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exporter.go
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exporter.go
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// Copyright The OpenTelemetry 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 prometheus // import "go.opentelemetry.io/otel/exporters/prometheus"
import (
"context"
"fmt"
"sort"
"strings"
"unicode"
"unicode/utf8"
"github.com/prometheus/client_golang/prometheus"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/attribute"
"go.opentelemetry.io/otel/sdk/metric"
"go.opentelemetry.io/otel/sdk/metric/metricdata"
)
// Exporter is a Prometheus Exporter that embeds the OTel metric.Reader
// interface for easy instantiation with a MeterProvider.
type Exporter struct {
metric.Reader
}
var _ metric.Reader = &Exporter{}
// collector is used to implement prometheus.Collector.
type collector struct {
reader metric.Reader
}
// New returns a Prometheus Exporter.
func New(opts ...Option) (*Exporter, error) {
cfg := newConfig(opts...)
// this assumes that the default temporality selector will always return cumulative.
// we only support cumulative temporality, so building our own reader enforces this.
// TODO (#3244): Enable some way to configure the reader, but not change temporality.
reader := metric.NewManualReader()
collector := &collector{
reader: reader,
}
if err := cfg.registerer.Register(collector); err != nil {
return nil, fmt.Errorf("cannot register the collector: %w", err)
}
e := &Exporter{
Reader: reader,
}
return e, nil
}
// Describe implements prometheus.Collector.
func (c *collector) Describe(ch chan<- *prometheus.Desc) {
}
// Collect implements prometheus.Collector.
func (c *collector) Collect(ch chan<- prometheus.Metric) {
metrics, err := c.reader.Collect(context.TODO())
if err != nil {
otel.Handle(err)
}
// TODO(#3166): convert otel resource to target_info
// see https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/data-model.md#resource-attributes-1
for _, scopeMetrics := range metrics.ScopeMetrics {
for _, m := range scopeMetrics.Metrics {
switch v := m.Data.(type) {
case metricdata.Histogram:
addHistogramMetric(ch, v, m)
case metricdata.Sum[int64]:
addSumMetric(ch, v, m)
case metricdata.Sum[float64]:
addSumMetric(ch, v, m)
case metricdata.Gauge[int64]:
addGaugeMetric(ch, v, m)
case metricdata.Gauge[float64]:
addGaugeMetric(ch, v, m)
}
}
}
}
func addHistogramMetric(ch chan<- prometheus.Metric, histogram metricdata.Histogram, m metricdata.Metrics) {
// TODO(https://github.com/open-telemetry/opentelemetry-go/issues/3163): support exemplars
for _, dp := range histogram.DataPoints {
keys, values := getAttrs(dp.Attributes)
desc := prometheus.NewDesc(sanitizeName(m.Name), m.Description, keys, nil)
buckets := make(map[float64]uint64, len(dp.Bounds))
cumulativeCount := uint64(0)
for i, bound := range dp.Bounds {
cumulativeCount += dp.BucketCounts[i]
buckets[bound] = cumulativeCount
}
m, err := prometheus.NewConstHistogram(desc, dp.Count, dp.Sum, buckets, values...)
if err != nil {
otel.Handle(err)
continue
}
ch <- m
}
}
func addSumMetric[N int64 | float64](ch chan<- prometheus.Metric, sum metricdata.Sum[N], m metricdata.Metrics) {
for _, dp := range sum.DataPoints {
keys, values := getAttrs(dp.Attributes)
desc := prometheus.NewDesc(sanitizeName(m.Name), m.Description, keys, nil)
m, err := prometheus.NewConstMetric(desc, prometheus.CounterValue, float64(dp.Value), values...)
if err != nil {
otel.Handle(err)
continue
}
ch <- m
}
}
func addGaugeMetric[N int64 | float64](ch chan<- prometheus.Metric, gauge metricdata.Gauge[N], m metricdata.Metrics) {
for _, dp := range gauge.DataPoints {
keys, values := getAttrs(dp.Attributes)
desc := prometheus.NewDesc(sanitizeName(m.Name), m.Description, keys, nil)
m, err := prometheus.NewConstMetric(desc, prometheus.GaugeValue, float64(dp.Value), values...)
if err != nil {
otel.Handle(err)
continue
}
ch <- m
}
}
// getAttrs parses the attribute.Set to two lists of matching Prometheus-style
// keys and values. It sanitizes invalid characters and handles duplicate keys
// (due to sanitization) by sorting and concatenating the values following the spec.
func getAttrs(attrs attribute.Set) ([]string, []string) {
keysMap := make(map[string][]string)
itr := attrs.Iter()
for itr.Next() {
kv := itr.Attribute()
key := strings.Map(sanitizeRune, string(kv.Key))
if _, ok := keysMap[key]; !ok {
keysMap[key] = []string{kv.Value.Emit()}
} else {
// if the sanitized key is a duplicate, append to the list of keys
keysMap[key] = append(keysMap[key], kv.Value.Emit())
}
}
keys := make([]string, 0, attrs.Len())
values := make([]string, 0, attrs.Len())
for key, vals := range keysMap {
keys = append(keys, key)
sort.Slice(vals, func(i, j int) bool {
return i < j
})
values = append(values, strings.Join(vals, ";"))
}
return keys, values
}
func sanitizeRune(r rune) rune {
if unicode.IsLetter(r) || unicode.IsDigit(r) || r == ':' || r == '_' {
return r
}
return '_'
}
func sanitizeName(n string) string {
// This algorithm is based on strings.Map from Go 1.19.
const replacement = '_'
valid := func(i int, r rune) bool {
// Taken from
// https://github.com/prometheus/common/blob/dfbc25bd00225c70aca0d94c3c4bb7744f28ace0/model/metric.go#L92-L102
if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || r == '_' || r == ':' || (r >= '0' && r <= '9' && i > 0) {
return true
}
return false
}
// This output buffer b is initialized on demand, the first time a
// character needs to be replaced.
var b strings.Builder
for i, c := range n {
if valid(i, c) {
continue
}
if i == 0 && c >= '0' && c <= '9' {
// Prefix leading number with replacement character.
b.Grow(len(n) + 1)
b.WriteByte(byte(replacement))
break
}
b.Grow(len(n))
b.WriteString(n[:i])
b.WriteByte(byte(replacement))
width := utf8.RuneLen(c)
n = n[i+width:]
break
}
// Fast path for unchanged input.
if b.Cap() == 0 { // b.Grow was not called above.
return n
}
for _, c := range n {
// Due to inlining, it is more performant to invoke WriteByte rather then
// WriteRune.
if valid(1, c) { // We are guaranteed to not be at the start.
b.WriteByte(byte(c))
} else {
b.WriteByte(byte(replacement))
}
}
return b.String()
}