Self-diagnostics log file has strange content

Bug Report

I am using OpenTelemetry 1.1.0 (commit ce46d001d5ed08d91e7750b4859410330d57e7a7). Running [AspNetCore example] (https://github.com/open-telemetry/opentelemetry-dotnet/tree/main/examples/AspNetCore) with target framework netcoreapp3.1, release configurations and OTEL_DIAGNOSTICS.json config file:

{
    "LogDirectory": ".",
    "FileSize": 1024,
    "LogLevel": "LogAlways"
}

After some requests to https://localhost:5001/WeatherForecast/ the log file Examples.AspNetCore.exe.41136.log was created.

Examples.AspNetCore.exe.41136.log

When I open .log file in Notepad++ I see there internal events generated by OpenTelemetry (logs) with some unsupported symbols:

But I am expecting to see there only logs.

[Oberon00]

@xiang17

The file was never intended to be in a proper text format.

What is the expected way to use this file then?

[Oberon00]

I would also like to have that documented.

The reason is described in #1258: The self-diagnostics module is designed to have minimal overhead and bounded resource usage to make it production-ready and developers worry-free from ever-growing log file(s).

This will lead to even stranger content when the file starts again from the beginning, especially if this happens mid-stacktrace and you get something that looks like a normally formatted stack trace with impossible content.

I don’t think “minimal-overhead” in that extreme sense is a desirable feature. I’d rather want a developer-friendly debug feature by default.