python / python/cpython

Email header with ;;;; stuffing takes very long to parse

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3.12 performance topic-email
Dominant language
Python
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Description

BPO 42909
Nosy @warsaw, @bitdancer, @akulakov, @eriker-fsc
Files
  • repro.py: Simple self-contained repro script - should take less than 1s but takes more than 30
  • 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 2021-01-12.13:13:10.953>
    labels = ['3.8', 'expert-email', '3.10', 'performance', '3.7', '3.9']
    title = 'Email header with ;;;; stuffing takes very long to parse'
    updated_at = <Date 2021-07-09.22:18:24.963>
    user = 'https://github.com/eriker-fsc'
    

    bugs.python.org fields:

    activity = <Date 2021-07-09.22:18:24.963>
    actor = 'andrei.avk'
    assignee = 'none'
    closed = False
    closed_date = None
    closer = None
    components = ['email']
    creation = <Date 2021-01-12.13:13:10.953>
    creator = 'eriker'
    dependencies = []
    files = ['49736']
    hgrepos = []
    issue_num = 42909
    keywords = []
    message_count = 3.0
    messages = ['384931', '384938', '397228']
    nosy_count = 4.0
    nosy_names = ['barry', 'r.david.murray', 'andrei.avk', 'eriker']
    pr_nums = []
    priority = 'normal'
    resolution = None
    stage = None
    status = 'open'
    superseder = None
    type = 'resource usage'
    url = 'https://bugs.python.org/issue42909'
    versions = ['Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.9', '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 with the linked repro.py script and run it to reproduce the email-header parsing slowdown. Trace the email component's parsing path to identify the cause, then verify that the repro completes in under one second and add or update a regression test if the relevant test location can be found.

    Written by the indexing model from the issue text.

    Assessment

    Tech stack
    python
    Domain
    performance
    Issue type
    Bug
    Difficulty
    4/5
    Estimated time
    3-5 days
    Activity status
    Stale
    Clarity
    Mostly clear
    Newbie friendliness
    35/100

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