prometheus metrics

Author: hunterlong

handlers.go

@@ -33,6 +33,8 @@ func ConfirmHandler(w http.ResponseWriter, r *http.Request) {
 		Email:   user.Email,
 		Message: "email address is now confirmed",
 	}
+
+	confirmations++
 	sendJSON(w, response)
 }
 
@@ -53,6 +55,7 @@ func UnsubscribeHandler(w http.ResponseWriter, r *http.Request) {
 		Message: "email has been unsubscribed",
 	}
 
+	unsubscribed++
 	sendJSON(w, status)
 }
 
@@ -107,9 +110,11 @@ func SendHandler(w http.ResponseWriter, r *http.Request) {
 
 	err = SendEmail(user)
 	if err != nil {
+		emailErrors++
 		sendError(w, err)
 		return
 	}
+	emailsSent++
 }
 
 func RequestHandler(w http.ResponseWriter, r *http.Request) {
@@ -149,6 +154,7 @@ func RequestHandler(w http.ResponseWriter, r *http.Request) {
 		Message: "check email",
 	}
 
+	requests++
 	sendJSON(w, response)
 }
 

main.go

@@ -33,6 +33,7 @@ func main() {
 	r.HandleFunc("/resend", ResendHandler).Methods("GET")
 	r.HandleFunc("/unsubscribe", UnsubscribeHandler).Methods("GET")
 	r.HandleFunc("/send", SendHandler).Methods("POST")
+	r.HandleFunc("/metrics", MetricsHandler)
 	http.ListenAndServe(":8000", r)
 }
 

metrics.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+var (
+	emailsSent    int
+	emailErrors   int
+	requests      int
+	confirmations int
+	unsubscribed  int
+)
+
+func MetricsHandler(w http.ResponseWriter, r *http.Request) {
+	var out []string
+	out = append(out, fmt.Sprintf("email_sent %d", emailsSent))
+	out = append(out, fmt.Sprintf("email_errors %d", emailErrors))
+	out = append(out, fmt.Sprintf("requests %d", requests))
+	out = append(out, fmt.Sprintf("confirmations %d", confirmations))
+	out = append(out, fmt.Sprintf("unsubscribed %d", unsubscribed))
+	w.Write([]byte(strings.Join(out, "\n")))
+	w.WriteHeader(http.StatusOK)
+}