Altinn.AspNet.HealthChecks.OpenTelemetry 0.3.0

Altinn.AspNet.HealthChecks.OpenTelemetry

Experimental — pre-1.0.0. APIs may change without notice before the 1.0.0 release.

OpenTelemetry companion package to Altinn.AspNet.HealthChecks: a span processor that drops the noisy ASP.NET Core server spans produced by health check probes, so /health* traffic does not flood your traces.

Usage

tracerProviderBuilder
    .AddHealthCheckActivityFilter() // suppresses the five default /health* endpoints
    .AddOtlpExporter();             // exporters must be registered after the filter

Without arguments, the filter suppresses the five endpoints mapped by MapAltinnHealthChecks(): /alive, /health, /health/readiness, /health/startup and /health/deep. Pass your own route suffixes to replace the defaults:

tracerProviderBuilder.AddHealthCheckActivityFilter("/internal/health");

If you customise the endpoint paths, share the options object

The defaults above are hardcoded, so moving a path leaves the filter matching the old one — silently, with no error and no clue beyond a growing trace bill. Pass the same HealthCheckEndpointOptions instance to both, and the two cannot disagree:

var healthEndpoints = new HealthCheckEndpointOptions();
healthEndpoints.Deep.Path = "/internal/health/deep";
healthEndpoints.Startup.Disable();

builder.Services.AddOpenTelemetry().WithTracing(t => t
    .AddHealthCheckActivityFilter(healthEndpoints)   // suppresses exactly what gets mapped
    .AddOtlpExporter());

app.MapAltinnHealthChecks(healthEndpoints);

Disabled endpoints are not suppressed: nothing is mapped there, so a route ending that way belongs to your app and its spans are kept.

Matching is by case-insensitive route suffix, so the endpoints stay suppressed when the app is mounted under a path base. The flip side: any route ending in a suffix is suppressed too — if your API has a business route like /api/devices/{id}/health, its spans are dropped under the defaults. Pass explicit, more specific suffixes in that case.

How it works

The filter is a span processor that clears the Recorded flag on ASP.NET Core server spans whose http.route (or url.path) ends with one of the configured suffixes. Export processors skip spans that are not recorded, so the span reaches no exporter — but only exporters added after the filter, since processors run in registration order.

The decision is made when the server span ends, so child spans created while the probe ran (a database call inside a deep check, say) are still exported. To drop the whole trace, filter at the instrumentation level instead — that also avoids creating the span in the first place:

tracerProviderBuilder.AddAspNetCoreInstrumentation(o =>
    o.Filter = ctx => !ctx.Request.Path.StartsWithSegments("/health"));

Target frameworks

net8.0, net9.0, net10.0.