expfmt/openmetrics: Write created timestamps for counters, summaries and histograms

Signed-off-by: Arthur Silva Sens <[email protected]>

Author: Arthur Silva Sens

expfmt/openmetrics_create.go

@@ -23,6 +23,7 @@ import (
 	"strings"
 
 	"github.com/prometheus/common/model"
+	"google.golang.org/protobuf/types/known/timestamppb"
 
 	dto "github.com/prometheus/client_model/go"
 )
@@ -152,6 +153,7 @@ func MetricFamilyToOpenMetrics(out io.Writer, in *dto.MetricFamily) (written int
 		return
 	}
 
+	var createdBytesWritten int
 	// Finally the samples, one line for each.
 	for _, metric := range in.Metric {
 		switch metricType {
@@ -169,6 +171,10 @@ func MetricFamilyToOpenMetrics(out io.Writer, in *dto.MetricFamily) (written int
 				metric.Counter.GetValue(), 0, false,
 				metric.Counter.Exemplar,
 			)
+			if metric.Counter.CreatedTimestamp != nil {
+				createdBytesWritten, err = writeOpenMetricsCreated(w, name, "_total", metric, "", 0, metric.Counter.GetCreatedTimestamp())
+				n += createdBytesWritten
+			}
 		case dto.MetricType_GAUGE:
 			if metric.Gauge == nil {
 				return written, fmt.Errorf(
@@ -223,6 +229,10 @@ func MetricFamilyToOpenMetrics(out io.Writer, in *dto.MetricFamily) (written int
 				0, metric.Summary.GetSampleCount(), true,
 				nil,
 			)
+			if metric.Summary.CreatedTimestamp != nil {
+				createdBytesWritten, err = writeOpenMetricsCreated(w, name, "", metric, "", 0, metric.Summary.GetCreatedTimestamp())
+				n += createdBytesWritten
+			}
 		case dto.MetricType_HISTOGRAM:
 			if metric.Histogram == nil {
 				return written, fmt.Errorf(
@@ -271,6 +281,10 @@ func MetricFamilyToOpenMetrics(out io.Writer, in *dto.MetricFamily) (written int
 				0, metric.Histogram.GetSampleCount(), true,
 				nil,
 			)
+			if metric.Histogram.CreatedTimestamp != nil {
+				createdBytesWritten, err = writeOpenMetricsCreated(w, name, "", metric, "", 0, metric.Histogram.GetCreatedTimestamp())
+				n += createdBytesWritten
+			}
 		default:
 			return written, fmt.Errorf(
 				"unexpected type in metric %s %s", name, metric,
@@ -442,6 +456,62 @@ func writeOpenMetricsLabelPairs(
 	return written, nil
 }
 
+// writeOpenMetricsCreated writes the created timestamp for a single time series
+// following OpenMetrics text format to w, given the metric name, the metric proto
+// message itself, optionally a suffix to be removed, e.g. '_total' for counters,
+// an additional label name with a float64 value (use empty string as label name if
+// not required) and the timestamp that represents the created timestamp.
+// The function returns the number of bytes written and any error encountered.
+func writeOpenMetricsCreated(w enhancedWriter,
+	name, suffixToTrim string, metric *dto.Metric,
+	additionalLabelName string, additionalLabelValue float64,
+	createdTimestamp *timestamppb.Timestamp,
+) (int, error) {
+	written := 0
+	n, err := w.WriteString(strings.TrimSuffix(name, suffixToTrim))
+	written += n
+	if err != nil {
+		return written, err
+	}
+
+	n, err = w.WriteString("_created")
+	written += n
+	if err != nil {
+		return written, err
+	}
+
+	n, err = writeOpenMetricsLabelPairs(
+		w, metric.Label, additionalLabelName, additionalLabelValue,
+	)
+	written += n
+	if err != nil {
+		return written, err
+	}
+
+	err = w.WriteByte(' ')
+	written++
+	if err != nil {
+		return written, err
+	}
+
+	ts := createdTimestamp.AsTime()
+	// TODO(beorn7): Format this directly from components of ts to
+	// avoid overflow/underflow and precision issues of the float
+	// conversion.
+	n, err = writeOpenMetricsFloat(w, float64(ts.UnixNano())/1e9)
+	written += n
+	if err != nil {
+		return written, err
+	}
+
+	err = w.WriteByte('\n')
+	written++
+	if err != nil {
+		return written, err
+	}
+	return written, nil
+}
+
 // writeExemplar writes the provided exemplar in OpenMetrics format to w. The
 // function returns the number of bytes written and any error encountered.
 func writeExemplar(w enhancedWriter, e *dto.Exemplar) (int, error) {