I've created this package so you can easily integrate App.Metrics into you ASP WEB API to send collected metrics to an InfluxDB2 Server with Prometheus Text Formatter (/metrics-text).

The setup is very straightforward, just install the Nuget Package, add the config section to your appsettings.json and inject the services into your program.cs.

Please follow the instructions carefully.

Install Nuget:

dotnet add package JF91.AppMetrics.InfluxDb2WithPrometheus --version 1.0.2

1 - Add this section to your appsettings.json and modify it to your needs:

"MetricsOptions": {
    "DefaultContextLabel": "MyCustomContext",
    "Enabled": true
},
    "MetricsWebTrackingOptions": {
    "ApdexTrackingEnabled": true,
    "ApdexTSeconds": 0.1,
    "IgnoredHttpStatusCodes": [ 404 ],
    "IgnoredRoutesRegexPatterns": [],
    "OAuth2TrackingEnabled": true
},
    "MetricEndpointsOptions": {
    "MetricsEndpointEnabled": true,
    "MetricsTextEndpointEnabled": true,
    "PingEndpointEnabled": true,
    "EnvironmentInfoEndpointEnabled": true
},
    "MetricsReportingInfluxDb2Options": {
    "InfluxDb2": {
    "BaseUri": "http://127.0.0.1:8086",
    "Organization": "metrics",
    "Bucket": "metrics",
    "Token": "changeme"
},
    "HttpPolicy": {
    "BackoffPeriod": "0:0:30",
    "FailuresBeforeBackoff": 5,
    "Timeout": "0:0:40"
},
    "ReportInterval": "0:0:1"
}

2 - Add this Environment Variable to your launchSettings.json:

"APPLICATION_NAME": "MyKickassApi"

3 - Add this before builder.Build():

builder.Services.AddMetricsServices();
builder.WebHost
    .AddInfluxDb2AppMetrics(builder.Configuration)
    .AddPrometheusAppMetrics();

4 - Add this after builder.Build():

app.UseRequestsCounterMiddleware();
app.UseRequestsDurationMiddleware();
app.UseResponsesSizeMiddleware();
app.UseResponsesApdexMiddleware();
app.UseMetricsAllMiddleware();
app.UseMetricsAllEndpoints();

5 - Add this before app.Run():

app.UseHttpStatusCodesCounterMiddleware();

---

How to add a new metrics middleware:

1 - Create an interceptor middleware;

2 - Inject IMetrics;

public class MyNewMetricMiddleware
{
    private readonly RequestDelegate _next;
    private readonly IMetrics _metrics;

    public MyNewMetricMiddleware(RequestDelegate next, IMetrics metrics)
    {
        _next = next;
        _metrics = metrics;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        try
        {
            await _next(context);

            var tags = new MetricTags
            (
                new[] { "Tag1-Key", "Tag2-Key" },
                new[] { "Tag1-Value, "Tag2-Value }
            );

            _metrics.Measure.Counter.Increment
            (
                new CounterOptions
                {
                    Name = "my-new-metric",
                    Context = "my-new-context",
                    MeasurementUnit = Unit.Calls,
                    Tags = tags
                }
            );
        }
        catch (Exception ex)
        {
        }
    }
}

3 - Add middleware to app pipeline:

builder.UseMiddleware<MyNewMetricMiddleware>();

---

How to add a new metrics in controller:

1 - Inject IMetrics into controller:

public WeatherForecastController(ILogger<WeatherForecastController> logger, IMetrics metrics)
{
    _logger = logger;
    _metrics = metrics;
}

2 - Use IMetrics:

[HttpGet(Name = "GetWeatherForecast")]
public IEnumerable<WeatherForecast> Get()
{
    var tags = new MetricTags
    (
        new[] { "Tag1-Key", "Tag2-Key" },
        new[] { "Tag1-Value, "Tag2-Value }
    );
    
    _metrics.Measure.Counter.Increment
    (
        new CounterOptions
        {
            Name = "my-new-metric",
            Context = "my-new-context",
            MeasurementUnit = Unit.Calls,
            Tags = tags
        }
    );

    return Enumerable.Range(1, 5).Select
        (
            index => new WeatherForecast
            {
                Date = DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
                TemperatureC = Random.Shared.Next(-20, 55),
                Summary = Summaries[Random.Shared.Next(Summaries.Length)]
            }
        )
        .ToArray();
}