Fixing the datahandler logging facility

fix-dh-logging.md

Because the datahandler's logging was written in a huge hurry at the last minute, it's going to need a rewrite:

• A custom object is used for logging instead of django's logging facility; it's already running if you orm.setup().
• The root logger ('') is always hardcoded to talk to a socket; sooner or later we'll need a configuration-based logging config (which again django already provides).
• The custom method, Logger.log, calls python's logging.log, thus losing information as funcName will always be log; the custom extra used instead, caller, is not reliable, as 3rd party libs don't know to use it (we had this problem with RQ).
• In dhd.serve_log, jobid and caller had to be taken out due to above issues with RQ. This is because logging.basicConfig sets a configuration for the root (ie global) logger that makes poor assumptions.
• It's a datahandler logger, not a gips logger. In the long run, there is no meaningful separation between gips logging and datahandler logging, only differential configs based on various use cases.

Fixes for the client side:

• Use django's logging, including existing means to have django read the gips config. This can be used to set the logging server to talk to, etc etc.
• Modules do what they're supposed to do: Log to a named log specific to that part of the application (python's logging tutorial says to use the fully-qualified module name via: l = logging.getLogger(__name__); l.info('message'))
• Go through existing logging class and make sure it's not necessary; any additional wiring (say, saving a jobid) should be done in the pythonic way for logging, maybe via a custom LoggerAdapter:

https://docs.python.org/2/howto/logging-cookbook.html#adding-contextual-information-to-your-logging-output

Fixes for the server side:

• Revise logging.basicConfig call so it makes no assumptions about custom logging anything.
• Set up formatters or other wiring to handle logs whose names match 'gips' or 'gips.datahandler', and thus pick up extra custom info for those logs.

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