OpenTelemetry.Exporter.Prometheus.HttpListener 1.17.0-beta.1

Prometheus Exporter HttpListener for OpenTelemetry .NET

An OpenTelemetry Prometheus exporter that configures an HttpListener instance for Prometheus to scrape.

Prerequisite

• Get Prometheus

Installation

Step 1: Install Package

dotnet add package --prerelease OpenTelemetry.Exporter.Prometheus.HttpListener

Step 2: Add PrometheusHttpListener

var meterProvider = Sdk.CreateMeterProviderBuilder()
    .AddMeter(MyMeter.Name)
    .AddPrometheusHttpListener()
    .Build();

Configuration

You can configure the PrometheusHttpListener through PrometheusHttpListenerOptions and environment variables. The PrometheusHttpListenerOptions setters take precedence over the environment variables.

Configuration using Properties

• Host: The host used by the Prometheus exporter (default localhost).
• Port: The port used by the Prometheus exporter (default 9464).
• ScopeInfoEnabled: Whether to include scope labels in metrics (default true).
• ScrapeEndpointPath: Defines the Prometheus scrape endpoint path. (default "/metrics").
• TargetInfoEnabled: Whether to produce a target_info metric (default true).
• ResourceConstantLabels: A predicate selecting which resource attributes are added to each metric as constant labels (default null).
• DisableTotalNameSuffixForCounters: Whether to disable the _total suffix for counter metrics (default false).
• TranslationStrategy: Controls how OpenTelemetry metric and label names are translated into Prometheus names (default UnderscoreEscapingWithSuffixes). See TranslationStrategy below.
• DisableTimestamp: Whether to disable the timestamp for metrics (default false).
• ConfigureHttpListener: A delegate that can be used to apply custom configuration to the HttpListener instance used by the exporter before use.

Configuration using Dependency Injection

This exporter allows easy configuration of PrometheusHttpListenerOptions from the dependency injection container, when used in conjunction with OpenTelemetry.Extensions.Hosting.

For example:

var meterProvider = Sdk.CreateMeterProviderBuilder()
    .AddMeter(MyMeter.Name)
    .AddPrometheusHttpListener(options =>
    {
        options.Host = "localhost";
        options.Port = 9464;
    })
    .Build();

Configuration using Environment Variables

The following environment variables can be used to override the default values of the PrometheusHttpListenerOptions.

ScopeInfoEnabled

Specifies whether metrics include scope labels. Default value: true. Set to false to disable scope labels.

ScrapeResponseCacheDurationMilliseconds

Configures scrape endpoint response caching. Multiple scrape requests within the cache duration time period will receive the same previously generated response. The default value is 300. Set to 0 to disable response caching.

TargetInfoEnabled

Specifies whether to produce a target_info metric. Default value: true. Set to false to disable the target_info metric.

ResourceConstantLabels

A predicate used to select which resource attributes are added to each metric as constant labels. The predicate is invoked with the resource attribute key and should return true to include the attribute. Default value: null (no resource attributes are added as metric labels). Resource attributes copied as metric labels are always included in the target_info metric regardless of this predicate.

var meterProvider = Sdk.CreateMeterProviderBuilder()
    .AddMeter(MyMeter.Name)
    .AddPrometheusHttpListener(options =>
    {
        // Add all resource attributes as metric labels.
        options.ResourceConstantLabels = static _ => true;
    })
    .Build();

TranslationStrategy

Controls how OpenTelemetry metric and label names are translated into Prometheus names, following the OpenTelemetry specification's translation_strategy option. The strategy combines two independent choices: whether discouraged characters are escaped to _ or UTF-8 names are passed through unaltered, and whether unit and type (e.g. _total) suffixes are appended.

The escaping choice only sets the default escaping scheme. A scrape request that negotiates an escaping scheme (via the escaping parameter of the Accept header, supported by the version 1.0.0 and later text formats) always takes precedence over the configured strategy. The classic (pre-1.0.0) text formats do not support escaping negotiation and are always emitted using underscore escaping; the suffix choice applies to every format.

Troubleshooting

This component uses an EventSource with the name "OpenTelemetry-Exporter-Prometheus" for its internal logging. Please refer to SDK troubleshooting for instructions on seeing these internal logs.

References

• OpenTelemetry Project
• Prometheus