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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package main
import (
"context"
"fmt"
"log"
"math/rand"
"net/http"
"os"
"os/signal"
"time"
"github.com/prometheus/client_golang/prometheus/promhttp"
"go.opentelemetry.io/otel/attribute"
"go.opentelemetry.io/otel/exporters/prometheus"
api "go.opentelemetry.io/otel/metric"
"go.opentelemetry.io/otel/sdk/metric"
)
const meterName = "go.opentelemetry.io/contrib/examples/prometheus"
func main() {
rng := rand.New(rand.NewSource(time.Now().UnixNano())) //nolint:gosec // G404: Use of weak random number generator (math/rand instead of crypto/rand) is ignored as this is not security-sensitive.
ctx := context.Background()
// The exporter embeds a default OpenTelemetry Reader and
// implements prometheus.Collector, allowing it to be used as
// both a Reader and Collector.
exporter, err := prometheus.New()
if err != nil {
log.Fatal(err)
}
provider := metric.NewMeterProvider(metric.WithReader(exporter))
meter := provider.Meter(meterName)
// Start the prometheus HTTP server and pass the exporter Collector to it
go serveMetrics()
opt := api.WithAttributes(
attribute.Key("A").String("B"),
attribute.Key("C").String("D"),
)
// This is the equivalent of prometheus.NewCounterVec
counter, err := meter.Float64Counter("foo", api.WithDescription("a simple counter"))
if err != nil {
log.Fatal(err)
}
counter.Add(ctx, 5, opt)
gauge, err := meter.Float64ObservableGauge("bar", api.WithDescription("a fun little gauge"))
if err != nil {
log.Fatal(err)
}
_, err = meter.RegisterCallback(func(_ context.Context, o api.Observer) error {
n := -10. + rng.Float64()*(90.) // [-10, 100)
o.ObserveFloat64(gauge, n, opt)
return nil
}, gauge)
if err != nil {
log.Fatal(err)
}
// This is the equivalent of prometheus.NewHistogramVec
histogram, err := meter.Float64Histogram(
"baz",
api.WithDescription("a histogram with custom buckets and rename"),
api.WithExplicitBucketBoundaries(64, 128, 256, 512, 1024, 2048, 4096),
)
if err != nil {
log.Fatal(err)
}
histogram.Record(ctx, 136, opt)
histogram.Record(ctx, 64, opt)
histogram.Record(ctx, 701, opt)
histogram.Record(ctx, 830, opt)
ctx, _ = signal.NotifyContext(ctx, os.Interrupt)
<-ctx.Done()
}
func serveMetrics() {
log.Printf("serving metrics at localhost:2223/metrics")
http.Handle("/metrics", promhttp.Handler())
err := http.ListenAndServe(":2223", nil) //nolint:gosec // Ignoring G114: Use of net/http serve function that has no support for setting timeouts.
if err != nil {
fmt.Printf("error serving http: %v", err)
return
}
}
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