Prometheus: receiving and exporting metrics
You can use OpenTelemetry Collector to collect Prometheus metrics using Prometheus receiver and export OpenTelemetry metrics to Prometheus using Promethes exporter.
What is OpenTelemetry?
OpenTelemetry is an open source and vendor-neutral API for distributed tracing (including logs and errors) and OpenTelemetry metrics. With OpenTelemetry, you can instrument your application once and then add or change OpenTelemetry-compatible backends without changing the instrumentation.
What is OpenTelemetry Collector?
OpenTelemetry Collector is a proxy between your application and a backend that receives telemetry data, transforms it, and exports the data to various observability platforms, storage systems, or other destinations.
Collector can also act as an agent that pulls telemetry data from monitored systems, for example, Redis or filesystem metrics.
Prometheus receiver
You can use OpenTelemetry Collector to pull Prometheus metrics using Prometheus receiver:
When collecting metrics from Prometheus, OpenTelemetry Collector acts as a Prometheus server itself, scraping metrics from one or more Prometheus exporters, and then processing and exporting the collected metrics to configured destinations, for example, Uptrace APM.
receivers:
prometheus_simple:
collection_interval: 10s
endpoint: '172.17.0.5:9153'
metrics_path: '/metrics'
use_service_account: false
tls:
ca_file: '/path/to/ca'
cert_file: '/path/to/cert'
key_file: '/path/to/key'
insecure_skip_verify: true
exporters:
otlp/uptrace:
endpoint: otlp.uptrace.dev:4317
headers:
# Copy your project DSN here
uptrace-dsn: 'https://<token>@uptrace.dev/<project_id>'
service:
pipelines:
metrics:
receivers: [prometheus_simple]
exporters: [otlp/uptrace]
Prometheus exporter
OpenTelemetry Collector Prometheus Exporter is a component that allows users to export metrics from the OpenTelemetry Collector to the Prometheus monitoring system.
To use the OpenTelemetry Collector Prometheus Exporter, you need to configure it with the desired configuration parameters.
The exporter allows you to add custom labels and metadata to the exported metrics, which can be useful for organizing and categorizing metrics in Prometheus.
exporters:
prometheus:
endpoint: '1.2.3.4:1234'
namespace: test-space
const_labels:
label1: value1
'another label': spaced value
send_timestamps: true
metric_expiration: 180m
resource_to_telemetry_conversion:
enabled: true
service:
pipelines:
metrics:
receivers: [otlp]
exporters: [prometheus]
Once the exporter is configured and enabled, it will collect metrics from the OpenTelemetry Collector and forward them to the specified Prometheus server. Users can then use Prometheus tools to query, visualize, and alert on the collected metrics.
Sending metrics from Go to Prometheus
OpenTelemetry specifies how to collect, aggregate, and send metrics to backend platforms. Using OpenTelemetry instruments, you can create counter, gauge, and histogram metrics.
The simplest Counter instrument looks like this:
import "go.opentelemetry.io/otel/metric/instrument"
counter := Meter.SyncInt64().Counter(
"test.my_counter",
instrument.WithUnit("1"),
instrument.WithDescription("Just a test counter"),
)
// Increment the counter.
counter.Add(ctx, 1, attribute.String("foo", "bar"))
counter.Add(ctx, 10, attribute.String("hello", "world"))
To send OpenTelemetry Go metrics to Prometheus, you need to provide a Prometheus target:
import (
"go.opentelemetry.io/otel/exporters/prometheus"
"go.opentelemetry.io/otel/metric/global"
"go.opentelemetry.io/otel/sdk/export/metric/aggregation"
"go.opentelemetry.io/otel/sdk/metric/aggregator/histogram"
controller "go.opentelemetry.io/otel/sdk/metric/controller/basic"
processor "go.opentelemetry.io/otel/sdk/metric/processor/basic"
selector "go.opentelemetry.io/otel/sdk/metric/selector/simple"
)
func configureOpentelemetry() {
exporter := configureMetrics()
http.HandleFunc("/metrics", exporter.ServeHTTP)
fmt.Println("listenening on http://localhost:8088/metrics")
go func() {
_ = http.ListenAndServe(":8088", nil)
}()
}
func configureMetrics() *prometheus.Exporter {
config := prometheus.Config{}
ctrl := controller.New(
processor.NewFactory(
selector.NewWithHistogramDistribution(
histogram.WithExplicitBoundaries(config.DefaultHistogramBoundaries),
),
export.CumulativeExportKindSelector(),
processor.WithMemory(true),
),
)
exporter, err := prometheus.New(config, ctrl)
if err != nil {
panic(err)
}
global.SetMeterProvider(exporter.MeterProvider())
return exporter
}
And then configure Prometheus to scrape exposed metrics:
scrape_configs:
- job_name: 'opentelemetry'
static_configs:
- targets: ['localhost:8088']
You can find a runnable example at GitHub.
See also
