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528 lines
13 KiB
Go
528 lines
13 KiB
Go
// Copyright 2020 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package expfmt
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import (
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"bufio"
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"bytes"
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"fmt"
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"io"
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"math"
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"strconv"
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"strings"
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"github.com/prometheus/common/model"
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dto "github.com/prometheus/client_model/go"
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)
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// MetricFamilyToOpenMetrics converts a MetricFamily proto message into the
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// OpenMetrics text format and writes the resulting lines to 'out'. It returns
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// the number of bytes written and any error encountered. The output will have
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// the same order as the input, no further sorting is performed. Furthermore,
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// this function assumes the input is already sanitized and does not perform any
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// sanity checks. If the input contains duplicate metrics or invalid metric or
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// label names, the conversion will result in invalid text format output.
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//
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// This function fulfills the type 'expfmt.encoder'.
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//
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// Note that OpenMetrics requires a final `# EOF` line. Since this function acts
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// on individual metric families, it is the responsibility of the caller to
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// append this line to 'out' once all metric families have been written.
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// Conveniently, this can be done by calling FinalizeOpenMetrics.
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//
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// The output should be fully OpenMetrics compliant. However, there are a few
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// missing features and peculiarities to avoid complications when switching from
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// Prometheus to OpenMetrics or vice versa:
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//
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// - Counters are expected to have the `_total` suffix in their metric name. In
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// the output, the suffix will be truncated from the `# TYPE` and `# HELP`
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// line. A counter with a missing `_total` suffix is not an error. However,
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// its type will be set to `unknown` in that case to avoid invalid OpenMetrics
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// output.
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//
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// - No support for the following (optional) features: `# UNIT` line, `_created`
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// line, info type, stateset type, gaugehistogram type.
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//
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// - The size of exemplar labels is not checked (i.e. it's possible to create
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// exemplars that are larger than allowed by the OpenMetrics specification).
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//
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// - The value of Counters is not checked. (OpenMetrics doesn't allow counters
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// with a `NaN` value.)
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func MetricFamilyToOpenMetrics(out io.Writer, in *dto.MetricFamily) (written int, err error) {
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name := in.GetName()
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if name == "" {
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return 0, fmt.Errorf("MetricFamily has no name: %s", in)
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}
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// Try the interface upgrade. If it doesn't work, we'll use a
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// bufio.Writer from the sync.Pool.
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w, ok := out.(enhancedWriter)
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if !ok {
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b := bufPool.Get().(*bufio.Writer)
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b.Reset(out)
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w = b
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defer func() {
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bErr := b.Flush()
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if err == nil {
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err = bErr
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}
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bufPool.Put(b)
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}()
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}
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var (
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n int
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metricType = in.GetType()
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shortName = name
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)
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if metricType == dto.MetricType_COUNTER && strings.HasSuffix(shortName, "_total") {
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shortName = name[:len(name)-6]
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}
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// Comments, first HELP, then TYPE.
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if in.Help != nil {
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n, err = w.WriteString("# HELP ")
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written += n
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if err != nil {
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return
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}
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n, err = w.WriteString(shortName)
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written += n
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if err != nil {
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return
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}
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err = w.WriteByte(' ')
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written++
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if err != nil {
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return
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}
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n, err = writeEscapedString(w, *in.Help, true)
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written += n
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if err != nil {
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return
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}
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err = w.WriteByte('\n')
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written++
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if err != nil {
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return
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}
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}
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n, err = w.WriteString("# TYPE ")
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written += n
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if err != nil {
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return
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}
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n, err = w.WriteString(shortName)
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written += n
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if err != nil {
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return
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}
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switch metricType {
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case dto.MetricType_COUNTER:
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if strings.HasSuffix(name, "_total") {
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n, err = w.WriteString(" counter\n")
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} else {
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n, err = w.WriteString(" unknown\n")
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}
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case dto.MetricType_GAUGE:
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n, err = w.WriteString(" gauge\n")
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case dto.MetricType_SUMMARY:
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n, err = w.WriteString(" summary\n")
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case dto.MetricType_UNTYPED:
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n, err = w.WriteString(" unknown\n")
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case dto.MetricType_HISTOGRAM:
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n, err = w.WriteString(" histogram\n")
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default:
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return written, fmt.Errorf("unknown metric type %s", metricType.String())
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}
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written += n
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if err != nil {
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return
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}
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// Finally the samples, one line for each.
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for _, metric := range in.Metric {
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switch metricType {
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case dto.MetricType_COUNTER:
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if metric.Counter == nil {
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return written, fmt.Errorf(
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"expected counter in metric %s %s", name, metric,
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)
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}
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// Note that we have ensured above that either the name
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// ends on `_total` or that the rendered type is
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// `unknown`. Therefore, no `_total` must be added here.
