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I am sending this now to gauge interest and get feedback on what I see as an impending necessity — updating the existing "haproxy" driver, replacing it, or both. Though we're not there yet, it is probably best to at least start the discussion now, to hopefully limit some fragmentation that may be starting around this concept already.

To begin with, I should probably define some terms. Following is a list of the major things I'll be referencing and what I mean by them, since I would like to avoid ambiguity as much as possible.

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---- Glossary
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HAProxy: This references two things currently, and I feel this is a source of some misunderstanding. When I refer to  HAProxy (capitalized), I will be referring to the official software package (found here: http://haproxy.1wt.eu/ ), and when I refer to "haproxy" (lowercase, and in quotes) I will be referring to the neutron-lbaas driver (found here: https://github.com/openstack/neutron/tree/master/neutron/services/loadbalancer/drivers/haproxy ). The fact that the neutron-lbaas driver is named directly after the software package seems very unfortunate, and while it is not directly in the scope of what I'd like to discuss here, I would love to see it changed to more accurately reflect what it is --  one specific driver implementation that coincidentally uses HAProxy as a backend. More on this later.

Operator Requirements: The requirements that can be found on the wiki page here:  https://wiki.openstack.org/wiki/Neutron/LBaaS/requirements#Operator_Requirements and focusing on (but not limited to) the following list:
* Scalability
* DDoS Mitigation
* Diagnostics
* Logging and Alerting
* Recoverability
* High Availability (this is in the User Requirements section, but will be largely up to the operator to handle, so I would include it when discussing Operator Requirements)

Management API: A restricted API containing resources that Cloud Operators could access, including most of the list of Operator Requirements (above).

Load Balancer (LB): I use this term very generically — essentially a logical entity that represents one "use case". As used in the sentence: "I have a Load Balancer in front of my website." or "The Load Balancer I set up to offload SSL Decryption is lowering my CPU load nicely."

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---- Overview
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What we've all been discussing for the past month or two (the API, Object Model, etc) is being directly driven by the User and Operator Requirements that have somewhat recently been enumerated (many thanks to everyone who has contributed to that discussion!). With that in mind, it is hopefully apparent that the current API proposals don't directly address many (or really, any) of the Operator requirements! Where in either of our API proposals are logging, high availability, scalability, DDoS mitigation, etc? I believe the answer is that none of these things can possibly be handled by the API, but are really implementation details at the driver level. Radware, NetScaler, Stingray, F5 and HAProxy of any flavour would all have very different ways of handling these things (these are just some of the possible backends I can think of). At the end of the day, what we really have are the requirements for a driver, which may or may not use HAProxy, that we hope will satisfy all of our concerns. That said, we may also want to have some form of "Management API" to expose these features in a common way.

In this case, we really need to discuss two things:

  1.  Whether to update the existing "haproxy" driver to accommodate these Operator Requirements, or whether to start from scratch with a new driver (possibly both).
  2.  How to expose these Operator features at the (Management?) API level.

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---- 1) Driver
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I believe the current "haproxy" driver serves a very specific purpose, and while it will need some incremental updates, it would be in the best interest of the community to also create and maintain a new driver (which it sounds like several groups have already begun work on — ack!) that could support a different approach. For instance, the current "haproxy" driver is implemented by initializing HAProxy processes on a set of shared hosts, whereas there has been some momentum behind creating individual Virtual Machines (via Nova) for each Load Balancer created, similar to Libra's approach. Alternatively, we could use LXC or a similar technology to more effectively isolate LBs and assuage concerns about tenant cross-talk (real or imaginary, this has been an issue for some customers). Either way, we'd probably need a brand new driver, to avoid breaking backwards compatibility with the existing driver (which does work perfectly fine in many cases). In fact, it's possible that when we begin discussing this as a broader community, we might decide to create more than one additional driver (depending on which approaches people want to use and what features are most important to them). The only concern I have about that outcome is the necessary amount of code-reuse, and whether it would be possible to share certain aspects of these drivers without too much copy/pasting.

An example of one possible new driver could be the following (just off the top of my head):
* Use a pair of new Nova VMs for each LB (Scalability), configured to use a Shared IP (High Availability).
* Log to Swift / Ceilometer (Logging / Alerting / Metering).
* Provide calls that could be exposed via a Management API to show low level diagnostic details (Diagnostics).
* Provide calls that could be exposed via a Management API to allow syncing/reloading existing LBs or moving them across clusters (Recoverability, DDoS Mitigation).
This new driver would be named to reflect what features it provides, or at least given a unique name that can be referenced without confusion (something like "OpenHA" or "NovaHA" would work if that's not taken).

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---- 2) Management API
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Going forward, it should then be required (can we enforce this?) that any mainline driver include support for calls to handle these named Operator Requirements, for example: obtaining logs (or log locations?), diagnostic information, and admin type actions including rebuilding or migrating LB instances. So far we haven't really talked about any of these features in depth, though I believe the general need for a Management API was alluded to on several occasions. Should we shelve this discussion until after we have the User API specification locked down? Should we begin defining a contract for this Management API at the summit, since it would be the main gateway to the Operator Requirements that we have all been stressing recently?

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---- Summary
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I would apologize for not having much concrete specification here, but I think it is better to validate my basic assumptions first, before jumping deeper down this rabbit hole. The type of comments I'm hoping to prompt are along the lines of:
* "We should just focus on the existing haproxy driver."
* "We should definitely collaborate to make a new driver as a community."
* "I don't think a Management API is necessary."
* "This is definitely what I was thinking we'd need to do."
 Anything specific implementation details I've mentioned are intended be taken as one possible example, not as a well thought out proposal. I am, as one might say, "speaking my mind". My hope is that some of this will simmer on the general subconscious. I'd like to hear what the general consensus is on these topics, because these are some of the assumptions I've been operating under during the rest of our discussions, and if they're invalid, I may need to rebase my view on the API discussion as a whole.

Thanks ya'll, I'm looking forward to getting some additional viewpoints!
--Adam Harwell (rm_work)
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