Use single NullHandler for whole library

I was trying to get a feel for what the rest of the python ecosystem
does with its logging, so I looked into the top few libraries on pypi:

urllib3 maintains a logger for not quite every module, but for each
one that does heavy lifting. The logger name is `__name__`, and no
handlers are registered for any module-level loggers, including
NullHandler. Their documentation spells out how to configure logging
for the library.

They explicitly configure a library root-level logger called `urllib3`
to which they attach a `NullHandler`. This addresses the "no handlers
could be found" problem.

Their tests explicitly configure handlers, just like ours do.

scrapy is more hands-on. It provides a configuration module for its
logging and a whole document on how to handle logging with scrapy. It
looks like log.py's whole reason for existence is making sure that a
handler is attached to to the scrapy handler at startup.

I think the extra complexity here is because scrapy also offers a CLI,
so there has to be some way to configure logging without resorting to
writing python, so I felt we didn't need to resort to this added
complexity.

---

Based on all of the libraries I've looked at, I think our current
approach is reasonable. The one change I would make is to explicitly
configure a `grpc` logger and to only attach a `NullHandler` to it
instead of putting the burden on the author of each new module to
configure it there.

With this change, I have

- Configured a logger in each module that cares about logging
- Removed all NullHandlers attached to module-level loggers
- Explicitly configured a `grpc` logger with a `NullHandler` attached

Resolves: #16572
Related: #17064

1 files changed, 3 insertions, 1 deletions

diff --git a/src/python/grpcio/grpc/__init__.py b/src/python/grpcio/grpc/__init__.py
index df98dd10ad..8c15e54082 100644
--- a/src/python/grpcio/grpc/__init__.py
+++ b/src/python/grpcio/grpc/__init__.py
@@ -15,12 +15,14 @@
 
 import abc
 import enum
+import logging
 import sys
-
 import six
 
 from grpc._cython import cygrpc as _cygrpc
 
+logging.getLogger(__name__).addHandler(logging.NullHandler())
+
 ############################## Future Interface  ###############################