feat: prometheus metrics

internal/metrics/metrics.go

@@ -0,0 +1,50 @@
+package metrics
+
+import (
+	"github.com/gorilla/mux"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+var (
+	pasteLengthHistogram = promauto.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Namespace: "goblin",
+			Subsystem: "paste",
+			Name:      "length",
+			Help:      "Length of pastes",
+			Buckets:   prometheus.ExponentialBuckets(1, 2, 10), // Example buckets
+		},
+		[]string{"status"}, // Labels for success/failure
+	)
+
+	pasteCreatedCounter = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: "goblin",
+			Subsystem: "paste",
+			Name:      "created_total",
+			Help:      "Total number of pastes created",
+		},
+		[]string{"status"}, // Labels for success/failure
+	)
+)
+
+// ObservePasteLength records the length of pastes.
+func ObservePasteLength(status string, length float64) {
+	pasteLengthHistogram.WithLabelValues(status).Observe(length)
+}
+
+// IncrementPasteCreatedCounter increments the paste creation counter.
+func IncrementPasteCreatedCounter(status string) {
+	pasteCreatedCounter.WithLabelValues(status).Inc()
+}
+
+// InitPrometheus initializes Prometheus metrics and registers a handler for /metrics endpoint.
+func InitPrometheus(router *mux.Router) {
+	// Register Prometheus metrics collectors here
+	// For example, you can use promauto to define and register metrics
+
+	// Register Prometheus HTTP handler for /metrics endpoint with the Mux router
+	router.Handle("/metrics", promhttp.Handler())
+}

internal/paste/paste.go

@@ -8,9 +8,9 @@ import (
 	"net/http"
 	"os"
 	"path/filepath"
-	"strings"
 	"time"
 
+	"goblin/internal/metrics"
 	"goblin/internal/util"
 
 	"github.com/gorilla/mux"
@@ -62,6 +62,7 @@ func CreatePasteHandler(w http.ResponseWriter, r *http.Request) {
 	content, err := io.ReadAll(r.Body)
 	if err != nil {
 		http.Error(w, "Failed to read request body", http.StatusBadRequest)
+		metrics.IncrementPasteCreatedCounter("failure")
 		return
 	}
 
@@ -96,6 +97,7 @@ func CreatePasteHandler(w http.ResponseWriter, r *http.Request) {
 	if err := util.CreateDirectoryIfNotExists(pasteDir); err != nil {
 		logger.Errorf("Failed to create paste directory: %v", err)
 		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		metrics.IncrementPasteCreatedCounter("failure")
 		return
 	}
 
@@ -105,6 +107,7 @@ func CreatePasteHandler(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		logger.Errorf("Failed to create paste file: %v", err)
 		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		metrics.IncrementPasteCreatedCounter("failure")
 		return
 	}
 	defer pasteFile.Close()
@@ -114,32 +117,38 @@ func CreatePasteHandler(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		logger.Errorf("Failed to write paste content to file: %v", err)
 		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		metrics.IncrementPasteCreatedCounter("failure")
 		return
 	}
 
-	// Determine the protocol based on the request's TLS connection
-	protocol := "http"
+	// Construct the complete paste URL including the protocol
+	var protocol string
 	if r.TLS != nil {
 		protocol = "https"
+	} else {
+		protocol = "http"
 	}
-
-	// Construct the complete paste URL with the protocol
 	pasteURL := fmt.Sprintf("%s://%s/%s", protocol, r.Host, pasteID)
 
-	// Remove any trailing '%' character from the pasteURL
-	if strings.HasSuffix(pasteURL, "%") {
-		pasteURL = pasteURL[:len(pasteURL)-1]
-	}
-
 	// Write the paste URL in the response
 	response := fmt.Sprintf("Paste available at %s", pasteURL)
 	w.Write([]byte(response))
+
+	// Record metrics
+	metrics.IncrementPasteCreatedCounter("success")
+	metrics.ObservePasteLength("success", float64(len(content)))
 }
 
 func GetPasteHandler(w http.ResponseWriter, r *http.Request) {
 	vars := mux.Vars(r)
 	pasteID := vars["id"]
 
+	// Exclude the "/metrics" path
+	if pasteID == "metrics" {
+		http.NotFound(w, r)
+		return
+	}
+
 	p, exists := pasteMap[pasteID]
 	if !exists {
 		http.Error(w, "Paste not found", http.StatusNotFound)

internal/router/router.go

@@ -9,7 +9,9 @@ import (
 
 func NewRouter() http.Handler {
 	r := mux.NewRouter()
+
 	r.HandleFunc("/", paste.CreatePasteHandler).Methods("POST")
 	r.HandleFunc("/{id}", paste.GetPasteHandler).Methods("GET")
+
 	return r
 }