Daemon/Background service metrics

[dylan-asos]

Hi,

We're collecting metrics from our dotnet Web APIs using the Open Telemetry package OpenTelemetry.Exporter.Prometheus.AspNetCore, which we're initialising at startup with a call to UseOpenTelemetryPrometheusScrapingEndpoint to expose Prometheus metrics for scraping - this is deployed on Azure Kubernetes Service. All is good - metrics are exposed on the port we configure in UseOpenTelemetryPrometheusScrapingEndpoint .

We also have a number of Daemon processing jobs (message processors and other event triggered background jobs) we'd like to expose metrics for scraping.

Is there a recommended package/approach/example for exporting Prometheus metrics for scraping from a Background worker service? Example skeleton code of the type of app we'd be building.

public class Program
{
    public static async Task Main(string[] args)
    {
        var builder = CreateBuilder(args);
        var host = Build(builder);
        await host.RunAsync();
    }

    public static IHostBuilder CreateBuilder(params string[] args)
    {
        var builder = Host.CreateDefaultBuilder(args);
        builder.ConfigureServices(ConfigureServices);
        return builder;
    }

    public static IHost Build(IHostBuilder builder)
    {
        return builder.Build();
    }

    private static void ConfigureServices(HostBuilderContext context, IServiceCollection services)
    {
        services.AddHostedService<Worker>();
    }
}

The package OpenTelemetry.Exporter.Prometheus.HttpListener does what I want, e.g. just call

        builder.SetResourceBuilder(ResourceBuilder.CreateDefault().AddService(serviceName));
        builder.AddPrometheusHttpListener(
            options => options.UriPrefixes = new[] {"http://localhost:9464/"});

and that would expose that endpoint which could be scraped. However, the statement in the package page about no plans for production & mentioning different packages is making me question if this is the correct approach.

[paulredert]

I have the same question. What approach can we follow when creating background worker services? Any news?

[cijothomas]

If you are using an Asp.Net Core web app with some background worker in it (i.e same process), then the existing Prometheus.AspNetCore can be used. If you are running a pure worker service which do not by itself run a webserver, then you are limited to using OTLP Exporter only. (unless you want to upgrade it to a webserver, at which point its no diff. than regular asp.net core webhost) The warning in Prometheus.HttpListener is true, and already suggests the approach of using OTLP+collector->prometheus

[Charlotte-br560]

Absolutely! To expose Prometheus metrics for scraping from a background worker service, you might consider using the OpenTelemetry.Exporter.Prometheus.HttpListener package. Despite the mention of no plans for production, it could still be a viable approach for your use case.

Here's a simplified example of integrating it into your existing worker service:

`public class Program
{
public static async Task Main(string[] args)
{
var builder = CreateBuilder(args);
var host = Build(builder);
await host.RunAsync();
}

public static IHostBuilder CreateBuilder(params string[] args)
{
    var builder = Host.CreateDefaultBuilder(args);
    builder.ConfigureServices(ConfigureServices);
    return builder;
}

public static IHost Build(IHostBuilder builder)
{
    return builder.Build();
}

private static void ConfigureServices(HostBuilderContext context, IServiceCollection services)
{
    services.AddHostedService<Worker>();
    ConfigureOpenTelemetry(services);
}

private static void ConfigureOpenTelemetry(IServiceCollection services)
{
    services.AddOpenTelemetryTracing(builder =>
    {
        // Your other tracing configurations

        builder.SetResourceBuilder(ResourceBuilder.CreateDefault().AddService("your-service-name"));

        builder.AddPrometheusHttpListener(options =>
        {
            options.UriPrefixes = new[] { "http://localhost:9464/" };
        });
    });
}

}
`
This should provide you with the Prometheus metrics endpoint for scraping from your background worker service. Feel free to adjust the configurations based on your specific requirements. Happy coding!