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n, err = writeOpenMetricsSample(
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w, name, "", metric, "", 0,
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metric.Counter.GetValue(), 0, false,
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metric.Counter.Exemplar,
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)
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case dto.MetricType_GAUGE:
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if metric.Gauge == nil {
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return written, fmt.Errorf(
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"expected gauge in metric %s %s", name, metric,
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)
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}
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n, err = writeOpenMetricsSample(
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w, name, "", metric, "", 0,
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metric.Gauge.GetValue(), 0, false,
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nil,
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)
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case dto.MetricType_UNTYPED:
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if metric.Untyped == nil {
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return written, fmt.Errorf(
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"expected untyped in metric %s %s", name, metric,
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)
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}
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n, err = writeOpenMetricsSample(
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w, name, "", metric, "", 0,
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metric.Untyped.GetValue(), 0, false,
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nil,
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)
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case dto.MetricType_SUMMARY:
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if metric.Summary == nil {
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return written, fmt.Errorf(
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"expected summary in metric %s %s", name, metric,
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)
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}
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for _, q := range metric.Summary.Quantile {
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n, err = writeOpenMetricsSample(
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w, name, "", metric,
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model.QuantileLabel, q.GetQuantile(),
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q.GetValue(), 0, false,
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nil,
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)
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written += n
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if err != nil {
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return
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}
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}
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n, err = writeOpenMetricsSample(
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w, name, "_sum", metric, "", 0,
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metric.Summary.GetSampleSum(), 0, false,
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nil,
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)
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written += n
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if err != nil {
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return
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}
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n, err = writeOpenMetricsSample(
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w, name, "_count", metric, "", 0,
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0, metric.Summary.GetSampleCount(), true,
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nil,
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)
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case dto.MetricType_HISTOGRAM:
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if metric.Histogram == nil {
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return written, fmt.Errorf(
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"expected histogram in metric %s %s", name, metric,
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)
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}
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infSeen := false
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for _, b := range metric.Histogram.Bucket {
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n, err = writeOpenMetricsSample(
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w, name, "_bucket", metric,
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model.BucketLabel, b.GetUpperBound(),
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0, b.GetCumulativeCount(), true,
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b.Exemplar,
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)
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written += n
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if err != nil {
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return
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}
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if math.IsInf(b.GetUpperBound(), +1) {
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infSeen = true
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}
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}
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if !infSeen {
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n, err = writeOpenMetricsSample(
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w, name, "_bucket", metric,
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model.BucketLabel, math.Inf(+1),
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0, metric.Histogram.GetSampleCount(), true,
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nil,
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)
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written += n
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if err != nil {
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return
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}
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}
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n, err = writeOpenMetricsSample(
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w, name, "_sum", metric, "", 0,
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metric.Histogram.GetSampleSum(), 0, false,
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nil,
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)
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written += n
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if err != nil {
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return
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}
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n, err = writeOpenMetricsSample(
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w, name, "_count", metric, "", 0,
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0, metric.Histogram.GetSampleCount(), true,
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nil,
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)
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default:
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return written, fmt.Errorf(
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"unexpected type in metric %s %s", name, metric,
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)
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}
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written += n
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if err != nil {
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return
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}
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}
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return
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}
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// FinalizeOpenMetrics writes the final `# EOF\n` line required by OpenMetrics.
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func FinalizeOpenMetrics(w io.Writer) (written int, err error) {
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return w.Write([]byte("# EOF\n"))
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}
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// writeOpenMetricsSample writes a single sample in OpenMetrics text format to
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// w, given the metric name, the metric proto message itself, optionally an
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// additional label name with a float64 value (use empty string as label name if
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// not required), the value (optionally as float64 or uint64, determined by
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// useIntValue), and optionally an exemplar (use nil if not required). The
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// function returns the number of bytes written and any error encountered.
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func writeOpenMetricsSample(
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w enhancedWriter,
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name, suffix string,
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metric *dto.Metric,
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additionalLabelName string, additionalLabelValue float64,
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floatValue float64, intValue uint64, useIntValue bool,
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exemplar *dto.Exemplar,
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) (int, error) {
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var written int
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n, err := w.WriteString(name)
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written += n
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if err != nil {
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return written, err
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}
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if suffix != "" {
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n, err = w.WriteString(suffix)
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written += n
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if err != nil {
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return written, err
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}
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}
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n, err = writeOpenMetricsLabelPairs(
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w, metric.Label, additionalLabelName, additionalLabelValue,
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)
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written += n
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if err != nil {
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return written, err
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}
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err = w.WriteByte(' ')
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written++
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if err != nil {
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return written, err
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}
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if useIntValue {
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n, err = writeUint(w, intValue)
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} else {
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n, err = writeOpenMetricsFloat(w, floatValue)
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}
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written += n
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if err != nil {
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return written, err
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}
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if metric.TimestampMs != nil {
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err = w.WriteByte(' ')
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written++
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if err != nil {
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return written, err
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}
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// TODO(beorn7): Format this directly without converting to a float first.
