From 0892c33b134b32e0808f0d6756e73400b19584c9 Mon Sep 17 00:00:00 2001
From: Jonas <jonas@jjsoftware.dk>
Date: Wed, 29 Apr 2026 15:38:06 +0200
Subject: [PATCH] feat: metrics, makefile

---
 projects/greenlight/Makefile              | 34 +++++++++++++++++++++++
 projects/greenlight/cmd/api/middleware.go | 34 +++++++++++++++++++++++
 projects/greenlight/cmd/api/routes.go     |  2 +-
 projects/greenlight/go.mod                |  1 +
 projects/greenlight/go.sum                |  2 ++
 5 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/projects/greenlight/Makefile b/projects/greenlight/Makefile
index e69de29..4456ccb 100644
--- a/projects/greenlight/Makefile
+++ b/projects/greenlight/Makefile
@@ -0,0 +1,34 @@
+include .env
+
+## help: print this help message
+.PHONY: help
+help:
+	@echo 'Usage:'
+	@sed -n 's/^##//p' ${MAKEFILE_LIST} | column -t -s ':' |  sed -e 's/^/ /'
+
+.PHONY: confirm
+confirm:
+	@echo -n 'Are you sure? [y/N] ' && read ans && [ $${ans:-N} = y ]
+
+## run/api: run the cmd/api application
+.PHONY: run/api
+run/api:
+	go run ./cmd/api -db-dsn=${DATABASE_DSN}
+
+## db/psql: connect to the database using psql
+.PHONY: db/psql
+db/psql:
+	psql ${DATABASE_DSN}
+
+## db/migrations/new name=$1: create a new database migration
+.PHONY: db/migrations/new
+db/migrations/new:
+	@echo 'Creating migration files for ${name}...'
+	migrate create -seq -ext=.sql -dir=./migrations ${name}
+
+## db/migrations/up: apply all up database migrations
+.PHONY: db/migrations/up
+db/migrations/up: confirm
+	@echo 'Running up migrations...'
+	migrate -path ./migrations -database ${DATABASE_DSN} up
+
diff --git a/projects/greenlight/cmd/api/middleware.go b/projects/greenlight/cmd/api/middleware.go
index 292a52a..d016242 100644
--- a/projects/greenlight/cmd/api/middleware.go
+++ b/projects/greenlight/cmd/api/middleware.go
@@ -2,13 +2,16 @@ package main
 
 import (
 	"errors"
+	"expvar"
 	"fmt"
 	"net"
 	"net/http"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
 
+	"github.com/felixge/httpsnoop"
 	"golang.org/x/time/rate"
 	"greenlight.debuggingjon.dev/internal/data"
 	"greenlight.debuggingjon.dev/internal/validator"
@@ -280,3 +283,34 @@ func (app *application) enableCORS(next http.Handler) http.Handler {
 		next.ServeHTTP(w, r)
 	})
 }
+
+func (app *application) metrics(next http.Handler) http.Handler {
+	totalRequestsReceived := expvar.NewInt("total_requests_received")
+	totalResponsesSent := expvar.NewInt("total_responses_sent")
+	totalProcessingTimeMicroseconds := expvar.NewInt("total_processing_time_μs")
+	// Declare a new expvar map to hold the count of responses for each HTTP status
+	// code.
+	totalResponsesSentByStatus := expvar.NewMap("total_responses_sent_by_status")
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Increment the requests received count, like before.
+		totalRequestsReceived.Add(1)
+
+		// Call the httpsnoop.CaptureMetrics() function, passing in the next handler in
+		// the chain along with the existing http.ResponseWriter and http.Request. This
+		// returns the metrics struct that we saw above.
+		metrics := httpsnoop.CaptureMetrics(next, w, r)
+
+		// Increment the response sent count, like before.
+		totalResponsesSent.Add(1)
+
+		// Get the request processing time in microseconds from httpsnoop and increment
+		// the cumulative processing time.
+		totalProcessingTimeMicroseconds.Add(metrics.Duration.Microseconds())
+
+		// Use the Add() method to increment the count for the given status code by 1.
+		// Note that the expvar map is string-keyed, so we need to use the strconv.Itoa()
+		// function to convert the status code (which is an integer) to a string.
+		totalResponsesSentByStatus.Add(strconv.Itoa(metrics.Code), 1)
+	})
+}
diff --git a/projects/greenlight/cmd/api/routes.go b/projects/greenlight/cmd/api/routes.go
index 00fa5b8..dbc9dec 100644
--- a/projects/greenlight/cmd/api/routes.go
+++ b/projects/greenlight/cmd/api/routes.go
@@ -31,5 +31,5 @@ func (app *application) routes() http.Handler {
 	// Register a new GET /debug/vars endpoint pointing to the expvar handler.
 	router.Handler(http.MethodGet, "/debug/vars", expvar.Handler())
 
-	return app.recoverPanic(app.enableCORS(app.rateLimit(app.authenticate(router))))
+	return app.metrics(app.recoverPanic(app.enableCORS(app.rateLimit(app.authenticate(router)))))
 }
diff --git a/projects/greenlight/go.mod b/projects/greenlight/go.mod
index 1e0254a..4b78c26 100644
--- a/projects/greenlight/go.mod
+++ b/projects/greenlight/go.mod
@@ -11,6 +11,7 @@ require (
 )
 
 require (
+	github.com/felixge/httpsnoop v1.0.1 // indirect
 	github.com/go-mail/mail/v2 v2.3.0 // indirect
 	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
 )
diff --git a/projects/greenlight/go.sum b/projects/greenlight/go.sum
index 9d9d661..e8f00b2 100644
--- a/projects/greenlight/go.sum
+++ b/projects/greenlight/go.sum
@@ -1,3 +1,5 @@
+github.com/felixge/httpsnoop v1.0.1 h1:lvB5Jl89CsZtGIWuTcDM1E/vkVs49/Ml7JJe07l8SPQ=
+github.com/felixge/httpsnoop v1.0.1/go.mod h1:m8KPJKqk1gH5J9DgRY2ASl2lWCfGKXixSwevea8zH2U=
 github.com/go-mail/mail/v2 v2.3.0 h1:wha99yf2v3cpUzD1V9ujP404Jbw2uEvs+rBJybkdYcw=
 github.com/go-mail/mail/v2 v2.3.0/go.mod h1:oE2UK8qebZAjjV1ZYUpY7FPnbi/kIU53l1dmqPRb4go=
 github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=