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 prometheus-net library as a Prometheus client since it is the one that is mentioned on the Prometheus client list.

Usage

Below you can find out how to add metrics to your ASP.NET Core application and register MassTransit metrics.

Install packages

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 prometheus-net
dotnet add package MassTransit.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 prometheus-net.AspCore

Then use one of two ways to register metrics for MassTransit, shown below.

IMPORTANT: Don't use both ways, otherwise you get all counters doubled.

Using middleware

Middleware connects to the consume pipeline.

public void ConfigureServices(IServiceCollection services)
{
    PrometheusMetrics.TryConfigure("my_service");
    
    // this registration is simplified
    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>();
        });
    }));
    
    // other services
}

Using observer

Observer needs to be connected to the IBusControl instance before starting the bus.

public void ConfigureServices(IServiceCollection services)
{
    PrometheusMetrics.TryConfigure("my_service");
    
    var busControl = 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>();
            });
        });
    busControl.ConnectMetrics("my_service");

    // this registration is simplified
    services.AddSingleton(bus);
    
    // other services
}

Final step

Finally, add Prometheus integration to the service configuration:

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