Recording OTel LLM metrics to .NET Aspire fails #1407
Description
Recording OTel LLM metrics to .NET Aspire fails with the following exception:
fail: Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware[1]
An unhandled exception has occurred while executing the request.
Google.Protobuf.InvalidProtocolBufferException: String is invalid UTF-8.
---> System.Text.DecoderFallbackException: Unable to translate bytes [88] at index 1 from specified code page to Unicode.
at System.Text.DecoderExceptionFallbackBuffer.Throw(Byte[] bytesUnknown, Int32 index)
at System.Text.DecoderExceptionFallbackBuffer.Fallback(Byte[] bytesUnknown, Int32 index)
at System.Text.Encoding.GetCharCountWithFallback(ReadOnlySpan`1 bytes, Int32 originalBytesLength, DecoderNLS decoder)
at System.Text.Encoding.GetCharCountWithFallback(Byte* pBytesOriginal, Int32 originalByteCount, Int32 bytesConsumedSoFar)
at Google.Protobuf.ParsingPrimitives.ReadRawString(ReadOnlySpan`1& buffer, ParserInternalState& state, Int32 length)
--- End of inner exception stack trace ---
at Google.Protobuf.ParsingPrimitives.ReadRawString(ReadOnlySpan`1& buffer, ParserInternalState& state, Int32 length)
at OpenTelemetry.Proto.Common.V1.KeyValue.pb::Google.Protobuf.IBufferMessage.InternalMergeFrom(ParseContext& input) in /_/artifacts/obj/Aspire.Dashboard/linux-x64/Release/net8.0/linux-x64/opentelemetry/proto/common/v1/Common.cs:line 1254
at Google.Protobuf.ParsingPrimitivesMessages.ReadMessage(ParseContext& ctx, IMessage message)
at Google.Protobuf.Collections.RepeatedField`1.AddEntriesFrom(ParseContext& ctx, FieldCodec`1 codec)
at OpenTelemetry.Proto.Trace.V1.Span.pb::Google.Protobuf.IBufferMessage.InternalMergeFrom(ParseContext& input) in /_/artifacts/obj/Aspire.Dashboard/linux-x64/Release/net8.0/linux-x64/opentelemetry/proto/trace/v1/Trace.cs:line 1615
at Google.Protobuf.ParsingPrimitivesMessages.ReadMessage(ParseContext& ctx, IMessage message)
at Google.Protobuf.Collections.RepeatedField`1.AddEntriesFrom(ParseContext& ctx, FieldCodec`1 codec)
at OpenTelemetry.Proto.Trace.V1.ScopeSpans.pb::Google.Protobuf.IBufferMessage.InternalMergeFrom(ParseContext& input) in /_/artifacts/obj/Aspire.Dashboard/linux-x64/Release/net8.0/linux-x64/opentelemetry/proto/trace/v1/Trace.cs:line 844
at Google.Protobuf.ParsingPrimitivesMessages.ReadMessage(ParseContext& ctx, IMessage message)
at Google.Protobuf.Collections.RepeatedField`1.AddEntriesFrom(ParseContext& ctx, FieldCodec`1 codec)
at OpenTelemetry.Proto.Trace.V1.ResourceSpans.pb::Google.Protobuf.IBufferMessage.InternalMergeFrom(ParseContext& input) in /_/artifacts/obj/Aspire.Dashboard/linux-x64/Release/net8.0/linux-x64/opentelemetry/proto/trace/v1/Trace.cs:line 560
at Google.Protobuf.ParsingPrimitivesMessages.ReadMessage(ParseContext& ctx, IMessage message)
at Google.Protobuf.Collections.RepeatedField`1.AddEntriesFrom(ParseContext& ctx, FieldCodec`1 codec)
at OpenTelemetry.Proto.Collector.Trace.V1.ExportTraceServiceRequest.pb::Google.Protobuf.IBufferMessage.InternalMergeFrom(ParseContext& input) in /_/artifacts/obj/Aspire.Dashboard/linux-x64/Release/net8.0/linux-x64/opentelemetry/proto/collector/trace/v1/TraceService.cs:line 241
at Aspire.Dashboard.Otlp.Http.OtlpHttpEndpointsBuilder.MessageBindable`1.<>c.<BindAsync>b__5_0(ReadOnlySequence`1 data) in /_/src/Aspire.Dashboard/Otlp/Http/OtlpHttpEndpointsBuilder.cs:line 121
at Aspire.Dashboard.Otlp.Http.OtlpHttpEndpointsBuilder.ReadOtlpData[T](HttpContext httpContext, Func`2 exporter)
at Aspire.Dashboard.Otlp.Http.OtlpHttpEndpointsBuilder.MessageBindable`1.BindAsync(HttpContext context, ParameterInfo parameter)
at Microsoft.AspNetCore.Http.ParameterBindingMethodCache.<ConvertValueTask>g__ConvertAwaited|26_0[T](ValueTask`1 typedValueTask)
at Microsoft.AspNetCore.Http.RequestDelegateFactory.<>c__DisplayClass101_0.<<HandleRequestBodyAndCompileRequestDelegate>b__0>d.MoveNext()
--- End of stack trace from previous location ---
at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Diagnostics.StatusCodePagesMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddlewareImpl.<Invoke>g__Awaited|10_0(ExceptionHandlerMiddlewareImpl middleware, HttpContext context, Task task)
As a result, no metrics are recorded and displayed in the dashboard. Spans show just fine.
To reproduce, track LLM usage from Azure OpenAI using Dev Proxy v1.2.0.