Make client logging configurable

[grantwwu]

Is your feature request related to a problem? Please describe.
The Python and Go client libraries log - a lot. It's annoying especially if you're trying to use a form of structured logging, or just debug something you know is unrelated to Pulsar.

Describe the solution you'd like
At bare minimum, there should be a way to just turn it off.

A more complete solution would allow configuring the logger in a way idiomatic to each language. For example, integrating with Python logging. I'm not 100% sure how.

Another option would be to allow redirecting the logs to a file instead of polluting stderr.

Describe alternatives you've considered
Not sure if there's a good alternative.

[merlimat]

@grantwwu In Go it's already possible to configure. Take a look at the Logger in ClientOptions:
https://godoc.org/github.com/apache/pulsar/pulsar-client-go/pulsar#ClientOptions

We should do something similar for Python as well and probably move the logger to Py logging by default.

[merlimat]

C++ lib has a setLogger() method that we'd need to hook up in the Python bindings: https://pulsar.apache.org/api/cpp/classpulsar_1_1_client_configuration.html#aa0dc0968fea7621352aae5a82bda7222

[grantwwu]

Good to know for Go. Definitely would love this in Python as well.

[chairmank]

The logging module in the Python standard library is implemented in Python. It is not a built-in module implemented in C.

I think that we could implement a log4cxx appender that uses boost::python::exec to call methods on a Python standard library Logger instance, with arguments passed as locals.

[tiwansh]

The client logging in python still seems non-configurable even after providing the log4cxx config file. Is it possible to configure to stop logging to stdout ?

[rosejn]

It seems maybe this got held up due to the potential difficulty of sending log data from C++ up to python. How about just providing options to silence logging, and/or set the log level in the meantime?