OTLP Exporter collects zero metrics on .NET MAUI Android AOT- System.Diagnostics.Metrics registration fails

[LosDavidos]

System.Diagnostics.Metrics completely fails under .NET MAUI Android AOT

Problem Summary

I'm experiencing complete failure of System.Diagnostics.Metrics when running a .NET MAUI Android application with AOT compilation enabled. The OpenTelemetry SDK initializes successfully, but no metrics are ever collected or exported.

Environment

• .NET Version: 10.0 (net10.0-android)
• Platform: Android (Samsung SM-A057G, Android 15)
• OpenTelemetry Version: 1.14.0
• AOT Configuration:

  <RunAOTCompilation>true</RunAOTCompilation> <AndroidAotMode>Hybrid</AndroidAotMode> <AndroidLinkMode>SdkOnly</AndroidLinkMode>

Configuration

services.AddOpenTelemetry() .ConfigureResource(resource => resource .AddService("MobileApp", serviceVersion: "1.0.0") .AddAttributes(new Dictionary<string, object> { { "device.platform", "android" }, { "device.os", DeviceInfo.Platform.ToString() }, { "device.model", DeviceInfo.Model } })) .WithMetrics(metrics => metrics .AddMeter("Mobile") .AddView("photo.capture.time", new ExplicitBucketHistogramConfiguration { Boundaries = new double[] { 100, 200, 300, 500, 1000, 2000, 5000, 10000 } }) .AddOtlpExporter(options => { options.Endpoint = new Uri("https://my-backend.com/metrics"); options.Protocol = OtlpExportProtocol.HttpProtobuf; })); // Create meters and instruments var meter = new Meter("Mobile", "1.0.0"); var appLaunchCounter = meter.CreateCounter<long>("app.launch.total", "1", "Total app launches"); var photoCaptureTime = meter.CreateHistogram<double>("photo.capture.time", "ms", "Photo capture time"); // Record metrics appLaunchCounter.Add(1); photoCaptureTime.Record(1234.5);

Behavior Comparison

Debug Build (works perfectly)

Diagnostic output:

[DIAGNOSTICS] Meter.s_allMeters.Count: 5 [DIAGNOSTICS] MeterListener.InstrumentPublished: called 39 times ✅ Instrument: photo.taken.total ✅ Instrument: photo.capture.time ✅ Instrument: app.launch.total (... all instruments registered) [CONSOLE-EXPORTER] Export batch size: 1 Metric: app.launch.total Value: 1 Tags: device.platform=android, device.model=SM-A057G 

Release Build with AOT (complete failure)

Diagnostic output:

[DIAGNOSTICS] Meter.s_allMeters.Count: 0 ← ⚠️ EMPTY! [DIAGNOSTICS] MeterListener.InstrumentPublished: never called ⚠️ NO INSTRUMENTS PUBLISHED TO LISTENER [CONSOLE-EXPORTER] Export batch size: 0 ⚠️ EMPTY BATCH - No metrics collected! 

Root Cause Analysis

I've traced this to the BCL level - when new Meter("Mobile", "1.0.0") is created under AOT compilation, the meter instance is constructed but never registered in the static Meter.s_allMeters field. This causes MeterListener.InstrumentPublished callbacks to never fire, which means OpenTelemetry SDK never sees any instruments.

To confirm this is not an OpenTelemetry issue, I created a simple test exporter:

public class ConsoleTestMetricExporter : BaseExporter<Metric> { public override ExportResult Export(in Batch<Metric> batch) { var count = 0; foreach (var metric in batch) { count++; Console.WriteLine($"Metric: {metric.Name}, Value: {metric}"); } Console.WriteLine($"[CONSOLE-EXPORTER] Batch size: {count}"); if (count == 0) { Console.WriteLine("[CONSOLE-EXPORTER] ⚠️ EMPTY BATCH"); } return ExportResult.Success; } }

The exporter is called correctly, but the batch is always empty in AOT builds.

What I've Tried

• ✅ LinkerConfig.xml with <assembly fullname="System.Diagnostics.DiagnosticSource" preserve="All" />
• ✅ TrimmerRoots.xml preservation
• ✅ rd.xml runtime directives
• ✅ Disabled linking entirely (AndroidLinkMode=None) - problem persists
• ✅ Verified OpenTelemetry SDK initializes correctly (logs confirm MeterProvider is active)
• ✅ AppContext.SetSwitch("System.Diagnostics.Metrics.Meter.IsSupported", true);

None of these affect the core issue: meters don't register in Meter.s_allMeters under AOT.

Questions

1. Has anyone successfully collected metrics in .NET MAUI Android with AOT enabled? If so, what configuration did you use?

2. Is this a known limitation? Should I file an issue in dotnet/runtime since this appears to be a BCL problem rather than an OpenTelemetry issue?

3. Are there any AOT-compatible alternatives to System.Diagnostics.Metrics that work with OpenTelemetry SDK?

4. Would a custom exporter that bypasses System.Diagnostics.Metrics entirely be a reasonable approach, or is there a better solution?

Related Issues

• system.Diagnostics.Metrics doesn't add my counter in the instrument in case of dotnet MAUI applicaiton when running android emulator using OpenTelemetry  dotnet/maui#21165 - Similar report: metrics work on Windows, fail on Android
• Visualize a OpenTelemetry metric in Prometheus in a MAUI app #4634 - Discussion about MAUI metrics

Additional Context

I can provide full diagnostic logs, sample project, or any other information that would be helpful. The failure is 100% reproducible - Debug builds always work, Release+AOT builds always fail with empty metric batches.

Thank you for any guidance!

[martincostello]

Should I file an issue in dotnet/runtime since this appears to be a BCL problem rather than an OpenTelemetry issue?

Yes, if you're confident the root cause is there.

Are there any AOT-compatible alternatives to System.Diagnostics.Metrics that work with OpenTelemetry SDK?

Not that I'm aware of - the .NET OpenTelemetry SDK builds on top of the .NET APIs (Activity, Meter).

Would a custom exporter ...

I would hold off on that until you've filed a bug with dotnet/runtime - if it's a easily fixable bug that can be backported to servicing branches, then you may only need to wait ~2 months for a patch that fixes it.

---

FYI we have zero CI/test coverage for MAUI scenarios (see #5831). We do however have test coverage for native AoT.

[martincostello]

This issue might also be relevant: dotnet/runtime#120113

[martincostello]

Found the issue you filed. Cross-linking to the apparent answer: dotnet/runtime#124226 (comment)

[martincostello]

Also #4634 (comment)

[LosDavidos]

I've opened a ticket in the dotnet repo and it turned out that there is a parameter which disables metrics in release configuration for Android/iOS:
https://learn.microsoft.com/en-us/dotnet/ios/building-apps/build-properties#metricssupport

So <MetricsSupport>true</MetricsSupport> solves the problem.