Pass the context to the telemetry hooks

[StarpTech]

Hi, it would be very useful if we would have access to the producer context in the telemetry hooks. This would allow us to trace application specific and connect metrics points specific to the trace in the context. This would work with OpenTelemetry.

My proposal is to pass the ctx as the first parameter to the functions.

[twmb]

Which context? The client context closes only when the client is closed. I'm not opposed, although this doubles the surface area of hooks for a pretty marginal gain. Would you be open to contributing this?

[StarpTech]

I was referring to the context passed to Produce

[twmb]

Which hook?

[0xjac]

I'm not sure how related this is (if not, I'll happily open a new issue) but I also need the context passed down to get trace info, specifically to logs.

This would allow to modify the logger adapters and for the specific loggers which support passing the context (such as zerolog, see the TracingHook example).

This change might however break the kgo.Logger interface and in turn any custom logger implementations. So a better approach might be to pass the context as a field and in the adapters to set it as the context if possible or ignore it. This would still impact custom logger implementations as they would now start logging the context as a field but their logging should continue to work and the fix might be easy to apply.

[StarpTech]

@twmb all hooks that are executed after producing. In our specific case, I referring to OnBrokerWrite

[twmb]

I believe @0xjac has a good solution above,

"So a better approach might be to pass the context as a field and in the adapters to set it as the context if possible or ignore it."

This pairs well with the incoming #907, so that users can use the same context for the logger adapters as they use for the client.

Internally, the context is wrapped in a few places so that it can have a more scoped cancellation. So, whatever context is passed to the adapter would not be able to catch cancellation, but this is pretty minor. Is catching cancellation needed, or is the context being used to pass around values?