Add ability to set settings from environment variables

[Guilhem Lettron]

To ease deployment and configuration, we want to being able to use environment variables as settings from horizon django app.

A use case can be, for example, to set `SECRET_KEY` in a uwsgi configuration file provisioned by chef/puppet...

With env variables, cfg software doesn't have to know very much about horizon (and its update) and can add specific settings.

Another use case is for packaging to set STATIC_ROOT (and push files in there own package) without having to change a file.

[Timur Sufiev (tsufiev-x)]

The solution is the same as in bug 1399580: just pull values out of environment variables in your local_settings - then it will be imported into settings.py.

[Guilhem Lettron (guilhem-fr)]

Are you just reading what people put in description???

I put many use case when `local_settings` is invalid and can't be used.

As a devops, I pushed this solution on many proprietary Django software with huge success.

Maybe my solution with `exec(` is bad and I have to work on it, but this feature is really useful and doesn't concern local_settings.

You may want me to explain more why local_settings is invalid, but please don't close ticket so quickly!

[Timur Sufiev (tsufiev-x)]

Guilhem, both cases you mentioned (overriding SECRET_KEY and STATIC_ROOT) could be easily overridden in openstack_dashboard.local.local_settings which is usually symlinked from /etc/openstack-dashboard/local_settings. Please refer to the docs at http://docs.openstack.org/developer/horizon/topics/customizing.html - Horizon Dashboard is quite customizable out of the box.

[Guilhem Lettron (guilhem-fr)]

I'm aware of this use case. And in fact we was using it before.

But there is MANY bad sides:
* You have to maintain this symlink... what can be really difficult (you are linking a configuration to a software change)
* local_settings is python, not a configuration file, so it's harder to create it from a (ruby) cfgmgmt software.
* if you want to separate static file at packaging moment (to do a "horizon" and a "horizon-static" package), changing local_setting with bash is hard.

I can give you code example in bash, debian packaging, chef, uwsgi conf to convince you why this is useful. :)

Moreover, my patch doesn't change anything for someone who are using local_settings.
Adding configuration from env with a prefix is really a common modern pattern.

[Timur Sufiev (tsufiev-x)]

Well, you might be interested with this one: https://review.openstack.org/#/c/100521/

[Guilhem Lettron (guilhem-fr)]

it's related of course.... but it doesn't help on packaging side.

And my patch is only ~5 lines... not changing all configuration stuff.
It's like using a hammer to kill a fly

[Radomir Dopieralski (deshipu)]

If you set a custom DJANGO_SETTINGS_MODULE, you can have your own module that then imports from any number of other files, managed by puppet or generated otherwise.

[OpenStack Infra (hudson-openstack)]

Change abandoned by David Lyle (<email address hidden>) on branch: master
Review: https://review.openstack.org/139112
Reason: This review is > 4 weeks without comment and currently blocked by a core reviewer with a -2. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and contacting the reviewer with the -2 on this review to ensure you address their concerns.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/201270

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/201270
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=f341decaebacbb29ed2fc75dc72ee673dca2133a
Submitter: Jenkins
Branch: master

commit f341decaebacbb29ed2fc75dc72ee673dca2133a
Author: David Lyle <email address hidden>
Date: Mon Jul 13 11:40:32 2015 -0600

    Allow STATIC_ROOT override

    STATIC_ROOT is a file system location. It does not need to be tied
    to WEBROOT.

    Change-Id: I4935c5d8bd883cb5f091af22582e942f13aa5100
    Partial-Bug: #1399585

[Andrew Balfour (andrew-balfour)]

Added the kilo-backport-potential tag as overriding STATIC_URL in local_settings worked fine in Juno, but was broken in Kilo by the "Fixing changing WEBROOT from / " changeset [1]

The fix for this bug would make it work again in Kilo as well.

[1] - https://github.com/openstack/horizon/commit/18dddd97da19af894a0974e3560197036ea8969a

[Gary W. Smith (gary-w-smith)]

Un-assigning as there has been no progress on this in a couple years.

[Akihiro Motoki (amotoki)]

This can be done by using your own (local_)settings file.
Other OpenStack projects do not support configuration via environment variables.

In addition, we are exploring to support configuration through oslo-config style.
I believe the motivation of this bug report can be addressed by this effort.