[openstack-dev] [Neutron][IPAM] Arbitrary JSON blobs in ipam db tables

Jay Pipes jaypipes at gmail.com
Thu Nov 5 16:55:50 UTC 2015


On 11/04/2015 04:21 PM, Shraddha Pandhe wrote:
> Hi Salvatore,
>
> Thanks for the feedback. I agree with you that arbitrary JSON blobs will
> make IPAM much more powerful. Some other projects already do things like
> this.

:( Actually, though "powerful" it also leads to implementation details 
leaking directly out of the public REST API. I'm very negative on this 
and would prefer an actual codified REST API that can be relied on 
regardless of backend driver or implementation.

> e.g. In Ironic, node has driver_info, which is JSON. it also has an
> 'extras' arbitrary JSON field. This allows us to put any information in
> there that we think is important for us.

Yeah, and this is a bad thing, IMHO. Public REST APIs should be 
structured, not a Wild West free-for-all. The biggest problem with using 
free-form JSON blobs in RESTful APIs like this is that you throw away 
the ability to evolve the API in a structured, versioned way. Instead of 
evolving the API using microversions, instead every vendor just jams 
whatever they feel like into the JSON blob over time. There's no way for 
clients to know what the server will return at any given time.

Achieving consensus on a REST API that meets the needs of a variety of 
backend implementations is *hard work*, yes, but it's what we need to do 
if we are to have APIs that are viewed in the industry as stable, 
discoverable, and reliably useful.

Best,
-jay

Best,
-jay

> Hoping to get some positive feedback from API and DB lieutenants too.
>
>
> On Wed, Nov 4, 2015 at 1:06 PM, Salvatore Orlando
> <salv.orlando at gmail.com <mailto:salv.orlando at gmail.com>> wrote:
>
>     Arbitrary blobs are a powerful tools to circumvent limitations of an
>     API, as well as other constraints which might be imposed for
>     versioning or portability purposes.
>     The parameters that should end up in such blob are typically
>     specific for the target IPAM driver (to an extent they might even
>     identify a specific driver to use), and therefore an API consumer
>     who knows what backend is performing IPAM can surely leverage it.
>
>     Therefore this would make a lot of sense, assuming API portability
>     and not leaking backend details are not a concern.
>     The Neutron team API & DB lieutenants will be able to provide more
>     input on this regard.
>
>     In this case other approaches such as a vendor specific extension
>     are not a solution - assuming your granularity level is the
>     allocation pool; indeed allocation pools are not first-class neutron
>     resources, and it is not therefore possible to have APIs which
>     associate vendor specific properties to allocation pools.
>
>     Salvatore
>
>     On 4 November 2015 at 21:46, Shraddha Pandhe
>     <spandhe.openstack at gmail.com <mailto:spandhe.openstack at gmail.com>>
>     wrote:
>
>         Hi folks,
>
>         I have a small question/suggestion about IPAM.
>
>         With IPAM, we are allowing users to have their own IPAM drivers
>         so that they can manage IP allocation. The problem is, the new
>         ipam tables in the database have the same columns as the old
>         tables. So, as a user, if I want to have my own logic for ip
>         allocation, I can't actually get any help from the database.
>         Whereas, if we had an arbitrary json blob in the ipam tables, I
>         could put any useful information/tags there, that can help me
>         for allocation.
>
>         Does this make sense?
>
>         e.g. If I want to create multiple allocation pools in a subnet
>         and use them for different purposes, I would need some sort of
>         tag for each allocation pool for identification. Right now,
>         there is no scope for doing something like that.
>
>         Any thoughts? If there are any other way to solve the problem,
>         please let me know
>
>
>
>
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