Add an `Enabled` method to Logger

[MrAlias]

Add an `Enabled` method to Logger

[pellared]

This will be probably also handy for implementing following bridges:

• logr - see: https://pkg.go.dev/github.com/go-logr/logr#LogSink
• zap - see: https://pkg.go.dev/go.uber.org/zap/zapcore#LevelEnabler

[pellared]

For logrus I think the bridge would implement https://pkg.go.dev/github.com/sirupsen/logrus#Hook

[MrAlias]

What about No-Op Loggers?

[pellared]

This invalidates this rejected proposal https://github.com/open-telemetry/opentelemetry-go/blob/main/log/DESIGN.md#add-xyz-method-to-logger.

I have put the issue to GA project to at least discuss it before we moving it to post-GA.

[MrAlias]

open-telemetry/opentelemetry-specification#3917

[MrAlias]

This will be probably also handy for implementing following bridges:

• logr - see: https://pkg.go.dev/github.com/go-logr/logr#LogSink
• zap - see: https://pkg.go.dev/go.uber.org/zap/zapcore#LevelEnabler

Also, possibly, logrus: https://pkg.go.dev/github.com/sirupsen/logrus#Logger.IsLevelEnabled

[pellared]

If the bridge accepts some sort of minimum level things will be logged at

This was the idea

it can be different than what the LoggerProvider that bridge also accepts is configured to minimally log

As far as I remember, the SDK's logger provider configuration does not accept a severity level. Same for logger method. I think that without any of it adding Enabled to the Bridge API would not make much sense.

[MrAlias]

I also think it should be added to the pipeline. If an exporter is only configured to export at a min level there needs to be a way to tell the SDK and user not to do things.

This is an operator concern, not one for instrumentation.

[MrAlias]

Use cases from other languages

otel-rust added a similar method under feature flag - open-telemetry/opentelemetry-rust#1147
otel-cpp also has a similar approach - https://github.com/open-telemetry/opentelemetry-cpp/blob/07f6cb54ece56691dbd2a94b0cbeec722ff6a631/api/include/opentelemetry/logs/logger.h#L259

Originally posted by @lalitb in open-telemetry/opentelemetry-specification#3917 (comment)