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A loose layout, venv-with-symlink PEX creates brittle symlinks #2023

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thejcannon opened this issue Jan 3, 2023 · 7 comments · Fixed by #2033
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A loose layout, venv-with-symlink PEX creates brittle symlinks #2023

thejcannon opened this issue Jan 3, 2023 · 7 comments · Fixed by #2033
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@thejcannon
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Pex version 2.1.113

I found this through Pants, but ultimately seems like a PEX issue/fix.

$ pex --no-venv-copies --layout=loose --venv prepend awscli --script aws -o  awscli.pex
$ python awscli.pex help
<help output>
$ mv awscli.pex awscli2.pex/
$ python awscli2.pex
Traceback (most recent call last):
  File "/home/josh/.pex/venvs/ea7cb7998ed2db4f784178989a4034013cd10e01/ddab8011daaee380698ac2fb9701af18c90c03f6/bin/aws", line 19, in <module>
    import awscli.clidriver
ModuleNotFoundError: No module named 'awscli

See also:

$ ls -l /home/josh/.pex/venvs/ea7cb7998ed2db4f784178989a4034013cd10e01/ddab8011daaee380698ac2fb9701af18c90c03f6/lib/python3.8/site-packages/awscli
lrwxrwxrwx 1 josh josh 107 Jan  3 11:49 /home/josh/.pex/venvs/ea7cb7998ed2db4f784178989a4034013cd10e01/ddab8011daaee380698ac2fb9701af18c90c03f6/lib/python3.8/site-packages/awscli -> ../../../../../../../../../<CWD>/awscli.pex/.deps/awscli-1.27.41-py3-none-any.whl/awscli

In Pants-land, this manifests as being a symlink to an ephemeral Pants sandbox which has since gone bye-bye.

What I might expect is that on first run, the wheels get copied into the PEX root and then the venv symlinks to the extracted wheels in the pex root so moving/deleting the original pex doesn't invalidate the venv.
@thejcannon thejcannon changed the title A loose layout, venv-with-symlink PEX creates birttle symlinks A loose layout, venv-with-symlink PEX creates brittle symlinks Jan 3, 2023
@jsirois
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jsirois commented Jan 3, 2023

Pants doesn't use loose, only packed. The same problem likely exists there though. Is loose use new or not a relevant / accurate detail here?

@thejcannon
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I'm declaring a pex_binary so the keys are all mine.

@thejcannon
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I also couldn't reproduce with packed or zipapp layouts, so I do think it is relevant.

@jsirois
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jsirois commented Jan 3, 2023

Gotcha. Thanks for the extra context.

Bug fix aside, if you're willing to share the use case, loose -> venv. Its supported and needs to be fixed, but also the oddest use case in the matrix of layouts x execution mode so I'm curious.

@thejcannon
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No specific use-case other than "was using loose, then tacked on venv". Our local fix is to drop the "loose".

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jsirois commented Jan 3, 2023

What was the loose for in the 1st place though? I am aware of 0 loose users (Pants would be if sandboxing were performant); so I'd love to learn what problems it helps people with.

@thejcannon
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The PR that introduced it lacks context 😒 If I had to guess it was either to workaround a bug or was a result of "bang on it until it works"

@jsirois jsirois added the bug label Jan 4, 2023
@jsirois jsirois self-assigned this Jan 9, 2023
@jsirois jsirois mentioned this issue Jan 9, 2023
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jsirois added a commit to jsirois/pex that referenced this issue Jan 9, 2023
@jsirois
Fix loose --venv PEXes to be robust to moves.
7a48fd9 
Both packed and zipped PEXes undergo an unzip into the PEX_ROOT prior to
any other action, establishing a known private cache of their contents.
Loose PEXes skip this step and run directly from their loose contents.
This is fine and speedy for the "zipapp" execution mode, but leads to an
incorrect venv cache in symlink mode where venv entries symlink back out
to the loose PEX and can thus be invalidated by moves outside Pex
control. Force loose PEXes in `--venv` mode to use copies so that their
cached venv is robust to external moves.

Fixes pex-tool#2023
@jsirois jsirois mentioned this issue Jan 9, 2023
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jsirois added a commit that referenced this issue Jan 10, 2023
@jsirois
Fix loose --venv PEXes to be robust to moves. (#2033)
f723302 
Both packed and zipped PEXes undergo an unzip into the PEX_ROOT prior to
any other action, establishing a known private cache of their contents.
Loose PEXes skip this step and run directly from their loose contents.
This is fine and speedy for the "zipapp" execution mode, but leads to an
incorrect venv cache in symlink mode where venv entries symlink back out
to the loose PEX and can thus be invalidated by moves outside Pex
control. Force loose PEXes in `--venv` mode to use copies so that their
cached venv is robust to external moves.

Fixes #2023
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Fix loose --venv PEXes to be robust to moves. jsirois/pex
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