When an asyncio.Task is cancelled, the exception traceback now
starts with where the task was first interrupted. Previously,
the traceback only had "depth one."
Currently, if asyncio.wait_for() timeout expires, it cancels
inner future and then always raises TimeoutError. In case
those future is task, it can handle cancelation mannually,
and those process can lead to some other exception. Current
implementation silently loses thoses exception.
To resolve this, wait_for will check was the cancelation
successfull or not. In case there was exception, wait_for
will reraise it.
Co-authored-by: Roman Skurikhin <roman.skurikhin@cruxlab.com>
This will address the common mistake many asyncio users make:
an "except Exception" clause breaking Tasks cancellation.
In addition to this change, we stop inheriting asyncio.TimeoutError
and asyncio.InvalidStateError from their concurrent.futures.*
counterparts. There's no point for these exceptions to share the
inheritance chain.
In 3.9 we'll focus on implementing supervisors and cancel scopes,
which should allow better handling of all exceptions, including
SystemExit and KeyboardInterrupt
When the future returned by shield is cancelled, its completion callback of the
inner future is not removed. This makes the callback list of inner inner future
grow each time a shield is created and cancelled.
This change unregisters the callback from the inner future when the outer
future is cancelled.
https://bugs.python.org/issue35125
* Insert the warn in the asyncio.sleep when the loop argument is used
* Insert the warn in the asyncio.wait and asyncio.wait_for when the loop argument is used
* Better format of the code
* Add news file
* change calls for get_event_loop() to calls for get_running_loop()
* Change message to be more clear in News
* Improve the comments in test_tasks
Currently, asyncio.wait_for(fut), upon reaching the timeout deadline,
cancels the future and returns immediately. This is problematic for
when *fut* is a Task, because it will be left running for an arbitrary
amount of time. This behavior is iself surprising and may lead to
related bugs such as the one described in bpo-33638:
condition = asyncio.Condition()
async with condition:
await asyncio.wait_for(condition.wait(), timeout=0.5)
Currently, instead of raising a TimeoutError, the above code will fail
with `RuntimeError: cannot wait on un-acquired lock`, because
`__aexit__` is reached _before_ `condition.wait()` finishes its
cancellation and re-acquires the condition lock.
To resolve this, make `wait_for` await for the task cancellation.
The tradeoff here is that the `timeout` promise may be broken if the
task decides to handle its cancellation in a slow way. This represents
a behavior change and should probably not be back-patched to 3.6 and
earlier.
Fix the following bugs in the C implementation:
* get_future_loop() silenced all exceptions raised when look up the get_loop
attribute, not just an AttributeError.
* enter_task() silenced all exceptions raised when look up the current task,
not just a KeyError.
* repr() was called for a borrowed link in enter_task() and task_step_impl().
* str() was used instead of repr() in formatting one error message (in
Python implementation too).
* There where few reference leaks in error cases.
Specifically, it's not possible to subclass Task/Future classes
and override the following methods:
* Future._schedule_callbacks
* Task._step
* Task._wakeup
* Convert asyncio/tasks.py to async/await
* Convert asyncio/queues.py to async/await
* Convert asyncio/test_utils.py to async/await
* Convert asyncio/base_subprocess.py to async/await
* Convert asyncio/subprocess.py to async/await
* Convert asyncio/streams.py to async/await
* Fix comments
* Convert asyncio/locks.py to async/await
* Convert asyncio.sleep to async def
* Add a comment
* Add missing news
* Convert stubs from AbstrctEventLoop to async functions
* Convert subprocess_shell/subprocess_exec
* Convert connect_read_pipe/connect_write_pip to async/await syntax
* Convert create_datagram_endpoint
* Convert create_unix_server/create_unix_connection
* Get rid of old style coroutines in unix_events.py
* Convert selector_events.py to async/await
* Convert wait_closed and create_connection
* Drop redundant line
* Convert base_events.py
* Code cleanup
* Drop redundant comments
* Fix indentation
* Add explicit tests for compatibility between old and new coroutines
* Convert windows event loop to use async/await
* Fix double awaiting of async function
* Convert asyncio/locks.py
* Improve docstring
* Convert tests to async/await
* Convert more tests
* Convert more tests
* Convert more tests
* Convert tests
* Improve test
The asyncio/compat.py file was written to support Python < 3.5 and
Python < 3.5.2. But Python 3.5 doesn't accept bugfixes anymore, only
security fixes. There is no more need to backport bugfixes to Python
3.5, and so no need to have a single code base for Python 3.5, 3.6
and 3.7.
Say hello (again) to "async" and "await", who became real keywords in
Python 3.7 ;-)
when there are no more `await` or `yield (from)` before return in coroutine,
cancel was ignored.
example:
async def coro():
asyncio.Task.current_task().cancel()
return 42
...
res = await coro() # should raise CancelledError
This implementation provides additional 10-20% speed boost for
asyncio programs.
The patch also fixes _asynciomodule.c to use Arguments Clinic, and
makes '_schedule_callbacks' an overridable method (as it was in 3.5).
