snapcraft conda plug-in?

[Bill Janssen]

Zygmunt Krynicki <zygmunt.krynicki at canonical.com> wrote:

> On Wed, Jun 15, 2016 at 9:49 PM, Bill Janssen <janssen at parc.com> wrote:
> 
> > I've got a big package, multiple programs, that I assemble in one
> > directory under /opt/goodstuff, using conda as the packaging system --
> > the goodstuff directory tree is a conda 'env'.  It seems that this
> > should be easy to re-package as a snap.  However, conda does a few
> > things that have to be changed, or undone, for snap:
> >
> >   1) It mungs shebangs; that is, a header like "#!/usr/bin/env python"
> >   gets changed to "#!/opt/goodstuff/bin/python".  I think that would
> >   have to be undone; what snapcraft stage should that occur in?
> >
> 
> Hey
> 
> Remember that your snap will most likely ship python by itself.

Right.  It's already present under /opt/goodstuff/bin/, so it will
get copied into the snap.

> The shebang line doesn't matter because the root filesystem at the
> time your snap will execute is not going to show much of the host
> distribution file system.

So how is a shebang in a snap script resolved?  Or are shebangs not
resolved?  That means I'd have to gen up a whole new line of launchers
for my executables.

> >   2) It symlinks in some of the binaries; for example,
> >   /opt/goodstuff/bin/conda is a symlink to /opt/conda/bin/conda.  Those
> >   would have to be reified (copied), perhaps in the "pull" stage?
> >
> 
> In general, you should install your snap to "anything you want" and that

I'm confused; I'm talking about building the snap squashfs, not
installing it.  I originally thought I could just use the "copy"
plug-in, but that doesn't seem to work.  When I figure up my Python
script (now a command under /snap/bin), I get this error:

$ /snap/bin/goodstuff
ImportError: No module named site
$

The shebang line (in /snap/goodstuff/x1/bin/goodstuff) is not modified;
it still says, "#!/opt/goodstuff/bin/python".  So I think this has to
be changed.

> will show up under /snap/conda/current/. In this case you would have
> /snap/conda/current/opt/conda/bin/conda. You should try to simplify the
> structure though it matters little in practice.

Do you mean that I should just copy the entire conda install?  Yes, that
would work, I think.  However, it would probably also copy lots of other
stuff that I don't want.

The thing is, conda already provides a way to assemble lots of parts into
an integrated environment.  I'd like to re-use that capability; I've already
written the conda yaml for goodstuff.

> >   3) It rewrites RPATH on some platforms (OS X), but perhaps not on
> >   Linux, I'll have to check.  That should be redone to accord with snap.
> >
> 
> This should be harmless but note that currently snapcraft has a bug when
> executables use rpath.

What bug is that?

> It is better to strip rpath and rely on LD_LIBRARY_PATH that snapcraft
> and snapd automatically arrange for you.

Yes, but...  I tend to use systems like JModelica which has its own
ideas about who should set LD_LIBRARY_PATH and what it should be set to.

> >   4) It's not a completely clean package.  There are some dependencies,
> >   like "python-dbus", that are hard to build, and therefore installed
> >   via apt-get.
> >
> 
> That's okay.

Right.

> 
> 
> 
> >
> > Seems to me that the way to this is with a conda plug-in for snapcraft
> > that would take a conda env and package it; "copy" with fixes for conda.
> >
> > Any suggestions about this?  What would be a good plug-in to use as a
> > template?
> 
> 
> You can put a custom plugin alongside your snapcraft.yaml file. You can
> experiment with the make plugin since makefiles are familiar to many people
> and you can use that as a way to just put files in various places and see
> what happens.
> 
> Oh and while you experiment, do use "snap try", it will be much faster than
> rebuilding the snap all the time.

Thanks for the tip!

Bill

> 
> Best regards
> ZK
> 
> 
> 
> >
> > Bill
> >
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