[openstack-dev] a "common" client library

Jesse Noller jesse.noller at RACKSPACE.COM
Thu Jan 16 15:25:42 UTC 2014

On Jan 16, 2014, at 9:07 AM, Joe Gordon <joe.gordon0 at gmail.com<mailto:joe.gordon0 at gmail.com>> wrote:

On Thu, Jan 16, 2014 at 9:45 AM, Jesse Noller <jesse.noller at rackspace.com<mailto:jesse.noller at rackspace.com>> wrote:

On Jan 16, 2014, at 5:53 AM, Chmouel Boudjnah <chmouel at enovance.com<mailto:chmouel at enovance.com>> wrote:

On Thu, Jan 16, 2014 at 12:38 PM, Chris Jones <cmsj at tenshu.net<mailto:cmsj at tenshu.net>> wrote:
Once a common library is in place, is there any intention to (or resistance against) collapsing the clients into a single project or even a single command (a la busybox)?

that's what openstackclient is here for https://github.com/openstack/python-openstackclient

After speaking with people working on OSC and looking at the code base in depth; I don’t think this addresses what Chris is implying: OSC wraps the individual CLIs built by each project today, instead of the inverse: a common backend that the individual CLIs can wrap - the latter is an important distinction as currently, building a single binary install of OSC for say, Windows is difficult given the dependency tree incurred by each of the wrapped CLIs, difference in dependencies, structure, etc.

Also, wrapping a series of inconsistent back end Client classes / functions / methods means that the layer that presents a consistent user interface (OSC) to the user is made more complex juggling names/renames/commands/etc.

In the inverted case of what we have today (single backend); as a developer of user interfaces (CLIs, Applications, Web apps (horizon)) you would be able to:

from openstack.common.api import Auth
from openstack.common.api import Compute
from openstack.common.util import cli_tools

my_cli = cli_tools.build(…)

def my_command(cli):
compute = Compute(Auth(cli.tentant…, connect=True))

This would mean that *even if the individual clients needed or wanted to keep their specific CLIs, they would be able to use a not “least common denominator” back end (each service can have a rich common.api.compute.py<http://common.api.compute.py/> or api.compute/client.py and extend where needed. However tools like horizon / openstackclient can choose not to leverage the “power user/operator/admin” components and present a simplified user interface.

I’m working on a wiki page + blueprint to brainstorm how we could accomplish this based off of what work is in flight today (see doug’s linked blueprint) and sussing out a layout / API strawman for discussion.

Some of the additions that came out of this email threads and others:

1. Common backend should provide / offer caching utilities
2. Auth retries need to be handled by the auth object, and each sub-project delegates to the auth object to manage that.
3. Verified Mocks / Stubs / Fakes must be provided for proper unit testing

I am happy to see this work being done, there is definitely a lot of work to be done on the clients.

This blueprint sounds like its still being fleshed out, so I am wondering what the value is of the current patches https://review.openstack.org/#/q/topic:bp/common-client-library-2,n,z

Those patches mainly sync cliutils and apiutils from oslo into the assorted clients. But if this blueprint is about the python API and not the CLI (as that would be the openstack-pythonclient), why sync in apiutils?

Also does this need to go through oslo-incubator or can this start out as a library? Making this a library earlier on will reduce the number of patches needed to get 20+ repositories to use this.

Alexei and others have at least started the first stage of a rollout - the blueprint(s) needs additional work, planning and discussion, but his work is a good first step (reduce the duplication of code) although I am worried that the libraries and APIs / namespaces will need to change if we continue these discussions which potentially means re-doing work.

If we take a step back, a rollout process might be:

1: Solidify the libraries / layout / naming conventions (blueprint)
2: Solidify the APIs exposed to consumers (blueprint)
3: Pick up on the common-client-library-2 work which is primarily a migration of common code into oslo today, into the structure defined by 1 & 2

So, I sort of agree: moving / collapsing code now might be premature. I do strongly agree it should stand on its own as a library rather than an oslo incubator however. We should start with a single, clean namespace / library rather than depending on oslo directly.


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