egg and modpython

[Paul Boddie]

Bruno Desthuilliers wrote:
> Wensheng a écrit :
> > I installed pysqlite2 using easy_install.
> > and got this when using it from modpython:
> > --------------------------------------------------------------------------------------------------
> > Mod_python error: "PythonHandler etc.modpython"

[...]

I applaud you for studying the traceback in more depth than I can find
the motivation for, Bruno. ;-) However, this looks like a program using
some package installed by setuptools/easy_install needs to unpack that
package when running.

> > ExtractionError: Can't extract file(s) to egg cache
>
> > The following error occurred while trying to extract file(s) to the
> > Python egg cache:
>
> >   [Errno 13] Permission denied: '/var/www/.python-eggs'

And this wants to happen apparently in the home directory of the Web
server user, whose rights may be somewhat limited. Or perhaps one has
to initialise setuptools for any particular user by running it first as
that user: something that isn't a particularly common thing to do with
non-interactive users on UNIX-like systems.

[...]

> > Can peak developers fix this please?
>
> Why should they "fix" something that's
> 1/ documented
>     -> http://peak.telecommunity.com/DevCenter/EggFormats#zip-file-issues

"The Internal Structure of Python Eggs / STOP! This is not the first
document you should read!" A case of "Beware of the Leopard" perhaps?

> 2/ not a an egg specific issue

In my experience, most other package managers actually unpack their
resources when invoked, rather than leaving the programs to attempt
such things when running. Debian packages even compile the bytecode
files to ensure that nothing tries (and fails) to write them to
privileged locations afterwards.

> 3/ really just a configuration/permission problem

Which should have been solved when the package manager was invoked,
especially since this was most likely done as root.

[...]

> > in the mean time, I just have to use old "download, unzip/untar &&
> > python setup.py install" way.
>
> No - you have to read the manual and fix you configuration. FWIW, the
> above traceback gives far enough clues (it's even written in all letters).

The various ways to deal with this include running easy_install as the
Web server user so that it can touch the directory and whatever else it
needs, and perhaps to set up various permissions - something you
wouldn't usually do; running easy_install with the --always-unzip flag
when installing the package as root; using python setup.py install as
usual.

This situation looks either a lot like a use case whose popularity has
been underestimated by the developers - intriguing given the number of
people supposedly using setuptools for their Web application
deployments - or a packaging mistake with the pysqlite2 .egg file.
Either way, system packages rarely suffer from this kind of problem,
and it's quite understandable (and justifiable) to consider this bad
behaviour.

> Or you may read easy_install's doc to avoid installing zipped eggs:
> http://peak.telecommunity.com/DevCenter/EasyInstall#compressed-installation

Perhaps the developers should reverse their defaults and emulate the
usual behaviour of package managers, unfashionable as that may seem.

Paul