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asyncio.all_tasks() should return only non-finished tasks. #76791

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asvetlov opened this issue Jan 21, 2018 · 7 comments
Closed

asyncio.all_tasks() should return only non-finished tasks. #76791

asvetlov opened this issue Jan 21, 2018 · 7 comments
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3.8 only security fixes release-blocker topic-asyncio

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@asvetlov
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BPO 32610
Nosy @asvetlov, @1st1, @miss-islington
PRs
  • bpo-32610: Fix asyncio.all_tasks() to return only pending tasks. #7174
  • [3.7] bpo-32610: Fix asyncio.all_tasks() to return only pending tasks. (GH-7174) #7181
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    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = None
closed_at = <Date 2018-05-29.15:16:15.087>
created_at = <Date 2018-01-21.16:45:25.597>
labels = ['release-blocker', '3.8', 'expert-asyncio']
title = 'asyncio.all_tasks() should return only non-finished tasks.'
updated_at = <Date 2018-05-29.15:16:15.086>
user = 'https://github.com/asvetlov'

    bugs.python.org fields:

    activity = <Date 2018-05-29.15:16:15.086>
actor = 'yselivanov'
assignee = 'none'
closed = True
closed_date = <Date 2018-05-29.15:16:15.087>
closer = 'yselivanov'
components = ['asyncio']
creation = <Date 2018-01-21.16:45:25.597>
creator = 'asvetlov'
dependencies = []
files = []
hgrepos = []
issue_num = 32610
keywords = ['patch']
message_count = 7.0
messages = ['310378', '310379', '312907', '317921', '317927', '317928', '317963']
nosy_count = 3.0
nosy_names = ['asvetlov', 'yselivanov', 'miss-islington']
pr_nums = ['7174', '7181']
priority = 'release blocker'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue32610'
versions = ['Python 3.8']
    @asvetlov
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    Current behavior has a subtle pitfall.
    The function returns a list of *existing* tasks (not removed by decref or explicit call).
    If user's code has a strong reference to some task the task will be in return list for unpredictable amount of time, even if the task was done.

    Returning only alive tasks can make a function result more predictable (not task.done()).

    Opinions?

    @1st1
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    1st1 commented Jan 21, 2018

    I agree, returning done tasks is pretty useless.

    This is a new function so let's fix its behavour. We need to:

    1. Document this difference between new asyncio.all_tasks() and now deprecated Task.all_tasks().

    2. Make sure that Task.all_tasks() works in 3.7 in the same way it was working before 3.7.

    @asvetlov
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    After re-thinking I come to another idea: let's keep all_tasks() behavior as is but add an active_tasks() function for returning all non-finished tasks.

    It should be done in Python 3.8

    @asvetlov asvetlov added 3.8 only security fixes and removed 3.7 (EOL) end of life labels Feb 26, 2018
    @1st1
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    1st1 commented May 28, 2018

    After an off-list discussion I think I was able to convince Andrew to change the behaviour of the newly added asyncio.all_tasks() to return only pending tasks. The logic behind this is that:

    1. there's no good known use case for returning a list of all non-GC-ed tasks; if such a case exists, it's easy to implement support for it via 'loop.set_task_factory'.

    2. OTOH, whenever one uses Task.all_task() they always want to filter out completed tasks.

    3. Since this is a new API, it makes sense to design it right and not strive for backwards compatibility with now deprecated asyncio.Task.all_tasks().

    @1st1
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    1st1 commented May 28, 2018

    New changeset 416c1eb by Yury Selivanov in branch 'master':
    bpo-32610: Fix asyncio.all_tasks() to return only pending tasks. (GH-7174)
    416c1eb

    @1st1
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    1st1 commented May 28, 2018

    Ned, this one would also be nice to have in 3.7.0. The patch alters the behaviour of new 3.7 api.

    @miss-islington
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    New changeset ddc613f by Miss Islington (bot) in branch '3.7':
    bpo-32610: Fix asyncio.all_tasks() to return only pending tasks. (GH-7174)
    ddc613f

    @1st1 1st1 closed this as completed May 29, 2018
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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