#!/usr/bin/env python3
+# © Copyright 2021-2022, Scott Gasch
+
+"""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
-import traceback
-from typing import Callable, List, TypeVar
+from typing import Callable, List, Set, TypeVar
from overrides import overrides
+import id_generator
+
# This module is commonly used by others in here and should avoid
# taking any unnecessary dependencies back on them.
from deferred_operand import DeferredOperand
-import id_generator
logger = logging.getLogger(__name__)
callback: Callable = None,
log_exceptions: bool = True,
):
+ """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?
+ """
+
real_futures = []
smart_future_by_real_future = {}
- completed_futures = set()
- for _ in futures:
- real_futures.append(_.wrapped_future)
- smart_future_by_real_future[_.wrapped_future] = _
+ completed_futures: Set[fut.Future] = set()
+ for x in futures:
+ assert isinstance(x, SmartFuture)
+ real_futures.append(x.wrapped_future)
+ 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:
if log_exceptions and not f.cancelled():
exception = f.exception()
if exception is not None:
- logger.warning(
- f'Future {id(f)} raised an unhandled exception and exited.'
- )
+ 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()
- return
def wait_all(
*,
log_exceptions: bool = True,
) -> None:
- real_futures = [x.wrapped_future for x in futures]
+ """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)
+ real_futures.append(x.wrapped_future)
+
(done, not_done) = concurrent.futures.wait(
real_futures, timeout=None, return_when=concurrent.futures.ALL_COMPLETED
)
if not f.cancelled():
exception = f.exception()
if exception is not None:
- logger.warning(
- f'Future {id(f)} raised an unhandled exception and exited.'
- )
+ logger.warning('Future 0x%x raised an unhandled exception and exited.', id(f))
logger.exception(exception)
raise exception
assert len(done) == len(real_futures)
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.
"""
def __init__(self, wrapped_future: fut.Future) -> None:
+ assert isinstance(wrapped_future, fut.Future)
self.wrapped_future = wrapped_future
self.id = id_generator.get("smart_future_id")
# You shouldn't have to call this; instead, have a look at defining a
# method on DeferredOperand base class.
@overrides
- def _resolve(self, *, timeout=None) -> T:
+ def _resolve(self, timeout=None) -> T:
return self.wrapped_future.result(timeout)