MassTransit metrics for Prometheus

Description

This library allows you collecting four important metrics for MassTransit consumers and send them to Prometheus. Those metrics are:

• app_message_processing_time_seconds - the time it takes to consume one message
• app_message_critical_time_seconds - the total time between when the message was sent and when it was consumed
• app_message_count - the total number of messages received
• app_message_failures_count - the number of messages that failed processing

All metrics are labeled with two labels:

• service_name - the name of your application or service
• message_type - the type of message for which the metrics are collected

Prometheus client library

We use Nexogen.Libraries.Metrics library as a Prometheus client. The client itself is not included as a reference, we only use the core and the extension libraries.

Check the GitHub repository for more details about the client library we use.

Usage

First, you need to add metrics to your application. Start by adding the client library to your project using a NuGet package:

dotnet add package Nexogen.Libraries.Metrics.Prometheus

Metrics need to be available via an HTTP endpoint, by default it is /metrics. Add the ASP.NET Core integration package to get this endpoint out-of-the-box:

dotnet add package Nexogen.Libraries.Metrics.Prometheus.AspCore

Then, create Prometheus metrics object and register it in the services collection. The same instance should be used to configure the bus:

public void ConfigureServices(IServiceCollection services)
{
    var metrics = new PrometheusMetrics();
    
    services.AddSingleton(Bus.Factory.CreateUsingRabbitMq(cfg =>
    {
        cfg.UsePrometheusMetrics(metrics);
    
        var host = cfg.Host(new Uri("rabbitmq://localhost"), h => 
        {
            h.UserName("guest");
            h.Password("guest");
        });

        cfg.ReceiveEndpoint(host, "myqueue", e =>
        {
            e.Consumer<MyMessageConsumer>();
        });
    }));
    
    services.AddPrometheus(metrics);
    
    // other services
}

Finally, add Prometheus integration to the service configuration:

public void Configure(IApplicationBuilder app)
{
    app.UsePrometheus();
}