[openstack-dev] [quantum] [LBaaS] Health monitors REST resource
Salvatore Orlando
sorlando at nicira.com
Tue Dec 4 10:06:55 UTC 2012
Hi again!
There has been some apparent silence on this thread. I say 'apparent'
because actually Oleg pushed a patch to gerrit for dealing with
subresources, and the discussion kind of moved there, as it's a lot
more convenient to discuss code.
Anyway, since nobody else chimed in on the gerrit discussion, we are
moving it back here now.
This is a summary. If you want all the details (and the code, of
course), you'll find them here:
https://review.openstack.org/#/c/16888/
While approach #4 was discarded as it did not match the conceptual LB
model, we are looking at how get the best of the remaining approaches
Youcef summarized, namely #2 and #3. (The first approach can probably
be reduced to #3 if we all agree that the 'health_monitors' collection
is still an attribute of the 'pool' resource).
While it seems there's wide agreement on being able to operate on
health_monitors as a collection (ie: adding/removing single entries),
the bit that we are still discussing is whether health_monitors should
be treated as any other attribute or as a special attribute. To the
wider audience, I just would like to remind here we're discussion on
"references" to health monitors, or basically a list of ids, rather
than the health_monitors resources themselves, which are already being
treated as first level resources.
- Alternative 1
POST /pools
{ ...pool stuff...}
And then
POST /pools/<pool-id>/health_monitors
[{"id":"id1"}, {"id": "id2"}, {"id": "id3"}]
- Alternative 2
POST /pools
{ ...pool stuff...
"health_monitors": [{"id":"id1"}, {"id": "id2"}, {"id": "id3"}]
... other pool stuff ...
}
And similarly for PUT, and GET.
The following operations will be allowed in both cases:
POST /pools/<pool_id>/health_monitors
{"id": <id>}
and
DELETE /pools/<pool_id>/health_monitors/<id>
The above linked patch is an enhancement of the Quantum API framework
for dealing with "collection attributes". It is important to note that
we have plenty of them across the Quantum API. For instance, there is
'fixed_ips' in 'port', or 'dns_nameservers' in subnets. It is
therefore important that the way in which user interacts with this
kind of attribute is consistent across the whole API; it is even more
important to not introduce any backward incompatible change while
ensuring this consistency. This is something that we need to take into
account while making a final decision. I have a feeling that the 2nd
alternative will allow to do so, and will also avoid user from having
to do two API calls when just one might be required.
Salvatore
On 27 November 2012 02:15, Youcef Laribi <Youcef.Laribi at eu.citrix.com> wrote:
> Just to summarize agreements and discussed alternatives on this topic so
> far.
>
>
>
> On pool members, I think we all agree that the workflow should be:
>
>
>
> 1. Create an empty pool (we remove the ability to specify “members”
> during this pool creation call).
>
> 2. Create members for this pool (pool_id of member is required)
>
>
>
> On health monitors, here are the alternatives we have discussed so far:
>
>
>
> 1. Approach one : “health_monitors” subresource (this is the current
> approach documented in API spec):
>
> a. Associate health_monitors with a pool:
>
> POST /pools/{pool_id}/health_monitors
>
> b. Dissociate a health_monitor with a pool
>
> DELETE /pools/{pool_id}/health_monitors/{health_monitor_id}
>
> c. Retrieve health_monitors associated with pool
>
> GET /pools/{pool_id}/health_monitors
>
> d. Retrieve pools associated with a health_monitor : No direct API
> (client has to query all pools and work it out).
>
>
>
> 2. Approach two: A “health_monitors” attribute in pool resource that
> can be updated.
>
> a. Associate health_monitors with a pool. Can be done either:
>
> i. When
> the user creates a pool (specifies the health_monitors attribute in the
> request)
>
> POST /pools/{pool_id}
>
> ii. When
> the user updates a pool
>
> 1. User retrieves the current health_monitors associated with pool
>
> GET /pools/{pool_id}
>
> 2. User adds new health_monitors and updates this list attribute by
> calling
>
> PUT /pools/{pool_id} (this overrides/replaces current list)
>
> b. Dissociate a health_monitor with a pool:
>
> i. Can
> be done by updating the pool
>
> 1. User retrieves the current health_monitors associated with pool
>
> GET /pools/{pool_id}
>
> 2. User removes health_monitors of interest and updates this
> attribute by calling
>
> PUT /pools/{pool_id} (this overrides/replaces current list)
>
> c. Retrieve health_monitors associated with pool
>
> GET /pools/{pool_id}
>
> d. Retrieve pools associated with a health_monitor : No direct API
> (client has to query all pools and work it out).
>
>
>
> 3. Approach three: “health_monitors” subresource for
> associate/dissociate only.
