def _do(p: redis.client.Pipeline, number):
p.watch(number)
if p.get(number):
raise AlreadyExistException('Number already exists')
elif p.get(number + 1):
raise OneLessThatItWasException('Number is 1 less than required')
p.execute()
p.unwatch()
p.set(number, 'True')
p.execute()
def cache_helper(
pipeline: redis.client.Pipeline,
cache_key: str,
cache_func: Callable[..., Any],
cache_args: ArgsType = None,
cache_kwargs: KwargsType = None,
):
if cache_args is None:
cache_args = tuple()
if cache_kwargs is None:
cache_kwargs = dict()
# FIXME: there's a possible race condition in caching
# if cache is reset at the moment the round is updated,
# we could override the correct cache state with the state
# of the previous round if caching is started earlier
was_changed = False
while True:
try:
pipeline.watch(cache_key)
cached = pipeline.exists(cache_key)
pipeline.multi()
if not cached:
was_changed = True
cache_func(*cache_args, **cache_kwargs)
pipeline.execute()
except redis.WatchError:
time.sleep(0.05)
else:
break
return was_changed
def transaction_func(pipeline: redis.client.Pipeline) -> None:
pipeline.multi()
pipeline.set('my_pet', 'cat')
pipeline.set('my_pet', 'tiger')
pipeline.execute()