Application Insights reporter for App.Metrics

Usage

Install nuget package: App.Metrics.Reporting.ApplicationInsights
Obtain Application Insights instrumentation key.
Configure App.Metrics like so:

var instrumentationKey = "00000000-0000-0000-0000-000000000000";

var metrics = new MetricsBuilder()
    .Configuration.Configure(metricsOptions)
    .Report.ToApplicationInsights(instrumentationKey)
    .Build();

How it works

App.Metrics pre-aggregates metrics and reporters are responsible for publishing such aggregated data. Application Insights's type MetricTelemetry is used to describe pre-aggregated metrics and method Track(ITelemetry telemetry) of TelemetryClient publishes it.

It just boils down to translating MetricsDataValueSource into IEnumerable<MetricTelemetry> and publishing the collection using TelemetryClient.

Known issues / shortcomings

1. Aggregation scope

With regards to pre-aggregated data statistics (min, max, stddev) there are two types of App.Metric value sources:

Configurable cumulative - (counter), which are indefinately cummulative by default, but can be configured in their respective options using property ResetOnReporting to start new aggregation scope when the last one is reported.
Indefinately cumulative - (meter, histogram, apdex, timer), which means that they will start new aggregation scope only when IMetricsRoot is created (in practice this usually means when application restarts).

AI clearly favors the first approach.
It is what TelemetryClient does when non-pre-aggregation API (.GetMetric("mycounter").TrackValue(2)) is used and therefore aggregation strategy is under its control. I guess mostly because data statistics min, max, stddev are really only useful for describing smaller batches of uploaded data and not the whole "ever recorded" scope.

Bottom line is: when using App.Metric as a facade to Application Insights do not rely on metric properties min, max, stddev as they will contain something else than you would expect (compared to using TelemetryClient alone for example).

2. Metric dimensions in Azure Portal / Applications Insights

"Dimension" is primarily a term used in Application Insights; the App.Metrics synonym is "item" as in Meter.Mark(MeterOptions options, long amount, string item).

MetricTelemetry does not have a way how to explicitly report dimensions, so this reporter reports them as new metric records with names derived for the parent one.

For example: if on the App.Metric side you would have a single metric "fruit_count" with two dimensions "apples" and "pears" than three metrics will be reported to Application Insights: "fruit_count", "fruit_count.apples" and "fruit_count.pears".