[openstack-dev] [DevStack] Python dependencies: PyPI vs distro packages

Joshua Harlow harlowja at yahoo-inc.com
Mon Aug 5 18:59:12 UTC 2013

Just so people know how anvil (the other tool) is doing it, and which
might be useful.

Anvil goes through a few stages to get a working openstack system up and

1. Downloaded all the git repos for the desired components
2. Extract all the python requirements from said repos
3. Collapse all the python requirements into 1 set (report if this isn't
  a. Also: https://github.com/stackforge/anvil/tree/master/tools#multipip
4. Search yum for packages which will satisfy said python requirements
5. Download all non satisfable python requirements
6. Build rpm packages from non satisfable python requirements
7. Build rpm packages from git repos (PBR made this a lot easier)
  a. Also: https://github.com/stackforge/anvil/tree/master/tools#py2rpm
8. Create 2 yum repos (dependencies get a repo, openstack projects get a
9. Install from repos.
10. Configure component config files.
11. Start.
12. Profit.

This has worked out quite well and gets around the problem of trying to
use 2 packaging systems and the conflicts there-in.

The setuptools example is a good one, in the anvil way of working it just
creates a 0.9.8 rpm and upgrades the existing one, no removal needed. Yum
will break if this isn't possible to install.
https://github.com/stackforge/anvil/tree/master/tools#yyoom was a tool
built to help in this process.

PS. There isn't much specifc about anvil and rpms, it can likely built apt
packages if wanted, just needs to be similar logic.

On 8/5/13 10:03 AM, "Dean Troyer" <dtroyer at gmail.com> wrote:

>[Moving a discussion from https://review.openstack.org/40019 to the ML
>to get a wider audience]
>We've been around this block more than once so let's get it all
>documented in one place and see where to go next.  Skip down to
>############# for more actual discussion...
>* OpenStack now has an official list of Python package versions
>required in https://review.openstack.org/p/openstack/requirements
>* This list is rarely completely available in any packaged Linux distro
>* Developers like new packages that fix their immediate problem
>* Packagers dislike the treadmill of constantly upgrading packages for
>many reasons (stability, effort, etc)
>* Running OpenStack on certain long-term-stability distros (RHEL6) is
>seriously a challenge due to the number of out-of-date components,
>specifically here many of the python-* packages.
>* Fedora and RHEL6 have a nasty configuration of telling pip to
>install packages into the same location as RPM-installed packages
>setting up hard-to-diagnose problems and irritating sysadmins
>everywhere.  FTR, Debian/Ubuntu configure pip to install into
>/usr/local and put '/usr/local/lib/python2.7/dist-packages' ahead of
>'/usr/lib/python2.7/dist-packages' in sys.path.
>* Replacing setuptools on RHEL6 illustrated another issue: removing
>python-setuptools took with it a number of other packages that
>depended on it.
>* OpenStack devs are not in the packaging business.  This has been
>decided [citation required?].  Fortunately those in the packaging
>business do contribute to OpenStack (THANKS!) and do make a huge
>effort to keep up with things like the Ububntu cloud Archive and Red
>Hat's RDO.
>The last week or so of attempting to install Python prereqs from
>requirements.txt and installing pip 1.4 to support that rather than
>re-invent the wheel and all of the fallout from that illustrates
>clearly that neither approach is going to solve our problem.
>Summary of the discussion in the review (paraphrased, read the review
>to see where I got it wrong):
>* packages are evil: we develop and gate based on what is available in
>requirements.txt and a non-zero number of those are only in PyPI
>* Anvil solved this already: resolves requirements into the RPM
>package list and packages anything required from PyPI
>* ongoing worries about pip and apt/rpm overwriting each other as
>additional things are installed
>* packages are necessary:
>My specific responses:
>* proposals to use a tool to automatically decide between package and
>PyPI (harlowja, sdague):  this works well on the surface, but anything
>that does not take in to account the dependencies in these packages
>going BOTH ways is going to fail.  For example: on RHEL6 setuptools is
>0.6.10, we want 0.9.8 (the merged release w/distribute).  Removing
>python-setuptools will also remove python-nose, numpy and other
>packages depending on what is installed.  So fine, those can be
>re-installed with pip.  But a) we don't want to rebuild numpy (just
>bear with me here), and b) the packaged python-nose 0.10.4 meets the
>version requirement in requirements.txt so the package will be
>re-installed, bringing with it python-setuptools 0.6.10 overwriting
>the pip installation of 0.9.8.
>* separate proposal to build meta-packages (iwienand,
>https://review.openstack.org/39862): this would be an effective
>work-around for the problems on Fedora and RHEL6 and protect against
>the re-install problem, but this is solving a distro packaging problem
>in an upstream testing tool.  We would also need to manage these
>individually and not in a single large package, or at least split
>python-crypto and python-lxml out of the proposed package as they may
>not be installed in all configurations.
>* about-face on all-packages to all-PyPI (mtaylor): I'm still on the
>use packages where possible side but DevStack specifically is not in
>the packaging business.  If it were we'd do what Java folk (*sorry*)
>have long taken the approach for non-trivial apps to just include the
>whole damn runtime.  Write once duplicate everywhere.
>I want to propose moving forward with the following guidelines:
>* Keep a list of specific distro packages that we want to use in favor
>of PyPI for specific reasons like not recompiling native modules, i.e.
>python-crypto except on RHEL, etc
>* Continue to factor the prereq setup out of stack.sh such that
>requirements.txt is satisfied one way or another before it begins to
>install OpenStack.  tools/install_prereqs.sh and tools/install_pip.sh
>are the prototypes for this. Each distro gets a chance to get it right
>here whether by package or by PyPI.
>tl;dr: no easy solution
>Dean Troyer
>dtroyer at gmail.com
>OpenStack-dev mailing list
>OpenStack-dev at lists.openstack.org

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