Python-wrapper: Use debug flag to provide useful information

[epa095]

The python model microservice accepts a debug-flag, but it does not use it for anything. It seems reasonable for it to use it for at least two things:

• Pass it along to the flask server, so it can be in debug/non-debug mode, and
• Provide different level of logging. For the latter I recommend using the logging module in Python instead of "print" statements scattered around in the code:
  • On the top of the class get the logger with logger = logging.getLogger(__name__)
  • Around in the code log to different levels, using e.g. logger.debug or logger.info
  • Set the loglevel of the logger based on the debug toggle.

[ukclivecox]

These changes make sense. We are updating the python code to create a Seldon module for easier testing (#306) and usage and we can add these changes into that. @jklaise

[masonlr]

@cliveseldon #306 was merged, but did hot-reloading make it into the seldon_core.microservice module?

Hot-reloading would be useful for iterative development. A use case would be to mount local files into a model container using something like:

docker run -it -p 5000:5000 -v ${PWD}:/microservice name:version /bin/bash

then run a debug mode from within the container (although with a --debug flag, or a DEBUG environment variable, etc.)

seldon-core-microservice Model REST --service-type MODEL --debug 

and then be able to make local file changes and see the model hot-reload. The change would be to support passing debug variable state through to (https://github.com/SeldonIO/seldon-core/blob/master/python/seldon_core/microservice.py#L224):

 app.run(host='0.0.0.0', port=port, debug=True)

A hot-reload option might also be useful for accelerating k8s iterative development if using dev tools like skaffold filesync (https://skaffold.dev/docs/how-tos/filesync/).

[ukclivecox]

This sounds useful. You happy to do a PR for adding that to debug mode?

[masonlr]

Yes can do. Do you have a preference for the interface? i.e. --debug flag or specific env variable?