wip: test http handler CT generation

Signed-off-by: Arthur Silva Sens <arthur.sens@coralogix.com>

prometheus/promhttp/http.go

@@ -379,6 +379,9 @@ type HandlerOpts struct {
 	// NOTE: This feature is experimental and not covered by OpenMetrics or Prometheus
 	// exposition format.
 	ProcessStartTime time.Time
+	// If true, Counters, Summaries and Histograms will be exposed with additional 
+	// information about the timestamp when a particular timeseries was first initialized.
+	EnableCreatedTimestamps bool
 }
 
 // gzipAccepted returns whether the client will accept gzip-encoded content.

prometheus/promhttp/http_test.go

@@ -17,6 +17,7 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"io"
 	"log"
 	"net/http"
 	"net/http/httptest"
@@ -25,6 +26,7 @@ import (
 	"time"
 
 	dto "github.com/prometheus/client_model/go"
+	"google.golang.org/protobuf/proto"
 
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -331,3 +333,57 @@ func TestHandlerTimeout(t *testing.T) {
 
 	close(c.Block) // To not leak a goroutine.
 }
+
+func TestHandlerWithCreatedTimestamps(t *testing.T) {
+	testCases := []struct {
+		testName                string
+		enableCreatedTimestamps bool
+	}{
+		{
+			testName:                "Created timestamps enabled",
+			enableCreatedTimestamps: true,
+		},
+		{
+			testName:                "Created timestamps disabled",
+			enableCreatedTimestamps: false,
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.testName, func(t *testing.T) {
+			reg := prometheus.NewRegistry()
+			handler := HandlerFor(reg, HandlerOpts{EnableCreatedTimestamps: true})
+			w := httptest.NewRecorder()
+			counter := prometheus.NewCounterVec(prometheus.CounterOpts{
+				Name: "test",
+				Help: "help test",
+			}, []string{"label"})
+			reg.MustRegister(counter)
+			counter.WithLabelValues("test1").Inc()
+			counter.WithLabelValues("test2").Add(2)
+			request, _ := http.NewRequest("GET", "/", nil)
+			request.Header.Add("Accept", "application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited;q=0.8")
+
+			handler.ServeHTTP(w, request)
+			rsp := w.Result()
+			body, err := io.ReadAll(rsp.Body)
+			if err != nil {
+				t.Errorf("Error reading response body: %s", err.Error())
+			}
+
+			var mf = dto.MetricFamily{}
+			if err := proto.Unmarshal(body, &mf); err != nil {
+				t.Errorf("Error unmarshaling response: %s", err.Error())
+			}
+
+			if tc.enableCreatedTimestamps && mf.Metric[0].Counter.CreatedTimestamp == nil {
+				t.Error("expected created timestamp, but there isn't")
+			}
+
+			if !tc.enableCreatedTimestamps && mf.Metric[0].Counter.CreatedTimestamp != nil {
+				t.Error("Did not expected created timestamp, but there is")
+			}
+		})
+	}
+}