On Sep 28, 2014, at 5:36 PM, M.-A. Lemburg <mal@egenix.com> wrote:

On 28.09.2014 21:31, Donald Stufft wrote:

Hello All!

I'd like to discuss the idea of moving PyPI to having immutable files. This
would mean that once you publish a particular file you can never reupload that
file again with different contents. This would still allow deleting the file or
reuploading it if the checksums match what was there prior.

This would be good for a few reasons:

* It represents "best practices" for version numbers. Ideally if two people
have version "2.1" of a project, they'll have the same code, however as it
stands two people installing at two different times could have two very
different versions.

* This will make improving the PyPI infrastructure easier, in particular it
will make it simpler to move away from using a glusterfs storage array and
switch to a redudant set of cloud object stores.

In the past this was brought up and a few points were brought against it, those
were:

1. That authors could simply change files that were hosted on not PyPI anyways
  so it didn't really do much.

2. That it was too hard to test a release prior to uploading it due to the
  nature of distutils requiring you to build the release in the same command
  as the upload.

With the fact that pip no longer hits external URLs by default, I believe that
the first item is no longer that large of a factor. People can do whatever they
want on external URLs of course, however if something is coming from PyPI as
end users should now be aware of, they can know it is immutable.

Now that there is twine, which allows uploading already created packages, I
also believe that the second item is no longer a concern. People can easily
create a distribution using ``setup.py sdist``, test it, and then upload that
exact thing they tested using ``twine upload <path to sdist>``.

-1.

It does happen that files need to be reuploaded because of a bug
in the release process and how people manage their code is really
*their* business, not that of PyPI.

Can you describe a reasonable hypothetical situation where this would occur

often enough as to be something that is likely to happen on a consistent

basis? Originally the problem was there was little ability to easily upload

pre-created files so there was a reasonable chance that there may be a

packaging bug that didn’t get exposed until you actually packaged + released.

With the advent of twine though it’s now possible to test the exact bits that

get uploaded to PyPI making that particular issue no longer a problem.

However, the fact that the files are not immutable *do* cause a number of

problems that need to be worked around in the mirroring infrastructure, the

CDN, and for scaling PyPI out and removing the glusterfs component.

FWIW, I am getting increasingly annoyed how PyPI and pip try to dictate
the way package authors are supposed to build, manage and host their
Python packages and release process. Can we please stop this ?