[openstack-dev] [nova][nova-docker] docker environment variables and error handling

Federico Michele Facca federico.facca at create-net.org
Fri Jul 10 14:39:49 UTC 2015

trying to add a little of context to the request of daniel :)

we are playing with nova-docker, and we realized that

1) it's unclear (or not supported) passing enviroment variable through
userdata. probably the current version of  IBM Cloud Manager with OpenStack
V4.3 indeed does implement a mechanism [1], but is not commited on

2) a large number of containers will fail during the start because of
missing required enviroment parameters. the user in the interface will be
notified a "No valid host found", which is quite puzzling and not very user
friendly :)

so we are tyring to find out:

about 1) is there already an official solution? not much work also to
implement the same solution proposed in [1]. most important is agreeing on
how to pass such parameters (also without a metadata server and cloud-init,
e.g. using user_data).

about 2) unfortunately the docker remote client regardless any error during
the start of a containers returns you a simple 204 code. what can be done,
is checking - after the "start" command - if the container as an error code
using the container inspector. still this has 2 inconvinients: a) if the
inspections occurs before the container exiting with error, you will not be
able to detect the issue; b) we tried to retrieve the "error message" but
apparently is not available through the docker apis, while on command line
using "docker run..." you would get a nice message such as: please set this
any nice idea on how to solve this?



On Fri, Jul 10, 2015 at 11:03 AM, Daniel Depaoli <
daniel.depaoli at create-net.org> wrote:

> Hi all.
> I have a brief question about nova and nova-docker.
> In nova-docker I add a piece of code when I raise an exception, in
> particular in 'novadocker/virt/docker/driver.py', function
> '_start_container':
> *
> exitcode=self.docker.inspect_container(container_id)['State']['ExitCode']*
> *        if exitcode > 0:*
> *            raise exception.NoValidHost(reason="Error in docker exit
> code")*
> In nova cli or horizon I expect to see my error and not the general error
> raised after my code.
> Can you help me?
> Daniel
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