Source code for paco.throttle

# -*- coding: utf-8 -*-
import time
import asyncio
from .decorator import decorate
from .assertions import assert_corofunction

def now():
    Returns the current machine time in milliseconds.
    return int(round(time.time() * 1000))

[docs]@decorate def throttle(coro, limit=1, timeframe=1, return_value=None, raise_exception=False): """ Creates a throttled coroutine function that only invokes ``coro`` at most once per every time frame of seconds or milliseconds. Provide options to indicate whether func should be invoked on the leading and/or trailing edge of the wait timeout. Subsequent calls to the throttled coroutine return the result of the last coroutine invocation. This function can be used as decorator. Arguments: coro (coroutinefunction): coroutine function to wrap with throttle strategy. limit (int): number of coroutine allowed execution in the given time frame. timeframe (int|float): throttle limit time frame in seconds. return_value (mixed): optional return if the throttle limit is reached. Returns the latest returned value by default. raise_exception (bool): raise exception if throttle limit is reached. Raises: RuntimeError: if cannot throttle limit reached (optional). Returns: coroutinefunction Usage:: async def mul_2(num): return num * 2 # Use as simple wrapper throttled = paco.throttle(mul_2, limit=1, timeframe=2) await throttled(2) # => 4 await throttled(3) # ignored! # => 4 await asyncio.sleep(2) await throttled(3) # executed! # => 6 # Use as decorator @paco.throttle(limit=1, timeframe=2) async def mul_2(num): return num * 2 await mul_2(2) # => 4 await mul_2(3) # ignored! # => 4 await asyncio.sleep(2) await mul_2(3) # executed! # => 6 """ assert_corofunction(coro=coro) # Store execution limits limit = max(int(limit), 1) remaning = limit # Turn seconds in milliseconds timeframe = timeframe * 1000 # Keep call state last_call = now() # Cache latest retuned result result = None def stop(): if raise_exception: raise RuntimeError('paco: coroutine throttle limit exceeded') if return_value: return return_value return result def elapsed(): return now() - last_call @asyncio.coroutine def wrapper(*args, **kw): nonlocal result nonlocal remaning nonlocal last_call if elapsed() > timeframe: # Reset reamining calls counter remaning = limit # Update last call time last_call = now() elif elapsed() < timeframe and remaning <= 0: return stop() # Decrease remaining limit remaning -= 1 # Schedule coroutine passing arguments and cache result result = yield from coro(*args, **kw) return result return wrapper