Add config option to disable contracts

[alexanderdean]

In production, all checks can be disabled using the function contracts.disable_all(), so the performance hit is 0.

[fblundun]

This thread has some information about disable_all:

http://www.reddit.com/r/Python/comments/1mrv5m/announcement_pycontracts_16_adds_contractsmeta/

To completely eliminate the performance hit, it looks like we would need to make sure that disable_all gets called before the decorated methods get loaded at all, not just before they get called.

[fblundun]

That could involve something like:

def initialise(disable_contracts):
    if disable_contracts: contracts.disable_all()
    import payload  # so that the payload.py contracts don't cause any overhead
    class Tracker:
        # the tracker class
    return Tracker

The new invocation code would be:

from snowplow_tracker.tracker import initialise
tracker = initialise(True)("d3rkrsqld9gmqf.cloudfront.net")

Is it worth doing this to stop the small performance hit caused by loading the decorated methods before disabling checks?

[alexanderdean]

My gut says no. A small startup hit is not the problem - because most Python apps are long running processes (e.g. Django servers). The problem is more the tiny hit on every event. So I think something simpler that just disables for the tracking, not the initialization, is fine.

[alexanderdean]

Done, closing.