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Hi Andre -

I learned a long time ago to never put myself in the middle of someone trying to come up with a project/directory/filename/variable naming convention ... but you asked. :)

I agree w/ the use of "_tx". My brain immediately thinks of the word transmit and I'd start looking around the code for the matching "_rx".

Regarding using "_db", if only database logic is in these functions then it works, but I don't know if that's always going to be true.

Going back to using the word "transaction", another valid abbreviation is "txn".
create_port_txn()
create_port()
doesn't look too bad to me.

I thought of
create_port_txn()
create_port_posttxn()
but the double "tt" didn't seem quite right to my eyes.

Oh and "_db()" looks fine too. At this point please refer to my initial sentence. :)

Thanks,
Rich


From: Andre Pech [mailto:apech at aristanetworks.com]
Sent: Wednesday, June 12, 2013 2:16 PM
To: openstack-dev
Cc: Sukhdev Kapur
Subject: Re: [openstack-dev] [networking][ml2] ML2 Mechanism Driver API proposal

Hi all,

Wanted to send an updated proposal based on the discussions at this morning's ml2 meeting. Thanks everyone for the feedback.

Main difference is the definitions of call that happen both within the transaction context and afterwards. Kyle had proposed the naming of appending _tx to the methods that happen within the transaction. After thinking about it a bit more, I ended up going with _db instead (probably the networking guy in me substituting tx with transmit :)). This is under the assumption that calls made within the transaction context are really to allocate resources within the database (there's not much else they can do given that these calls aren't supposed to block), while the non _db calls can then push whatever information is necessary to the outside controller / hardware devices, etc. Appreciate feedback on the naming.

Please see attached for the updated proposal. Feedback appreciated. I'll be working on getting these calls hooked into the ml2 plugin and will work to send out a review this weekend.

Andre

On Wed, Jun 12, 2013 at 12:25 AM, Andre Pech <apech at aristanetworks.com<mailto:apech at aristanetworks.com>> wrote:
Hi all,

As promised at the ml2 kickoff meeting last week, attached is our basic proposal for the ml2 mechanism driver API. Sorry for the delay in getting this out. We'll be on the meeting tomorrow morning and can also discuss some of these points then. Assuming we agree on the direction, we'll implement the backend calls from ml2 plugin and get this posted for review.

Our original proposal along these lines within the OVS Plugin (as described in https://blueprints.launchpad.net/quantum/+spec/ovsplugin-hardware-devices) defined a pretty specific set of methods based on our needs at the physical infrastructure layer (plug_host, unplug_host) that were called based on the parameters passed into the various quantum plugin methods (for example, if create_port is called as part of booting the VM, then call plug_host, otherwise don't).

After getting more familiar with the ml2 plugin code and looking at some of the other blueprints that are looking to make use of the MechanismDriver, we've instead gone with a more simple passthrough model using the existing plugin language of create_network / update_network / delete_network / create_port / update_port / delete_port. This makes ml2 a bit more of a "meta-plugin" on top of the various mechanism drivers, but ultimately the information passed to the mechanism driver really needs to be the same as what is passed to the associated ml2 plugin call, just filled in with more information by ml2 and the type drivers along the way. The main reason I don't love using the same names is that it doesn't really help enforce the distinction between plugins, type drivers, and mechanism drivers... but we also failed at coming up with a distinct yet equally generic set of names :). We wanted to ensure that we could handle other people's use cases and not just our own, so passing in the full dict defining the network or port seemed like an easy way to do this compared to what we had originally proposed. If people would rather see distinct names compared to the plugin and/or more restrictive and explicit parameters, that'd be fine with us too and we appreciate suggestions.

One related change that may be of interest to others is https://review.openstack.org/#/c/29767/, which adds the hostname to the port binding calls. We're also interested in getting the VM id / name passed through as well in the port bindings. Bob, not sure how this fits in with your modular l2 port binding blueprint (https://blueprints.launchpad.net/quantum/+spec/ml2-portbinding).

One question we'd love to get feedback on - for our use case, we're only going to make use of calls made within the transaction context (ie they don't block and they cause a rollback on failure). Not having a good use case for a mechanism driver call made outside the transaction context, we haven't added any apis for this (how they're planning to be used would help me name them). Anyone have any use cases for this?

Appreciate everyone's feedback. Bob, is this down the path you were thinking?

Getting the backend code hooked up to make these calls in the ml2 plugin is pretty trivial, so once this is settled we can have that posted for review pretty quickly.

Thanks
Andre and Sukhdev

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