client_golang/text/create.go

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// Copyright 2014 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package text contains helper functions to parse and create text-based
// exchange formats. The package currently supports (only) version 0.0.4 of the
// exchange format. Should other versions be supported in the future, some
// versioning scheme has to be applied. Possibilities include separate packages
// or separate functions. The best way depends on the nature of future changes,
// which is the reason why no versioning scheme has been applied prematurely
// here.
package text
import (
"bytes"
"fmt"
"io"
"strings"
dto "github.com/prometheus/client_model/go"
)
// 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,
)
default:
return written, fmt.Errorf(
"unexpected type in metric %s", metric,
)
}
written += n
if err != nil {
return written, err
}
}
return written, nil
}
// writeSample writes a single sample in text format to out, given the metric
// name, the metric proto message itself, optionally an additional label name
// and value (use empty strings if not required), and the value. The function
// returns the number of bytes written and any error encountered.
func writeSample(
name string,
metric *dto.Metric,
additionalLabelName, additionalLabelValue string,
value float64,
out io.Writer,
) (int, error) {
var written int
n, err := fmt.Fprint(out, name)
written += n
if err != nil {
return written, err
}
n, err = labelPairsToText(
metric.Label,
additionalLabelName, additionalLabelValue,
out,
)
written += n
if err != nil {
return written, err
}
n, err = fmt.Fprintf(out, " %v", value)
written += n
if err != nil {
return written, err
}
if metric.TimestampMs != nil {
n, err = fmt.Fprintf(out, " %v", *metric.TimestampMs)
written += n
if err != nil {
return written, err
}
}
n, err = out.Write([]byte{'\n'})
written += n
if err != nil {
return written, err
}
return written, nil
}
// labelPairsToText converts a slice of LabelPair proto messages plus the
// explicitly given additional label pair into text formatted as required by the
// text format and writes it to 'out'. An empty slice in combination with an
// empty string 'additionalLabelName' results in nothing being
// written. Otherwise, the label pairs are written, escaped as required by the
// text format, and enclosed in '{...}'. The function returns the number of
// bytes written and any error encountered.
func labelPairsToText(
in []*dto.LabelPair,
additionalLabelName, additionalLabelValue string,
out io.Writer,
) (int, error) {
if len(in) == 0 && additionalLabelName == "" {
return 0, nil
}
var written int
separator := '{'
for _, lp := range in {
n, err := fmt.Fprintf(
out, `%c%s="%s"`,
separator, lp.GetName(), escapeString(lp.GetValue(), true),
)
written += n
if err != nil {
return written, err
}
separator = ','
}
if additionalLabelName != "" {
n, err := fmt.Fprintf(
out, `%c%s="%s"`,
separator, additionalLabelName,
escapeString(additionalLabelValue, true),
)
written += n
if err != nil {
return written, err
}
}
n, err := out.Write([]byte{'}'})
written += n
if err != nil {
return written, err
}
return written, nil
}
// escapeString replaces '\' by '\\', new line character by '\n', and - if
// includeDoubleQuote is true - '"' by '\"'.
func escapeString(v string, includeDoubleQuote bool) string {
result := bytes.NewBuffer(make([]byte, 0, len(v)))
for _, c := range v {
switch {
case c == '\\':
result.WriteString(`\\`)
case includeDoubleQuote && c == '"':
result.WriteString(`\"`)
case c == '\n':
result.WriteString(`\n`)
default:
result.WriteRune(c)
}
}
return result.String()
}