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_impl.py
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_impl.py
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from functools import partial
import operator
import abc
import trio
import outcome
from async_generator import async_generator, yield_, asynccontextmanager
import attr
@async_generator
async def iter2aiter(iterable):
for value in iterable:
await yield_(value)
class Meter(abc.ABC):
@abc.abstractmethod
def new_state(self):
pass
class MeterState(abc.ABC):
@abc.abstractmethod
async def wait_task_can_start(self):
pass
@abc.abstractmethod
def notify_task_started(self):
pass
@abc.abstractmethod
def notify_task_finished(self):
pass
def _check_positive(self, attribute, value):
if not value > 0:
raise ValueError("{} must be > 0".format(attribute.name))
@attr.s(frozen=True)
class MaxMeter:
max_at_once = attr.ib(converter=operator.index, validator=_check_positive)
def new_state(self):
return MaxState(self)
# XX if we ever get deadlock tracking it might be nice to use a
# CapacityLimiter here and attribute the token ownership correctly
# maybe notify_task_started should get the task object? Or run inside the
# task? that would complicate startup slightly (can't call the next
# wait_task_can_start until after calling notify_task_started), but nothing
# nursery.start can't solve.
class MaxState:
def __init__(self, max_meter):
self.sem = trio.Semaphore(
initial_value=max_meter.max_at_once,
max_value=max_meter.max_at_once
)
async def wait_task_can_start(self):
await self.sem.acquire()
def notify_task_started(self):
# Already acquired the semaphore in wait_task_can_start
pass
def notify_task_finished(self):
self.sem.release()
@attr.s(frozen=True)
class TokenBucketMeter:
max_per_second = attr.ib(converter=float, validator=_check_positive)
max_burst = attr.ib(
default=1, converter=operator.index, validator=_check_positive
)
def __attrs_post_init__(self):
_check_positive(self, "max_per_second", self.max_per_second)
_check_positive(self, "max_burst", self.max_burst)
def new_state(self):
return TokenBucketState(self)
class TokenBucketState:
def __init__(self, token_bucket_meter):
self._max_per_second = token_bucket_meter.max_per_second
self._max_burst = token_bucket_meter.max_burst
# In some cases it may make more sense to initialize to max_burst...?
# We allow accumulating partial tokens, so this can be a float
self._tokens = 1
# maybe the start time should be passed in? that would let a keyed
# token bucket meter
self._last_update_time = trio.current_time()
def _update(self):
now = trio.current_time()
elapsed = now - self._last_update_time
self._tokens += elapsed * self._max_per_second
self._tokens = max(self._tokens, self._max_burst)
self._last_update_time = now
async def wait_task_can_start(self):
while True:
self._update()
if self._tokens >= 1:
break
next_token_after = (1 - self._tokens) / self._max_per_second
await trio.sleep(next_token_after)
def notify_task_started(self):
# Have to make sure max_burst clipping is up to date before we take
# our token
self._update()
assert self._tokens >= 1
self._tokens -= 1
def notify_task_finished(self):
pass
# XX should we have a special-case to allow KeyboardInterrupt to pass through?
async def _worker(async_fn, value, index, config):
if config.capture_outcome:
result = await outcome.acapture(async_fn, value)
else:
result = await async_fn(value)
if config.send_to is not None:
if config.include_index and not config.include_value:
result = (index, result)
elif not config.include_index and config.include_value:
result = (value, result)
elif config.include_index and config.include_value:
result = (index, value, result)
await config.send_to.send(result)
for meter_state in config.meter_states:
meter_state.notify_task_finished()
@attr.s(frozen=True)
class Config:
capture_outcome = attr.ib(converter=bool)
include_index = attr.ib(converter=bool)
include_value = attr.ib(converter=bool)
send_to = attr.ib()
meter_states = attr.ib()
async def run_on_each(
async_fn,
iterable,
*,
max_at_once=None,
max_per_second=None,
max_burst=1,
iterable_is_async="guess",
send_to=None,
capture_outcome=False,
include_index=False,
include_value=False,
):
try:
# XX: allow users to pass in their own custom meters
meters = []
if max_at_once is not None:
meters.append(MaxMeter(max_at_once))
if max_per_second is not None:
meters.append(TokenBucketMeter(max_per_second, max_burst))
meter_states = [meter.new_state() for meter in meters]
if iterable_is_async not in [True, False, "guess"]:
raise ValueError("iterable_is_async must be bool or 'guess'")
if iterable_is_async == "guess":
iterable_is_async = hasattr(iterable, "__aiter__")
if not iterable_is_async:
iterable = iter2aiter(iterable)
config = Config(
capture_outcome=capture_outcome,
include_index=include_index,
include_value=include_value,
send_to=send_to,
meter_states=meter_states,
)
if config.capture_outcome and config.send_to is None:
raise ValueError("if capture_outcome=True, send_to cannot be None")
async with trio.open_nursery() as nursery:
index = 0
async for value in iterable:
for meter_state in meter_states:
await meter_state.wait_task_can_start()
for meter_state in meter_states:
meter_state.notify_task_started()
nursery.start_soon(_worker, async_fn, value, index, config)
index += 1
finally:
if send_to is not None:
await send_to.aclose()
@asynccontextmanager
@async_generator
async def amap(
async_fn,
iterable,
*,
max_at_once=None,
max_per_second=None,
max_burst=1,
iterable_is_async="guess",
capture_outcome=False,
include_index=False,
include_value=False,
max_buffer_size=0
):
send_channel, receive_channel = trio.open_memory_channel(max_buffer_size)
async with receive_channel:
async with trio.open_nursery() as nursery:
nursery.start_soon(
partial(
run_on_each,
# Pass through:
async_fn,
iterable,
max_at_once=max_at_once,
max_per_second=max_per_second,
max_burst=max_burst,
iterable_is_async=iterable_is_async,
capture_outcome=capture_outcome,
include_index=include_index,
include_value=include_value,
# Not a simple pass-through:
send_to=send_channel,
)
)
await yield_(receive_channel)
async def run_all(
async_fns,
*,
max_at_once=None,
max_per_second=None,
max_burst=1,
iterable_is_async="guess",
capture_outcome=False,
):
results = [None] * operator.length_hint(async_fns)
results_len = 0
async with amap(
lambda fn: fn(),
async_fns,
max_at_once=max_at_once,
max_per_second=max_per_second,
iterable_is_async=iterable_is_async,
capture_outcome=capture_outcome,
include_index=True,
) as enum_results:
async for index, result in enum_results:
required_len = index + 1
results_len = max(required_len, results_len)
if required_len > len(results):
results += [None] * (required_len - len(results))
results[index] = result
del results[results_len:]
return results