>
> a. Associate health_monitors with a pool (similar to current approach)
>
> POST /pools/{pool_id}/health_monitors
>
> b. Dissociate a health_monitor with a pool (similar to current
> approach)
>
> DELETE /pools/{pool_id}/health_monitors/{health_monitor_id}
>
> c. Retrieve health_monitors associated with pool
>
> GET /pools/{pool_id} (response contains “health_monitors” list attribute)
>
> d. Retrieve pools associated with a health_monitor
>
> GET /health_monitors/{health_monitor_id} (response contains “pools” list
> attribute)
>
>
>
> 4. Approach four: A new “health_monitor_template” resource.
>
> a. Create a health_monitor template
>
> POST /health_monitor_templates (in this request we specify all the
> health_monitor attributes and we get back a template ID – similar to current
> approach of creating a health monitor resource).
>
> b. Associate health_monitors with a pool (this creates a health_monitor
> resource owned by the pool)
>
> POST /health_monitors
>
> {
>
> "health_monitor_template_id": "another-uuid",
>
> "pool_id": "yet-another-uuid"
>
> }
>
> c. Dissociate a health_monitor from its pool (this removes the
> health_monitor from its owning pool)
>
> DELETE /health_monitors/{health_monitor_id}
>
> d. Retrieve all health_monitors associated with pool
>
> GET /health_monitors?pool_id=1000 (do we support filtering on collections in
> the API)
>
> e. Retrieve pools associated with a health_monitor template
>
> GET /health_monitors?health_monitor_template_id=7281
>
>
>
>
>
> Youcef
>
>
>
>
>
>
>
>
>
>
>
>
>
> From: Salvatore Orlando [mailto:sorlando at nicira.com]
> Sent: Thursday, November 22, 2012 1:27 PM
> To: OpenStack Development Mailing List
> Subject: Re: [openstack-dev] [quantum] [LBaaS] Health monitors REST resource
>
>
>
> Hi again,
>
>
>
> For health monitors, I think we are discussing two equally viable
> approaches. Both have pro and cons. As Youcef said, introducing a 'template'
> for the health monitor adds a new resource, and an intermediate step we
> probably don't want to expose to the user; I personally see the fact that
> health monitors are usually mapped 1:1 on correspoinding back-end API as
> somewhat less relevant, as I'd like to adopt a perspective completely
> focused on the user. On the other hand, we have discussed the cons of
> handling reference to health monitors as a collection attribute within
> pools. I am taking for granted that you are discounting the idea of having a
> 'list' attribute (as fixed_ips for the port resource), even if that is not
> perfect as well it probably is the simplest from a user perspective.
>
>
>
> If we go the sub-resource-like route (current proposal), we'll need to do
> some work on the Quantum API framework for supporting it. I will be more
> than happy to this piece of work.
>
>
>
> For pool members, I'd rather have a single way of doing thing rather than
> two. I think it is more natural to specify the pool_id in the member
> resource.
>
>
>
> Thanks,
>
> Salvatore
>
>
>
>
>
> On 22 November 2012 20:37, Youcef Laribi <Youcef.Laribi at eu.citrix.com>
> wrote:
>
> Hi Oleg,
>
>
>
> My intention was to keep the same APIs we have for associating/dissociating
> a pool with a health_monitor. The new APIs will be used for retrieving
> (GET).
>
>
>
> Yes, I know it’s not ideal because a health_monitor looks like a
> sub-resource of pool in the associate/dissociate calls (doing it the other
> way around is no better either), but I don’t think it’s a big deal from a
> user perspective, and will keep the API simple instead of introducing a new
> REST entity.
>
>
>
> Thanks
>
> Youcef
>
>
>
>
>
>
>
> From: Oleg Bondarev [mailto:obondarev at mirantis.com]
> Sent: Thursday, November 22, 2012 2:05 AM
>
>
> To: 'OpenStack Development Mailing List'
> Subject: Re: [openstack-dev] [quantum] [LBaaS] Health monitors REST resource
>
>
>
> Hi Youcef,
>
> I have one question here: with what API calls do you suggest to
> associate/disassociate health monitors with a pool?
>
>
>
> Thanks,
>
> Oleg
>
>
>
> From: Youcef Laribi [mailto:Youcef.Laribi at eu.citrix.com]
> Sent: Thursday, November 22, 2012 12:12 AM
> To: OpenStack Development Mailing List
> Subject: Re: [openstack-dev] [quantum] [LBaaS] Health monitors REST resource
>
>
>
> Hi Salvatore,
>
>
>
> Thank you for your thorough analysis and helping the team reconcile a good
> API design with an easy way to implement it.
>
>
>
> I think we need to make a distinction between pool members and health
> monitors.
>
> Indeed the former exist only within a pool [1], whereas the latter can be
> defined without any pool [2].
