src/experiments/middleware.py

   1 import hashlib
   2 from django.conf import settings
   3
   4
   5 def experiments_middleware(get_response):
   6     def middleware(request):
   7         exps = {}
   8
   9         overrides = getattr(settings, 'EXPERIMENTS_OVERRIDES', {})
  10         for exp in settings.EXPERIMENTS:
  11             slug = exp['slug']
  12             if slug in overrides:
  13                 exps[slug] = overrides[slug]
  14                 continue
  15
  16             cookie_value = request.COOKIES.get(f'EXPERIMENT_{slug}')
  17             if cookie_value is not None:
  18                 for cohort in exp.get('cohorts', []):
  19                     if cohort['value'] == cookie_value:
  20                         exps[slug] = cookie_value
  21                         break
  22
  23             if slug not in exps:
  24                 number = int(
  25                     # TODO sth else?
  26                     hashlib.md5(
  27                         (slug + request.META['REMOTE_ADDR']).encode('utf-8')
  28                     ).hexdigest(),
  29                     16
  30                 ) % 10e6 / 10e6
  31                 for cohort in exp.get('cohorts', []):
  32                     number -= cohort.get('size', 1)
  33                     if number < 0:
  34                         exps[slug] = cohort['value']
  35                         break
  36
  37         request.EXPERIMENTS = exps
  38         response = get_response(request)
  39         return response
  40
  41     return middleware