python / python/cpython

Items put on Queue in thread in child process sometimes not seen by parent process

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stdlib topic-multiprocessing type-bug
Dominant language
Python
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Description

BPO 41614
Nosy @alexmojaki
Files
  • queue_bug.py: A script you can run to observe this bug, with extensive comments
  • 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 = None
    created_at = <Date 2020-08-22.11:42:15.115>
    labels = ['3.7', '3.8', '3.10']
    title = 'Items put on Queue in thread in child process sometimes not seen by parent process'
    updated_at = <Date 2020-08-22.11:42:15.115>
    user = 'https://github.com/alexmojaki'
    

    bugs.python.org fields:

    activity = <Date 2020-08-22.11:42:15.115>
    actor = 'alexmojaki'
    assignee = 'none'
    closed = False
    closed_date = None
    closer = None
    components = []
    creation = <Date 2020-08-22.11:42:15.115>
    creator = 'alexmojaki'
    dependencies = []
    files = ['49422']
    hgrepos = []
    issue_num = 41614
    keywords = []
    message_count = 1.0
    messages = ['375795']
    nosy_count = 1.0
    nosy_names = ['alexmojaki']
    pr_nums = []
    priority = 'normal'
    resolution = None
    stage = None
    status = 'open'
    superseder = None
    type = None
    url = 'https://bugs.python.org/issue41614'
    versions = ['Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.10']
    

    Contributor guide

    Open the contributing guide

    First steps

    1. Read the whole issue, then the project's contributing guide.
    2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
    3. Fork the repository and make your change on a branch.
    4. Open a pull request that references the issue number.

    Research direction

    Start by running queue_bug.py, the supplied reproduction script, and follow its extensive comments to observe when items placed on a Queue from a child-process thread are missing in the parent. Trace the relevant multiprocessing queue behavior and establish a regression test for the reported case; done means the parent reliably sees queued items. No test file is named in the issue.

    Written by the indexing model from the issue text.

    Assessment

    Tech stack
    python
    Domain
    operating-systems
    Issue type
    Bug
    Difficulty
    4/5
    Estimated time
    3-5 days
    Activity status
    Stale
    Clarity
    Mostly clear
    Newbie friendliness
    28/100

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