>
> So for the pool members, I agree we probably don't want to specify them in
> API calls for 'pool' resources.
>
> In particular [3] seems strange in my opinion, as it is assuming the members
> already exist. In another thread I think there was a suggestion to make the
> member's pool_id attribute optional, but my opinion is that probably we
> should remove the members attribute for the pool resource (at least on
> create/update calls). It is fine IMHO to return a list of member ids on GET
> operations for pools.
>
>
>
> Yes today we have two ways of putting members into pools:
>
> 1. Create an empty pool, and then create members using the created
> pool_id
>
> 2. Create members (with no pool_id) and then create a pool containing
> those members
>
>
>
> We can eliminate the second workflow to simplify as you suggested, so there
> would be only one way of creating members in pools.
>
>
>
> The question after this, is how do I get the members of a pool (a very
> common operation). Here again, we have three possible ways:
>
>
>
> 1. Use filtering: GET /members?pool_id=1000
>
> 2. Have a dedicated REST API that reflects the fact the members belong
> to a pool: GET /pools/1000/members
>
> 3. Return the list of members of a pool in the pool response payload
> of: GET /pools/1000
>
>
>
> I favor the second approach but I can settle for the 3rd one, even though
> this requires more work from a user to find the “members” attribute on the
> response. What is your opinion on this?
>
>
>
> Instead the health monitors are slightly different, since they are in a n:m
> relationship with the pool resource. pool and pool members are instead on a
> 1:n relationship.
>
> The approach currently adopted in the API specification [4] makes sense from
> a REST perspective. IMHO it makes more sense than having distinct member
> action such as:
>
> PUT /pools/<pool-id>/associate_health_monitor and PUT
> /pools/<pool-id>/disassociate_health_monitor. As some contributors to this
> thread have pointed out, this can generate confusion in final users, as they
> might wonder whether an id or a full object definition is required. In that
> case I would consider the following:
>
>
>
> {POST/DELETE} /pools/<pool-id>/health_monitor_ids
>
>
>
> Sub-resources map very well onto a ORM model.
>
>
>
> Yes we are on the same page here, although I favor calling the sub-resource
> simply “health_monitors” instead of “health_monitor_ids” or
> “health_monitor_references”, purely from an aesthetic perspective, but I
> haven’t got a strong opinion on this.
>
>
>
> However, let's imagine you want to retrieve the list of pools which are
> using a health_monitor. How would you do that? In theory you could add that
> filter to the pools resource, so:
>
>
>
> GET /pools?health_monitor_id=<your_health_monitor> would return you this
> kind of list.
>
>
>
> With this approach it is important to keep in mind is that a GET /pools is
> supposed to look only into 'pool' resources. Adding this kind of capability
> would require us to do joins according to the type of filter specified (and
> we will also have to document it). No big deal, but still something to keep
> in mind.
>
>
>
> Yes this call doesn’t make sense since there is currently no attribute
> called “health_monitor_id” in a pool resource you can filter on. User can
> accomplish this themselves by retrieving all pool’s health monitor
> associations, and filtering the ones that contain the health_monitor of
> interest
>
>
>
> GET /pools/1000/health_monitors
>
> GET /pools/2000/health_monitors
>
>
>
> Etc.
>
>
>
> After all, these kind of request “which pools use monitor X” are not very
> common or necessary for the workflow of the service. There would be a lot
> many more questions like this that cannot be directly mapped to an API call,
> and need the user to do some filtering and joining on their own.
>
>
>
> An alternative is to regard the health_monitor as a 'template'. I am not
> sure if this is valid within the LB world, but I have the impression it is
> ok to assume that a health monitor does not actually exist until it is
> associated with a pool.
>
>
>
> In NetScaler, F5 and similar products, health monitors are created
> beforehand just like in the API, and then they are “bound” to pools (our
> association API), so the mapping will be more natural.
>
>
>
> In this case 'definitions' for health monitors could be managed in the
> following way:
>
>
>
> { GET/POST/PUT/DELETE } /health-monitor-templates
>
>
>
> And association/disassociation with pools can be managed in the following
> way:
>
>
>
> {GET/POST/DELETE} /health-monitors
>
>
>
> The response here would look like the following:
>
>
>
> {
>
> "health_monitor_id": "uuid",
>
> "health_monitor_template_id": "another-uuid",
>
> "pool_id": "yet-another-uuid"
>
> }
>
>
>
> I think both approaches are equivalent. The first is represents a good
> mapping on the ORM model, while the second a mapping on the ER model.
>
> The first will need work to the Quantum's framework, whereas the latter can
> be implemented using the framework as it is.
>
> I have a slight preference for the second option, but no strong opinion, as
> I believe the first approach makes sense too.
