Reduce the doctest lease duration...

[python_utils.git] / smart_future.py

diff --git a/smart_future.py b/smart_future.py
index 8f23e7756b5417b15d89ba35c43dde971678ee14..625c3ed66b63b3ec17e5dc94897a3ca1a88a5451 100644 (file)
--- a/smart_future.py
+++ b/smart_future.py
@@ -1,57 +1,131 @@
 #!/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
-from typing import Callable, List, TypeVar
+import logging
+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__)
 
 T = TypeVar('T')
 
 
-def wait_any(futures: List[SmartFuture], *, callback: Callable = None):
+def wait_any(
+    futures: List[SmartFuture],
+    *,
+    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()
-    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:
+        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)
-            yield smart_future_by_real_future[f]
     if callback is not None:
         callback()
-    return
 
 
-def wait_all(futures: List[SmartFuture]) -> None:
-    real_futures = [x.wrapped_future for x in futures]
+def wait_all(
+    futures: List[SmartFuture],
+    *,
+    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)
+        real_futures.append(x.wrapped_future)
+
     (done, not_done) = concurrent.futures.wait(
         real_futures, timeout=None, return_when=concurrent.futures.ALL_COMPLETED
     )
+    if log_exceptions:
+        for f in real_futures:
+            if 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
     assert len(done) == len(real_futures)
     assert len(not_done) == 0
 
 
 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")
 
@@ -64,5 +138,5 @@ class SmartFuture(DeferredOperand):
     # 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)