[Python-checkins] cpython (3.4): asyncio doc: update debug traces

[victor.stinner]

https://hg.python.org/cpython/rev/1f649b8cf69a
changeset: 93013:1f649b8cf69a
branch: 3.4
user: Victor Stinner <victor.stinner at gmail.com>
date: Sun Oct 12 21:37:16 2014 +0200
summary:
asyncio doc: update debug traces

files:
Doc/library/asyncio-dev.rst | 47 +++++++++++++++---------
1 files changed, 29 insertions(+), 18 deletions(-)


diff --git a/Doc/library/asyncio-dev.rst b/Doc/library/asyncio-dev.rst
--- a/Doc/library/asyncio-dev.rst
+++ b/Doc/library/asyncio-dev.rst
@@ -166,25 +166,34 @@
Output::

Task exception was never retrieved
- future: <Task finished bug() done at asyncio/coroutines.py:139 exception=Exception('not consumed',)>
- source_traceback: Object created at (most recent call last):
- File "test.py", line 10, in <module>
- asyncio.async(bug())
- File "asyncio/tasks.py", line 510, in async
- task = loop.create_task(coro_or_future)
+ future: <Task finished coro=<coro() done, defined at asyncio/coroutines.py:139> exception=Exception('not consumed',)>
Traceback (most recent call last):
- File "asyncio/tasks.py", line 244, in _step
+ File "asyncio/tasks.py", line 237, in _step
result = next(coro)
- File "coroutines.py", line 78, in __next__
- return next(self.gen)
File "asyncio/coroutines.py", line 141, in coro
res = func(*args, **kw)
- File "test.py", line 7, in bug
+ File "test.py", line 5, in bug
raise Exception("not consumed")
Exception: not consumed

:ref:`Enable the debug mode of asyncio <asyncio-debug-mode>` to get the
-traceback where the task was created.
+traceback where the task was created. Output in debug mode::
+
+ Task exception was never retrieved
+ future: <Task finished coro=<bug() done, defined at test.py:3> exception=Exception('not consumed',) created at test.py:8>
+ source_traceback: Object created at (most recent call last):
+ File "test.py", line 8, in <module>
+ asyncio.async(bug())
+ Traceback (most recent call last):
+ File "asyncio/tasks.py", line 237, in _step
+ result = next(coro)
+ File "asyncio/coroutines.py", line 79, in __next__
+ return next(self.gen)
+ File "asyncio/coroutines.py", line 141, in coro
+ res = func(*args, **kw)
+ File "test.py", line 5, in bug
+ raise Exception("not consumed")
+ Exception: not consumed

There are different options to fix this issue. The first option is to chain to
coroutine in another coroutine and use classic try/except::
@@ -303,15 +312,17 @@
Example of log::

Task was destroyed but it is pending!
- source_traceback: Object created at (most recent call last):
- File "test.py", line 17, in <module>
- task = asyncio.async(coro, loop=loop)
- File "asyncio/tasks.py", line 510, in async
- task = loop.create_task(coro_or_future)
- task: <Task pending kill_me() done at test.py:5 wait_for=<Future pending cb=[Task._wakeup()]>>
+ task: <Task pending coro=<kill_me() done, defined at test.py:5> wait_for=<Future pending cb=[Task._wakeup()]>>

:ref:`Enable the debug mode of asyncio <asyncio-debug-mode>` to get the
-traceback where the task was created.
+traceback where the task was created. Example of log in debug mode::
+
+ Task was destroyed but it is pending!
+ source_traceback: Object created at (most recent call last):
+ File "test.py", line 15, in <module>
+ task = asyncio.async(coro, loop=loop)
+ task: <Task pending coro=<kill_me() done, defined at test.py:5> wait_for=<Future pending cb=[Task._wakeup()] created at test.py:7> created at test.py:15>
+

.. seealso::