("/swagger/*", httpSwagger.Handler(
@@ -50,6 +55,7 @@ func NewRouter(
 	r.Post("/auth/customer/otp/verify", h.VerifyOTP)
 	r.Get("/events/{eventId}", h.GetEvent)
 	r.Post("/webhooks/paystack", h.PaystackWebhook)
+	r.Handle("/metrics", promhttp.Handler())
 
 	// ── Organizer-protected routes ────────────────────────────
 	r.Group(func(r chi.Router) {

internal/metrics/metrics.go

@@ -0,0 +1,54 @@
+package metrics
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+	// HTTP metrics
+	HTTPRequestsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "fairqueue_http_requests_total",
+		Help: "Total HTTP requests by method, path, and status code",
+	}, []string{"method", "path", "status"})
+
+	HTTPRequestDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Name:    "fairqueue_http_request_duration_seconds",
+		Help:    "HTTP request duration in seconds",
+		Buckets: prometheus.DefBuckets,
+	}, []string{"method", "path"})
+
+	// Queue metrics
+	QueueWaitingTotal = promauto.NewGaugeVec(prometheus.GaugeOpts{
+		Name: "fairqueue_queue_waiting_total",
+		Help: "Number of customers currently waiting in queue per event",
+	}, []string{"event_id"})
+
+	QueueAdmittedTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "fairqueue_queue_admitted_total",
+		Help: "Total customers admitted from queue",
+	}, []string{"event_id"})
+
+	// Claim metrics
+	ClaimsCreatedTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "fairqueue_claims_created_total",
+		Help: "Total claims created",
+	}, []string{"event_id"})
+
+	ClaimsExpiredTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "fairqueue_claims_expired_total",
+		Help: "Total claims expired without payment",
+	}, []string{"event_id"})
+
+	// Worker metrics
+	WorkerTickDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Name:    "fairqueue_worker_tick_duration_seconds",
+		Help:    "Time taken per worker tick",
+		Buckets: prometheus.DefBuckets,
+	}, []string{"worker"})
+
+	WorkerTickErrors = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "fairqueue_worker_tick_errors_total",
+		Help: "Total worker tick errors",
+	}, []string{"worker"})
+)

internal/worker/admission.go

@@ -4,10 +4,12 @@ import (
 	"context"
 	"fmt"
 	"log/slog"
+	"time"
 
 	"github.com/DanielPopoola/fairqueue/internal/auth"
 	"github.com/DanielPopoola/fairqueue/internal/config"
 	"github.com/DanielPopoola/fairqueue/internal/domain"
+	"github.com/DanielPopoola/fairqueue/internal/metrics"
 	"github.com/DanielPopoola/fairqueue/internal/service"
 	postgres "github.com/DanielPopoola/fairqueue/internal/store/postgres"
 )
@@ -53,6 +55,10 @@ func NewAdmissionWorker(
 }
 
 func (w *AdmissionWorker) Run(ctx context.Context) error {
+	start := time.Now()
+	defer func() {
+		metrics.WorkerTickDuration.WithLabelValues("admission").Observe(time.Since(start).Seconds())
+	}()
 	events, err := w.events.GetByStatus(ctx, domain.EventStatusActive)
 	if err != nil {
 		return fmt.Errorf("fetching active events: %w", err)
@@ -128,6 +134,7 @@ func (w *AdmissionWorker) calculateBatchSize(ctx context.Context, event *domain.
 // notifyAdmitted generates a signed admission token for each admitted
 // customer and sends it to them.
 func (w *AdmissionWorker) notifyAdmitted(ctx context.Context, eventID string, customerIDs []string) error {
+	metrics.QueueAdmittedTotal.WithLabelValues(eventID).Add(float64(len(customerIDs)))
 	for _, customerID := range customerIDs {
 		token, err := w.tokenizer.Generate(customerID, eventID)
 		if err != nil {

internal/worker/expiry.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/DanielPopoola/fairqueue/internal/config"
 	"github.com/DanielPopoola/fairqueue/internal/domain"
+	"github.com/DanielPopoola/fairqueue/internal/metrics"
 	"github.com/DanielPopoola/fairqueue/internal/service"
 	postgres "github.com/DanielPopoola/fairqueue/internal/store/postgres"
 )
@@ -89,6 +90,7 @@ func (w *ExpiryWorker) releaseClaim(ctx context.Context, claim *domain.Claim) er
 		return fmt.Errorf("releasing claim: %w", err)
 	}
 
+	metrics.ClaimsExpiredTotal.WithLabelValues(claim.EventID).Inc()
 	// Postgres committed — now restore inventory in Redis.
 	// Non-fatal: reconciliation worker heals any divergence.
 	if err := w.inventory.Increment(ctx, claim.EventID); err != nil {