[openstack-dev] [oslo][mistral] Mistral expressions package
doug at doughellmann.com
Tue Oct 10 15:10:35 UTC 2017
Excerpts from HADDLETON, Robert W (Bob)'s message of 2017-10-09 19:41:58 -0500:
> On 10/9/2017 2:35 PM, Doug Hellmann wrote:
> > Excerpts from Bob Haddleton's message of 2017-10-09 11:35:16 -0500:
> >> Hello Oslo team:
> >> The Mistral project has an expressions package  that is used to
> >> evaluate inline expressions using a context. It has a pluggable
> >> architecture that presently supports Jinja and YAQL expression
> >> evaluation. It also allows custom functions to provide Python
> >> implementations of functionality that is then made available to the
> >> expression evaluation engines.
> >> This functionality was originally developed to support dynamic
> >> processing within Mistral workflows, but is also very useful in other
> >> applications that use templates which require runtime evaluation of
> >> expressions.
> >> I'd like to explore extracting this functionality from mistral to make
> >> it more widely available with minimal dependencies.
> >> The expressions dependencies are pretty limited:
> >> Jinja2
> >> oslo.utils
> >> oslo.log
> >> stevedore
> >> yaql
> >> and since 60% are already oslo-maintained packages, it seemed like a
> >> logical place to start.
> >> I'd appreciate feedback on the topic. There is no real OpenStack
> >> dependency in the functionality, so maybe a standalone package on pypi
> >> makes sense.
> >> Thanks for your help,
> >> Bob Haddleton
> >>  https://github.com/openstack/mistral/tree/master/mistral/expressions
> >> 
> >> https://github.com/openstack/mistral/blob/master/mistral/utils/expression_utils.py#L63
> > Oslo is a good place for things like this that have no other obvious
> > home, but if the Mistral team is already managing the code is there any
> > reason they couldn't also manage the library after you pull it out of
> > the service? It's much easier for any project team to manage a library
> > now, and we have several other examples of that pattern already.
> > Doug
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> Hi Doug:
> That's probably fine, we're just not sure what the process should be and
> where the library would land? Do you have an example that we could use
> as a pattern?
The first step is to create the repository with the library code. Then
you would add that repository to the list managed by the mistral team by
modifying the project list file in the governance repository.
Any of the project client libraries would work as an example of how to
set up the CI, governance, and release configuration. I think most of
the steps are covered in
https://docs.openstack.org/infra/manual/creators.html as well.
If the code is already isolated well within the mistral repo and you
want to preserve its history, you may also want to take a look at
as a tool for making the new repository.
I'm happy to help you work out a more detailed plan. Let me know if that
would be useful.
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