Feature Request: Attach log messages to Activity.Events

[This came out of a discussion on gitter with @jchannon.]

Feature Request

OpenTracing.Contrib.NetCore will register an ILoggerProvider\ILogger which will attach log messages to a span and these are exported to Jaeger.

The ask is to have a similar mechanism in OpenTelemetry .NET.

Design

Our JaegerExporter is already coded to convert ActivityEvents into JaegerLogs: https://github.com/open-telemetry/opentelemetry-dotnet/blob/6fe93f8d79725d696e01090ab531585881636850/src/OpenTelemetry.Exporter.Jaeger/Implementation/JaegerActivityExtensions.cs#L158-L175

Given that behavior, the idea is to add a BaseProcessor<LogRecord> which will convert log messages written through ILogger into ActivityEvents and add them to Activity.Current.Events. Presumably only when Activity.IsAllDataRequested = true but this could be configurable.

This will be something you will have to explicitly turn on because it is expensive.

Proposed API

Coming soon…

[iSeiryu]

@CodeBlanch Something like this? https://github.com/iSeiryu/opentelemetry-dotnet/commit/c13208510f8139bdeac966298fd911db31170dcd

Since there is no proper example for classes like that (the only existing one is for Console and it uses BaseExporter<LogRecord> instead of BaseProcessor<LogRecord>) I probably messed up some naming conventions.

I tested it on local and it works. It logs general system and custom logs as well as the exceptions. I left the options empty but I’m sure it would require some configuration.

[CodeBlanch]

The logging code in 1.0 registers an ILoggerProvider which will create ILoggers that call this line:

https://github.com/open-telemetry/opentelemetry-dotnet/blob/3239e5b02f639779d93b22427fece7370579432b/src/OpenTelemetry/Logs/OpenTelemetryLogger.cs#L52

Any time a log message is written, the registered BaseProcessor<LogRecord> will be called. The problem is, there’s no BaseProcessor<LogRecord> implementation in there. If you build your own, you can make it work.

That’s exactly what I’m going to do for this issue/feature. I’m going to create a BaseProcessor<LogRecord> that adds the log messages to Activity.Events so they will export to Jaeger. Now that 1.0 is out, I’ll get back to that. But if you want to give it a shot feel free 😄

Also, if I’m using Serilog in an ASP.NET Core application, will this still work?

Only if you are using serilog-extensions-logging which will write through ILogger before Serilog’s custom logger.