diskimage-builder/diskimage_builder/elements/pypi/README.rst
Ian Wienand 97c01e48ed Move elements & lib relative to diskimage_builder package
Currently we have all our elements and library files in a top-level
directory and install them into
<root>/share/diskimage-builder/[elements|lib] (where root is either /
or the root of a virtualenv).

The problem with this is that editable/development installs (pip -e)
do *not* install data_files.  Thus we have no canonical location to
look for elements -- leading to the various odd things we do such as a
whole bunch of guessing at the top of disk-image-create and having a
special test-loader in tests/test_elements.py so we can run python
unit tests on those elements that have it.

data_files is really the wrong thing to use for what are essentially
assets of the program.  data_files install works well for things like
config-files, init.d files or dropping documentation files.

By moving the elements under the diskimage_builder package, we always
know where they are relative to where we import from.  In fact,
pkg_resources has an api for this which we wrap in the new
diskimage_builder/paths.py helper [1].

We use this helper to find the correct path in the couple of places we
need to find the base-elements dir, and for the paths to import the
library shell functions.

Elements such as svc-map and pkg-map include python unit-tests, which
we do not need tests/test_elements.py to special-case load any more.
They just get found automatically by the normal subunit loader.

I have a follow-on change (I69ca3d26fede0506a6353c077c69f735c8d84d28)
to move disk-image-create to a regular python entry-point.

Unfortunately, this has to move to work with setuptools.  You'd think
a symlink under diskimage_builder/[elements|lib] would work, but it
doesn't.

[1] this API handles stuff like getting files out of .zip archive
modules, which we don't do.  Essentially for us it's returning
__file__.

Change-Id: I5e3e3c97f385b1a4ff2031a161a55b231895df5b
2016-11-01 17:27:41 -07:00

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====
pypi
====
Inject a PyPI mirror
====================
Use a custom PyPI mirror to build images. The default is to bind mount one from
~/.cache/image-create/pypi/mirror into the build environment as mirror URL
file:///tmp/pypi. The element temporarily overwrites /root/.pip.conf
and .pydistutils.cfg to use it.
When online, the official pypi.python.org pypi index is supplied as an
extra-url, so uncached dependencies will still be available. When offline, only
the mirror is used - be warned that a stale mirror will cause build failures.
To disable the pypi.python.org index without using --offline (e.g. when working
behind a corporate firewall that prohibits pypi.python.org) set
DIB\_NO\_PYPI\_PIP to any non-empty value.
To use an arbitrary mirror set DIB\_PYPI\_MIRROR\_URL=http[s]://somevalue/
Additional mirrors can be added by exporting DIB\_PYPI\_MIRROR\_URL\_1=... etc.
Only the one mirror can be used by easy-install, but since wheels need to be in
the first mirror to be used, the last listed mirror is used as the pydistutils
index. NB: The sort order for these variables is a simple string sort - if you
have more than 9 additional mirrors, some care will be needed.
You can also set the number of retries that occur on failure by setting the
DIB\_PIP\_RETRIES environment variable. If setting fallback pip mirrors you
typically want to set this to 0 to prevent the need to fail multiple times
before falling back.
A typical use of this element is thus:
export DIB\_PYPI\_MIRROR\_URL=http://site/pypi/Ubuntu-13.10
export DIB\_PYPI\_MIRROR\_URL\_1=http://site/pypi/
export DIB\_PYPI\_MIRROR\_URL\_2=file:///tmp/pypi
export DIB\_PIP\_RETRIES=0
[devpi-server](https://git.openstack.org/cgit/openstack-infra/pypi-mirro://pypi.python.org/pypi/devpi-server)
can be useful in making a partial PyPI mirror suitable for building images. For
instance:
* pip install -U devpi
* devpi-server quickstart
* devpi use http://machinename:3141
* Re-export your variables to point at the new mirror:
export DIB\_PYPI\_MIRROR\_URL=http://machinename:3141/
unset DIB\_PYPI\__MIRROR\_URL\_1
unset DIB\_PYPI\__MIRROR\_URL\_2
The next time packages are installed, they'll be cached on the local devpi
server; subsequent runs pointed at the same mirror will use the local cache if
the upstream can't be contacted.
Note that this process only has the server running temporarily; see
[Quickstart: Permanent install on
server/laptop](http://doc.devpi.net/latest/quickstart-server.html) guide from
the devpi developers for more information on a more permanent setup.