Add logging callback

[belak]

It would be awesome if there was a way to log when users connect (along with what requests they run) and disconnect.

[progrium]

Great idea. The details of this are tricky. Have a proposal?

[belak]

We cheated and just passed a *logrus.Entry to the ssh server... however this isn't optimal because it locks you into a specific logging library. Maybe a callback like this: type LogCallback func(ctx *context.Context, logLevel, message string) LogLevel could optionally be defined as a const... and if you wanted to this could be called for errors as well (combined with #9)

EDIT: The other option would be to define some sort of logging interface, but I'd rather stay away from that if possible because it limits what you can do... for instance, it makes it harder to grab fields out of the context and pass them as params to the logging library.

[progrium]

Btw, join our Slack and maybe #golang if you want to coordinate/discuss more about these improvements. http://slack.gliderlabs.com/

[hloeffler]

do you know any good example of logging callbacks in a go library?

[progrium]

@hloeffler not great examples. annoying examples are often callbacks with string message argument. annoying because it's really not so much a log and more an event in some cases. it might be processes by the app, or it might be logged using structured logging.

[bokunodev]

can we just define signature for the callback and let the user to format or log it however they want?