Performance improvement

[Proper-Job]

After pouring over the imagekit code I believe I have found the culprit that causes the major performance problems voiced in: #325, #375, #256, #250
Starting with Django >= 1.7 every call to retrieve a generator would erroneously run the imagekit.utils.autodiscover routine. This fix allows the routine to be run only once.

[vstoykov]

Thank you for your contribution!

Actually the problem that you are fixing is a regression in ImageKit 4 introduced by me on 22 March 2017 (7551936) which is long time after mentioned issues where made.

Now when I'm looking again at that code I'm wondering if you can fix it a little bit more. Remove the logic for checking _autodiscovered in _autodiscover_modules_fallback and setting _autodiscovered to True to be made only in autodiscover() no mather which autodiscover_modules function was called.

We need to continue investigating the performance issues described in mentioned above issues.

[Proper-Job]

Hi @vstoykov
I made the changes you requested.
Even though this doesn't fix the original problem, I was able to cut my current response times in half using this fix. I believe this fix alone merits a maintenance release. What do you think?
I guess we'll just have to keep looking for the original problem after this ;)

[vstoykov]

Yes I need to release a new version because this is bad regression but easy fixable.

Thank you for your contribution and I will make new release ASAP.

[Proper-Job]

@vstoykov thank you

[matthewwithanm]

❤️

[vstoykov]

There is new release 4.0.1 in PyPi