Source code for

import asyncio
from typing import AsyncIterator, Iterator, Optional, Union

from jina.helper import get_or_reuse_loop

class _RequestsCounter:
    """Class used to wrap a count integer so that it can be updated inside methods.

    .. code-block:: python

        def count_increment(i: int, rc: _RequestsCounter):
            i += 1
            rc.count += 1

        c_int = 0
        c_rc = _RequestsCounter()
        count_increment(c_int, c_rc)

        assert c_int == 0
        assert c_rc.count == 1

    count = 0

[docs]class AsyncRequestsIterator: """Iterator to allow async iteration of blocking/non-blocking iterator from the Client""" def __init__( self, iterator: Union[Iterator, AsyncIterator], request_counter: Optional[_RequestsCounter] = None, prefetch: int = 0, ) -> None: """Async request iterator :param iterator: request iterator :param request_counter: counter of the numbers of request being handled at a given moment :param prefetch: The max amount of requests to be handled at a given moment (0 disables feature) """ self.iterator = iterator self._request_counter = request_counter self._prefetch = prefetch
[docs] def iterator__next__(self): """ Executed inside a `ThreadPoolExecutor` via `loop.run_in_executor` to avoid following exception. "StopIteration interacts badly with generators and cannot be raised into a Future" :return: next request or None """ try: return self.iterator.__next__() except StopIteration: return None
def __aiter__(self): return self async def __anext__(self): if isinstance(self.iterator, Iterator): """ An `Iterator` indicates "blocking" code, which might block all tasks in the event loop. Hence we iterate in the default executor provided by asyncio. """ request = await get_or_reuse_loop().run_in_executor( None, self.iterator__next__ ) """ `iterator.__next__` can be executed directly and that'd raise `StopIteration` in the executor, which raises the following exception while chaining states in futures. "StopIteration interacts badly with generators and cannot be raised into a Future" To avoid that, we handle the raise by a `return None` """ if request is None: raise StopAsyncIteration elif isinstance(self.iterator, AsyncIterator): # we assume that `AsyncIterator` doesn't block the event loop request = await self.iterator.__anext__() if self._prefetch > 0: while self._request_counter.count >= self._prefetch: await asyncio.sleep(0) return request