This is now an official "protected" API that can be used to write
classes that are duck-type-compatible with Future without subclassing
it. (For that purpose I also changed isinstance(result, Future) to
check for this attribute instead.)
Hopefully Amber Brown can use this to make Twisted.Deferred compatible
with asyncio.Future.
Tests and docs are TBD.
* Fix ResourceWarning warnings in test_streams
* Return True from StreamReader.eof_received() to fix
http://bugs.python.org/issue24539 (but still needs a unittest).
Add StreamReader.__repr__() for easy debugging.
* remove unused imports
* Issue #234: Drop JoinableQueue on Python 3.5+
* Cleanup gather(): use cancelled() method instead of using private Future
attribute
* Fix _UnixReadPipeTransport and _UnixWritePipeTransport. Only start reading
when connection_made() has been called.
* Issue #23333: Fix BaseSelectorEventLoop._accept_connection(). Close the
transport on error. In debug mode, log errors using call_exception_handler()
* Document why set_result() calls are safe
* Cleanup gather(). Use public methods instead of hacks to consume the
exception of a future.
* sock_connect(): pass directly the fd to _sock_connect_done instead of the
socket.
Don't raise a TimeoutError if we reached the timeout and the future completed
in the same iteration of the event loop. A side effect of the bug is that
Queue.get() looses items.
* _WaitHandleFuture.cancel() now notify IocpProactor through the overlapped
object that the wait was cancelled.
* Optimize IocpProactor.wait_for_handle() gets the result if the wait is
signaled immediatly.
* Enhance representation of Future and Future subclasses
- Add "created at filename:lineno" in the representation
- Add Future._repr_info() method which can be more easily overriden than
Future.__repr__(). It should now be more easy to enhance Future
representation without having to modify each subclass. For example,
_OverlappedFuture and _WaitHandleFuture get the new "created at" information.
- Use reprlib to format Future result, and function arguments when formatting a
callback, to limit the length of the representation.
* Fix repr(_WaitHandleFuture)
* _WaitHandleFuture and _OverlappedFuture: hide frames of internal calls in the
source traceback.
* Cleanup ProactorIocp._poll(): set the timeout to 0 after the first call to
GetQueuedCompletionStatus()
* test_locks: close the temporary event loop and check the condition lock
* Remove workaround in test_futures, no more needed
* Tulip issue #182: Improve logs of BaseEventLoop._run_once()
- Don't log non-blocking poll
- Only log polling with a timeout if it gets events or if it timed out after
more than 1 second.
* Fix some pyflakes warnings: remove unused imports
- CoroWrapper.__del__() now reuses repr(CoroWrapper) to log the "... was never
yielded from" warning
- Improve CoroWrapper: copy also the qualified name on Python 3.4, not only on
Python 3.5+
- repr(Task) and repr(CoroWrapper) now also includes where these objects were
created. If the coroutine is not a generator (don't use "yield from"), use
the location of the function, not the location of the coro() wrapper.
- Fix create_task(): truncate the traceback to hide the call to create_task().
- Tulip issue 185: Add a create_task() method to event loops. The create_task()
method can be overriden in custom event loop to implement their own task
class. For example, greenio and Pulsar projects use their own task class. The
create_task() method is now preferred over creating directly task using the
Task class.
- tests: fix a warning
- fix typo in the name of a test function
- Update AbstractEventLoop: add new event loop methods; update also the unit test
* _UnixSubprocessTransport: fix file mode of stdin. Open stdin in write mode,
not in read mode
* Examples: close the event loop at exit
* More reliable CoroWrapper.__del__. If the constructor is interrupted by
KeyboardInterrupt or the coroutine objet is destroyed lately, some the
_source_traceback attribute doesn't exist anymore.
* repr(Task): include also the future the task is waiting for
Handle objects are created. Pass the traceback to call_exception_handler() in
the 'source_traceback' key.
The traceback is truncated to hide internal calls in asyncio, show only the
traceback from user code.
Add tests for the new source_traceback, and a test for the 'Future/Task
exception was never retrieved' log.
done: use the first line number of the code object instead of the current line
number of the generator frame.
The name of the coroutine is not enough because many coroutines may have the
same name. It's a common case in asyncio tests for example.
Python 3.5
- Drop __slots__ optimization of CoroWrapper to be able to set the __qualname__
attribute.
- Add tests on __name__, __qualname__ and __module__ of a coroutine function
and coroutine object.
- Fix test_tasks when run in debug mode (PYTHONASYNCIODEBUG env var set) on
Python 3.3 or 3.4
Chris Jerdonek
romasku
Kyle Stanley
Batuhan Taşkaya
Yury Selivanov
Andrew Svetlov
Alex Grönholm
Yury Selivanov
Matthias Bussonnier
Romain Picard
Zackery Spytz
gescheit
Inada Naoki
João Júnior
Elvis Pranskevichus
jimmylai
Serhiy Storchaka
Victor Stinner
Victor K
INADA Naoki
Charles Renwick
Mariatta Wijaya
Guido van Rossum
Yury Selivanov
R David Murray