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Hi Russell,

You actually propose to extend the whole nova stack to support
environment variables. Would any other driver benefit from this API
extension?

Is that what you imagine?
nova --env SQL_URL=postgres://user:password --image ....

Regarding the discussion you mentioned. Are there any public resources
to read. I kind of missed it. Most likely it was before I was part of
this community :)

thanks,
Daniel

On Mon, Dec 16, 2013 at 4:07 PM, Russell Bryant <rbryant at redhat.com> wrote:
> On 12/16/2013 09:27 AM, Daniel Kuffner wrote:
>> Hi All,
>>
>> I have submitted a new blueprint which addresses the a common pattern
>> in the docker world. A usual pattern in the docker world is to use
>> environment variables to configure a container.
>>
>> docker run -e "SQL_URL=postgres://user:password@/db" my-app
>>
>> The nova docker driver doesn't support to set any environment
>> variables. To work around this issue I used cloud-init which works
>> fine. But this approach has of course the drawback that a) I have to
>> install the cloud init service. and b) my docker container doesn't
>> work outside of openstack.
>>
>> I propose to allow a user to set docker environment variables via nova
>> instance metadata. The metadata key should have a prefix like ENV_
>> which can be used to determine all environment variables. The prefix
>> should be removed and the remainder key and vaule will be injected.
>>
>> The metadata can unfortunately not be set in horizon but can be used
>> from the nova command line tool and from heat. Example heat:
>>
>> myapp:
>>     Type: OS::Nova::Server
>>     Properties:
>>       flavor: m1.small
>>       image: my-app:latest
>>       meta-data:
>>         - ENV_SQL_URL: postgres://user:password@/db
>>         - ENV_SOMETHING_ELSE: Value
>>
>>
>> Let me know what you think about that.
>>
>> Blueprint: https://blueprints.launchpad.net/nova/+spec/docker-env-via-meta-data
>
> Thanks for starting the discussion.  More people should do this for
> their blueprints.  :-)
>
> One of the things we should be striving for is to provide as consistent
> of an experience as we can across drivers.  Right now, we have the
> metadata service and config drive, and neither of those are driver
> specific.  In the case of config drive, whether it's used or not is
> exposed through the API.  As you point out, the meta-data service does
> technically work with the docker driver.
>
> I don't think we should support environment variables like this
> automatically.  Instead, I think it would be more appropriate to add an
> API extension for specifying env vars.  That way the behavior is more
> explicit and communicated through the API.  The env vars would be passed
> through all of the appropriate plumbing and down to drivers that are
> able to support it.
>
> This is all also assuming that containers support is staying in Nova and
> not a new service.  That discussion seems to have stalled.  Is anyone
> still pushing on that?  Any updates?
>
> --
> Russell Bryant
>
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