Add Prometheus metrics

src/routes/head.go

@@ -7,9 +7,18 @@ import (
 
 	"github.com/mineatar-io/api-server/src/util"
 	"github.com/mineatar-io/skin-render"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
 	"github.com/valyala/fasthttp"
 )
 
+var (
+	renderHeadMetric = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "head_render_count",
+		Help: "The amount of head renders",
+	})
+)
+
 func HeadHandler(ctx *fasthttp.RequestCtx) {
 	user := ctx.UserValue("user").(string)
 
@@ -85,6 +94,8 @@ func HeadHandler(ctx *fasthttp.RequestCtx) {
 		log.Printf("Rendered head image for '%s'\n", uuid)
 	}
 
+	renderHeadMetric.Inc()
+
 	data, err := util.EncodePNG(render)
 
 	if err != nil {