[Distutils] [tg-trunk] Re: [ANN] EggFreezer

[Ian Bicking]

Alberto Valverde wrote:
>> Alberto Valverde wrote:
>> [...]
>>>> No... which makes binary eggs unusable on Linux.  I feel like there was
>>>> something else that made binary packages on a Mac unreliable, but I
>>>> can't remember.  Windows binary eggs generally work fine.  This is
>>>> discussed some here:
>>>> http://philikon.wordpress.com/2008/06/26/is-there-a-point-to-distributing-egg-files/
>>>>
>>> I remember reading that... Perhaps a solution could be to"freeze" the
>>> tar.gzs too, beside the compiled eggs in case we're lucky,  and hope
>>> that a compiler + libs are there when the install script is thawed. If
>>> the compiled egg won't cut it, then try to compile form source. I'm not
>>> sure how to tell easy_install to download the source distributions
>>> though.
>> Well, it'll make eggs from your tarballs anyway.  Turning it into a
>> build process is a bit of a nuisance... I was hoping for something that
>> didn't require building, but just did installation.
> 
> Yes, installation is the primary concern. I was suggesting the possibility
> of bundling the source distributions of platform dependent eggs just in
> case  we can compile them by any chance if there's no pre-compiled binary
> available. Just like easy_install does when downloading from an index, ut
> without net access.

Probably we're both having the same problem, which is that we're using 
easy_install to download packages, but then of course it also installs 
the packages, which is almost okay so long as you are okay with an egg. 
  But if it just downloaded, that'd be better.  I'm sure some digging 
would reveal a way to just download.

>> That said, it might work.  Maybe PoachEggs (mentioned later) does what
>> you want in this case.  Or, maybe it can be slightly modified to do what
>> you want (I think it might also unintentionally turn tarballs into eggs).
> 
> I took a look at it as a source of ideas when experimenting with all this
> stuff. One reason I discarded it was because I was under the impression
> that you need to manually provide a requirements list and I wanted
> something as automatic as possible, which you could say "get me TG + all
> it's deps" and it'll use easy_install to satisfy those deps. for you.
> 
> However, no that I've looked at it more closely it seems that it can
> piggy-back on virtualenv to build this list, right?

It lets you be more specific about packages than setup.py, but it 
doesn't require you to enumerate everything.  If you install Pylons 
it'll pick up all of Pylons' requirements.

The idea of PoachEggs, though, is that often a second-level requirement 
effects the stability of an application.  So if you require 
Pylons==0.9.6, but Pylons doesn't require a specific version of Beaker, 
you might have problems when a newer version of Beaker appears. 
Relatedly, it's awkward to even put a requirement like Pylons==0.9.6 in 
your application, and you may not know one way or the other if Pylons 
0.9.7 would work.

So PoachEggs just lets you put all these requirements in a separate 
file, outside of any setup.py.  You can also get a working environment, 
and then "freeze" the requirements to a set of exact versions of 
packages.  It's equivalent to what people are doing with custom package 
indexes.

>> I have thought about putting something in virtualenv to make relocating
>> the environment easier.  There's only a few things that need to be
>> modified, I think.  That might mitigate some of these issues.
> 
> Hmm, like being able to just zip the whole virtual environment and unzip
> elsewhere and it just works? That would be awesome indeed, and make
> eggfreezer unnecessary except perhaps the little code to create an inline
> tarball.

Well, I don't know if it would just work.  There are some paths that 
need to be fixed.  I was thinking about a specific command you'd run, 
say "python -m virtualenvmove", and it'd rewrite a few things.

But I suppose I could put a check in site.py, and do the move anytime 
site.py moves.

>>>>  and generating an "install" .py file that determines the
>>>> platform and downloads the appropriate platform bundle.
>>>>
>>> Hmm, this "download" is precisely what I'm trying to avoid. My main use
>>> case is: A machine has gone down and I want to quickly put back
>>> everything together in another machine with a backup and something that
>>> contains *all* needed software. Sort of like an apt reposisory inside a
>>> dvd which lets you install debian on a machine with absolutely not net
>>> access. The "no-net" condition is just there to guarantee that all deps
>>> will be available no matter how old and discontinued they are (which if
>>> I think about it is rather ambitious... well, at least make it more
>>> likely than with the current situation)
>> With PoachEggs I've now got it working so you can build a working
>> environment, create a "requirements" file that lists everything in that
>> working environment, download all the eggs for that into a directory,
>> and then later install from that directory and disallow network access.
>>   Well, more-or-less.  It's not a single-file install like eggfreezer,
>> but they are working toward similar goals.
> 
> Yes, almost the same goals although I'd like to keep eggfreezer simple by
> leaving all the hard work of finding the right distributions to
> easy_install as much as possible.

PoachEggs is mostly focused on finding the right distributions.

>> The root (well, *one* root) of the problem is setuptools/distutils not
>> getting the platform really right, but there's also all kinds of messy
>> backward compatibility issues there, and no backward compatibility
>> issues for eggfreezer.  I'm not sure there aren't other issues.  I'm
>> also not sure that there isn't a finite number of resolvable issues.  So
>> maybe MacPorts and fink and system python on Macs are different.  But
>> that's just 3 platforms instead of 1, it's not an infinite number.  And
>> UCS2 Python is different from UCS4 on Linux, but that's really the one
>> issue I know of where Linux Pythons differ.  In theory other differences
>> could occur, but in practice there's maybe 10 platforms instead of 3,
>> and that's not unreasonable.
> 
> I've already got an idea on how to handle these special flavors inside
> eggfreezer, the only thing I'm missing are the heuristics to detect the
> platform's flavor which I cannot really investigate ATM, nor in the near
> future, due to lack of testing machines and experience on them (I've never
> had the need to compile anything on windows and never done, for example).
> 
> So, if someone can point me to, or provide, something I can use to
> reliably detect a platform and its peculiar flavor I could implement this
> in short time, I guess.

I'm not sure, but maybe u'a'.encode('unicode_internal') shows UCS2/4?  A 
quick test appears to saw yes -- the result is 'a\x00\x00\x00' on a UCS4 
build, 'a\x00' on a UCS2 build.

>> Reading a comment on the philikon article
>> (http://philikon.wordpress.com/2008/06/26/is-there-a-point-to-distributing-egg-files/#comment-47),
>> I also notice that Enthought has done some work on this, it seems by
>> fixing up the binary packages at install time.  This seems to be related
>> to an entirely different issue of the location of libraries and binary
>> incompatibilities, which I only slightly understand.
> 
> Very interesting... some code doing this is not available anywhere for me
> to study/steal, right? :)

Probably, but you'd have to ask the Enthought guys.


-- 
Ian Bicking : ianb at colorstudy.com : http://blog.ianbicking.org