Metrics Tag Name became case insensitive after upgrade to dotnet 6

[sergey-bulavskiy]

After update to latest AppMetrics nuggets, our tag names became lowercase, when they were using uppercase. This led to creating different tag - Previously (taken from /metrics) application_number_of_pics{isActive="False"... After application_number_of_pics{isactive="False"...

Code: public static string PicIsActiveTag = "isActive"; new MetricTags(CommonMetrics.PicIsActiveTag, bool.FalseString)

Libraries that were updated (apart from projects switched from 3.1 to dotnet 6):

    <PackageReference Include="App.Metrics.AspNetCore.Mvc" Version="4.1.0" /> // -> 4.3.0
    <PackageReference Include="App.Metrics.Formatters.Prometheus" Version="4.1.0" /> // -> 4.3.0

Maybe we missed some changed defaults or new configuration, help required!

[dima-hx]

Try this one:

Add custom formatter:

public class OwnPrometheusFormatterConstants
{
    public static readonly Func<string, string> LabelNameFormatter =
            labelName => MetricNameRegex.Replace(labelName, "_");
    private static readonly Regex MetricNameRegex = new Regex("[^a-z0-9A-Z:_]");
}

On services configure:

services.AddMetricsEndpoints(opt =>
{
    opt.MetricsTextEndpointOutputFormatter = new MetricsPrometheusTextOutputFormatter(new MetricsPrometheusOptions
    {
        LabelNameFormatter = OwnPrometheusFormatterConstants.LabelNameFormatter
    });
    opt.MetricsEndpointOutputFormatter = new MetricsPrometheusProtobufOutputFormatter(new MetricsPrometheusOptions
    {
        LabelNameFormatter = OwnPrometheusFormatterConstants.LabelNameFormatter
    });
}