def pick_recruiter(self):
"""Pick the next recruiter to use.
We use the `Recruitment` table in the db to keep track of
how many recruitments have been requested using each recruiter.
We'll use the first one from the specification that
hasn't already reached its quota.
"""
counts = dict(
session.query(Recruitment.recruiter_id, func.count(
Recruitment.id)).group_by(Recruitment.recruiter_id).all())
for recruiter_id, target_count in self.spec:
count = counts.get(recruiter_id, 0)
if count >= target_count:
# This recruiter quota was reached;
# move on to the next one.
counts[recruiter_id] = count - target_count
continue
else:
# Quota is still available; let's use it.
break
else:
raise Exception('Reached quota for all recruiters. '
'Not sure which one to use now.')
# record the recruitment
session.add(Recruitment(recruiter_id=recruiter_id))
# return an instance of the recruiter
return by_name(recruiter_id)
def recruiters(self, n=1):
"""Iterator that provides recruiters along with the participant
count to be recruited for up to `n` participants.
We use the `Recruitment` table in the db to keep track of
how many recruitments have been requested using each recruiter.
We'll use the first one from the specification that
hasn't already reached its quota.
"""
recruit_count = 0
while recruit_count <= n:
counts = dict(
session.query(Recruitment.recruiter_id,
func.count(Recruitment.id)).group_by(
Recruitment.recruiter_id).all())
for recruiter_id, target_count in self.spec:
remaining = 0
count = counts.get(recruiter_id, 0)
if count >= target_count:
# This recruiter quota was reached;
# move on to the next one.
counts[recruiter_id] = count - target_count
continue
else:
# Quota is still available; let's use it.
remaining = target_count - count
break
else:
return
num_recruits = min(n - recruit_count, remaining)
# record the recruitments and commit
for i in range(num_recruits):
session.add(Recruitment(recruiter_id=recruiter_id))
session.commit()
recruit_count += num_recruits
yield by_name(recruiter_id), num_recruits