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n, err = writeOpenMetricsFloat(w, float64(*metric.TimestampMs)/1000)
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written += n
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if err != nil {
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return written, err
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}
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}
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if exemplar != nil {
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n, err = writeExemplar(w, exemplar)
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written += n
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if err != nil {
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return written, err
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}
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}
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err = w.WriteByte('\n')
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written++
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if err != nil {
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return written, err
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}
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return written, nil
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}
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// writeOpenMetricsLabelPairs works like writeOpenMetrics but formats the float
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// in OpenMetrics style.
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func writeOpenMetricsLabelPairs(
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w enhancedWriter,
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in []*dto.LabelPair,
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additionalLabelName string, additionalLabelValue float64,
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) (int, error) {
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if len(in) == 0 && additionalLabelName == "" {
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return 0, nil
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}
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var (
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written int
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separator byte = '{'
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)
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for _, lp := range in {
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err := w.WriteByte(separator)
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written++
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if err != nil {
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return written, err
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}
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n, err := w.WriteString(lp.GetName())
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written += n
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if err != nil {
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return written, err
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}
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n, err = w.WriteString(`="`)
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written += n
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if err != nil {
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return written, err
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}
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n, err = writeEscapedString(w, lp.GetValue(), true)
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written += n
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if err != nil {
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return written, err
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}
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err = w.WriteByte('"')
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written++
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if err != nil {
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return written, err
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}
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separator = ','
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}
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if additionalLabelName != "" {
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err := w.WriteByte(separator)
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written++
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if err != nil {
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return written, err
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}
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n, err := w.WriteString(additionalLabelName)
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written += n
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if err != nil {
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return written, err
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}
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n, err = w.WriteString(`="`)
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written += n
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if err != nil {
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return written, err
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}
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n, err = writeOpenMetricsFloat(w, additionalLabelValue)
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written += n
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if err != nil {
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return written, err
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}
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err = w.WriteByte('"')
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written++
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if err != nil {
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return written, err
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}
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}
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err := w.WriteByte('}')
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written++
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if err != nil {
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return written, err
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}
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return written, nil
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}
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// writeExemplar writes the provided exemplar in OpenMetrics format to w. The
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// function returns the number of bytes written and any error encountered.
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func writeExemplar(w enhancedWriter, e *dto.Exemplar) (int, error) {
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written := 0
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n, err := w.WriteString(" # ")
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written += n
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if err != nil {
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return written, err
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}
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n, err = writeOpenMetricsLabelPairs(w, e.Label, "", 0)
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written += n
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if err != nil {
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return written, err
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}
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err = w.WriteByte(' ')
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written++
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if err != nil {
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return written, err
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}
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n, err = writeOpenMetricsFloat(w, e.GetValue())
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written += n
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if err != nil {
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return written, err
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}
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if e.Timestamp != nil {
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err = w.WriteByte(' ')
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written++
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if err != nil {
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return written, err
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}
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err = (*e).Timestamp.CheckValid()
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if err != nil {
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return written, err
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}
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ts := (*e).Timestamp.AsTime()
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// TODO(beorn7): Format this directly from components of ts to
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// avoid overflow/underflow and precision issues of the float
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// conversion.
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n, err = writeOpenMetricsFloat(w, float64(ts.UnixNano())/1e9)
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written += n
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if err != nil {
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return written, err
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}
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}
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return written, nil
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}
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// writeOpenMetricsFloat works like writeFloat but appends ".0" if the resulting
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// number would otherwise contain neither a "." nor an "e".
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func writeOpenMetricsFloat(w enhancedWriter, f float64) (int, error) {
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switch {
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case f == 1:
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return w.WriteString("1.0")
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case f == 0:
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return w.WriteString("0.0")
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case f == -1:
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return w.WriteString("-1.0")
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case math.IsNaN(f):
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return w.WriteString("NaN")
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case math.IsInf(f, +1):
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return w.WriteString("+Inf")
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case math.IsInf(f, -1):
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return w.WriteString("-Inf")
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default:
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bp := numBufPool.Get().(*[]byte)
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*bp = strconv.AppendFloat((*bp)[:0], f, 'g', -1, 64)
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if !bytes.ContainsAny(*bp, "e.") {
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*bp = append(*bp, '.', '0')
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}
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written, err := w.Write(*bp)
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numBufPool.Put(bp)
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return written, err
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}
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}
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// writeUint is like writeInt just for uint64.
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func writeUint(w enhancedWriter, u uint64) (int, error) {
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bp := numBufPool.Get().(*[]byte)
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*bp = strconv.AppendUint((*bp)[:0], u, 10)
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written, err := w.Write(*bp)
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numBufPool.Put(bp)
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return written, err
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}
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