Self-diagnostics log file has strange content

[mkotsabiuk]

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.

[cijothomas]

@xiang17 could you take a quick look and see if this is expected?

[mkotsabiuk]

Thanks, @cijothomas, for assigning @xiang17 to check it.

[xiang17]

It is expected behavior. The file was never intended to be in a proper text format. The log is written in a fixed-size file in a circular way. Once reached to the end, the self-diagnostics module will even overwrite the log file with new logs from beginning.

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).

[mkotsabiuk]

Thank you, @xiang17, for explaining. I think it worth it to add this behavior into Remarks section because it was unexpected for me and I thought that I am doing something in the wrong way.

Does fixing it and making the log file to be in a proper text format will require a big overhead to SDK itself?

[mkotsabiuk]

Hi @xiang17,

Any updates on this issue?

cc: @cijothomas @reyang

[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.

[Oberon00]

@xiang17

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

What is the expected way to use this file then?