// MetricFamilyToText converts a MetricFamily proto message into text format and
// writes the resulting lines to 'out'. It returns the number of bytes written
// and any error encountered. This function does not perform checks on the
// content of the metric and label names, i.e. invalid metric or label names
// will result in invalid text format output.
// This method fulfills the type 'prometheus.encoder'.
func MetricFamilyToText(out io.Writer, in *dto.MetricFamily) (int, error) {
var written int
// Fail-fast checks.
if len(in.Metric) == 0 {
return written, fmt.Errorf("MetricFamily has no metrics: %s", in)
}
name := in.GetName()
if name == "" {
return written, fmt.Errorf("MetricFamily has no name: %s", in)
}
if in.Type == nil {
return written, fmt.Errorf("MetricFamily has no type: %s", in)
}
// Comments, first HELP, then TYPE.
if in.Help != nil {
n, err := fmt.Fprintf(
out, "# HELP %s %s\n",
name, escapeString(*in.Help, false),
)
written += n
if err != nil {
return written, err
}
}
metricType := in.GetType()
n, err := fmt.Fprintf(
out, "# TYPE %s %s\n",
name, strings.ToLower(metricType.String()),
)
written += n
if err != nil {
return written, err
}
// Finally the samples, one line for each.
for _, metric := range in.Metric {
switch metricType {
case dto.MetricType_COUNTER:
if metric.Counter == nil {
return written, fmt.Errorf(
"expected counter in metric %s", metric,
)
}
n, err = writeSample(
name, metric, "", "",
metric.Counter.GetValue(),
out,
)
case dto.MetricType_GAUGE:
if metric.Gauge == nil {
return written, fmt.Errorf(
"expected gauge in metric %s", metric,
)
}
n, err = writeSample(
name, metric, "", "",
metric.Gauge.GetValue(),
out,
)
case dto.MetricType_UNTYPED:
if metric.Untyped == nil {
return written, fmt.Errorf(
"expected untyped in metric %s", metric,
)
}
n, err = writeSample(
name, metric, "", "",
metric.Untyped.GetValue(),
out,
)
case dto.MetricType_SUMMARY:
if metric.Summary == nil {
return written, fmt.Errorf(
"expected summary in metric %s", metric,
)
}
for _, q := range metric.Summary.Quantile {
n, err = writeSample(
name, metric,
"quantile", fmt.Sprint(q.GetQuantile()),
q.GetValue(),
out,
)
written += n
if err != nil {
return written, err
}
}
n, err = writeSample(
name+"_sum", metric, "", "",
metric.Summary.GetSampleSum(),
out,
)
if err != nil {
return written, err
}
written += n
n, err = writeSample(
name+"_count", metric, "", "",
float64(metric.Summary.GetSampleCount()),
out,
)
case dto.MetricType_HISTOGRAM:
if metric.Histogram == nil {
return written, fmt.Errorf(
"expected summary in metric %s", metric,
)
}
for _, q := range metric.Histogram.Bucket {
n, err = writeSample(
name+"_bucket", metric,
"le", fmt.Sprint(q.GetUpperBound()),
float64(q.GetCumulativeCount()),
out,
)
written += n
if err != nil {
return written, err
}
// TODO: Add +inf bucket if it's missing.
}
n, err = writeSample(
name+"_sum", metric, "", "",
metric.Histogram.GetSampleSum(),
out,
)
if err != nil {
return written, err
}
written += n
n, err = writeSample(
name+"_count", metric, "", "",
float64(metric.Histogram.GetSampleCount()),
out,
)
default:
return written, fmt.Errorf(
"unexpected type in metric %s", metric,
)
}
written += n
if err != nil {
return written, err
}
}
return written, nil
}
