#!/usr/bin/env python3
-"""A future that can be treated like the result that it contains and
-will not block until it is used. At that point, if the underlying
-value is not yet available, it will block until it becomes
-available."""
+# © Copyright 2021-2022, Scott Gasch
-from __future__ import annotations
+"""A :class:`Future` that can be treated as a substutute for the result
+that it contains and will not block until it is used. At that point,
+if the underlying value is not yet available yet, it will block until
+the internal result actually becomes available.
+"""
+from __future__ import annotations
import concurrent
import concurrent.futures as fut
import logging
*,
callback: Callable = None,
log_exceptions: bool = True,
+ timeout: float = None,
):
+ """Await the completion of any of a collection of SmartFutures and
+ invoke callback each time one completes, repeatedly, until they are
+ all finished.
+
+ Args:
+ futures: A collection of SmartFutures to wait on
+ callback: An optional callback to invoke whenever one of the
+ futures completes
+ log_exceptions: Should we log (warning + exception) any
+ underlying exceptions raised during future processing or
+ silently ignore then?
+ timeout: invoke callback with a periodicity of timeout while
+ awaiting futures
+ """
+
real_futures = []
smart_future_by_real_future = {}
completed_futures: Set[fut.Future] = set()
smart_future_by_real_future[x.wrapped_future] = x
while len(completed_futures) != len(real_futures):
- newly_completed_futures = concurrent.futures.as_completed(real_futures)
- for f in newly_completed_futures:
+ try:
+ newly_completed_futures = concurrent.futures.as_completed(real_futures, timeout=timeout)
+ for f in newly_completed_futures:
+ if callback is not None:
+ callback()
+ completed_futures.add(f)
+ if log_exceptions and not f.cancelled():
+ exception = f.exception()
+ if exception is not None:
+ logger.warning(
+ 'Future 0x%x raised an unhandled exception and exited.', id(f)
+ )
+ logger.exception(exception)
+ raise exception
+ yield smart_future_by_real_future[f]
+ except TimeoutError:
if callback is not None:
callback()
- completed_futures.add(f)
- if log_exceptions and not f.cancelled():
- exception = f.exception()
- if exception is not None:
- logger.warning('Future 0x%x raised an unhandled exception and exited.', id(f))
- logger.exception(exception)
- raise exception
- yield smart_future_by_real_future[f]
if callback is not None:
callback()
*,
log_exceptions: bool = True,
) -> None:
+ """Wait for all of the SmartFutures in the collection to finish before
+ returning.
+
+ Args:
+ futures: A collection of futures that we're waiting for
+ log_exceptions: Should we log (warning + exception) any
+ underlying exceptions raised during future processing or
+ silently ignore then?
+ """
+
real_futures = []
for x in futures:
assert isinstance(x, SmartFuture)
class SmartFuture(DeferredOperand):
- """This is a SmartFuture, a class that wraps a normal Future and can
- then be used, mostly, like a normal (non-Future) identifier.
+ """This is a SmartFuture, a class that wraps a normal :class:`Future`
+ and can then be used, mostly, like a normal (non-Future)
+ identifier of the type of that SmartFuture's result.
Using a FutureWrapper in expressions will block and wait until
the result of the deferred operation is known.