>
>
>
> I think adding a concept of health_monitor templates just complicate matters
> even more. The issue we have is not how to associate monitors and pools,
> these are simple API calls, but answering the following questions
>
>
>
> 1. What are the health_monitors associated with a pool?
>
> 2. What are the pools associated with a health monitor?
>
>
>
> I propose when retrieving a pool, we simply return the list of
> health_monitors associated with it, and for a health_monitor the list of
> pools associated with it. These are only returned for GET (they are
> read-only attributes), they are not used for creation or update (we use the
> associate/dissociate APIs already there), so this would translate in
> answering the above questions to this:
>
>
>
> 1. Health monitors associated with a pool: GET /pools/{pool_id}
> (response contains a “health_monitors” (or health_monitor_ids J) attribute)
>
> 2. Pools associated with a health_monitor: GET
> /health_monitors/{health_monitor_id} (response contains a “pools”
> attribute)
>
>
>
> This way we avoid the issue of sub-resource modeling, and keep the API
> simple (at a cost of slightly more work for the API caller). What do you
> think?
>
>
>
> Youcef
>
>
>
>
>
>
>
> On 20 November 2012 09:51, Oleg Bondarev <obondarev at mirantis.com> wrote:
>
> Hi Youcef, team,
>
>
>
> AFAIK python clients (quantum, nova, etc.) usually expose both CLI and
> python API which I believe should be used in Horizon and other projects. So
> I still think that python-quantumclient is the right place for adding
> shortcuts.
>
>
>
> A agree that improving api/v2 to support sub-resources is a good idea and
> will be useful. I also agree that “GET /v1.0/pools/{pool_id}/members” looks
> natural but only in case when member is an actual sub-resource of a pool.
> Resources and sub-resources in the Quantum extension framework are
> distinctly separated. In our case members and health monitors are top level
> resources – so adding them also as sub-resources is kind of hack, and may be
> misleading for those who reads the code – all for the sake of having
> shortcuts in REST.
>
> From my point of view it’s clear enough from our REST API that members
> belong to a pool since they have pool_id field and pool in its turn has
> members field.
>
>
>
> Hey we have a pretty long discussion here J, would be great to hear anybody
> else from the team and make a final decision.
>
> Salvatore, could you please share your thoughts?
>
>
>
> Thanks,
>
> Oleg
>
>
>
> From: Youcef Laribi [mailto:Youcef.Laribi at eu.citrix.com]
> Sent: Tuesday, November 20, 2012 1:01 AM
>
>
> To: OpenStack Development Mailing List
> Subject: Re: [openstack-dev] [quantum] [LBaaS] Health monitors REST resource
>
>
>
> Yes Oleg, some people will use the CLI to drive the LBaaS service, Horizon
> portal will use the API, and other applications will use mainly the API.
> Most people will understand the service by reading its APIs.
>
>
>
> Yes, you can list the members of pool 1000 through query string filtering
> by doing:
>
>
>
> GET /v1.0/members?pool_id=1000
>
>
>
> But as I said before, it’s more natural to use the following to get the
> pool’s members:
>
>
>
> GET /v1.0/pools/{pool_id}/members
>
>
>
> Since members really belong to a pool. As you said, if we are improving
> Quantum to support REST sub-resources then this is the preferred approach I
> would advocate.
>
>
>
> Youcef
>
>
>
> From: Oleg Bondarev [mailto:obondarev at mirantis.com]
> Sent: Monday, November 19, 2012 1:23 AM
> To: 'OpenStack Development Mailing List'
> Subject: Re: [openstack-dev] [quantum] [LBaaS] Health monitors REST resource
>
>
>
> I also surely agree that “/pools/{pool_id}/health_monitor_references“ looks
> ugly and I don’t want it to look like this.
>
> My only concern is that treating health monitor references as a sub-resource
> (and hence changes in api/v2) brings additional complexity to the code when
> it can be done simpler: using filters for listing health monitors of a pool
> and member actions for associate/disassociate (as in l3 extension). But
> probably it is ok given that handling sub-resources may be useful in future
> anyway.
>
>
>
> Another question I have is: where will these REST calls be used except
> python-quantumclient? I thought that only client api matters for end users.
> So the purpose of having kind of shortcuts for listing members and health
> monitors of a pool in REST API (instead of using filters) is not completely
> clear for me.
>
>
>
> Thanks,
>
> Oleg
>
>
>
> From: Salvatore Orlando [mailto:sorlando at nicira.com]
> Sent: Friday, November 16, 2012 9:32 PM
> To: OpenStack Development Mailing List
> Subject: Re: [openstack-dev] [quantum] [LBaaS] Health monitors REST resource
>
>
>
> Hi Youcef,
>
>
>
> Thanks for the clarification. I was pretty sure this was well thought in the
> API design, as I wrote in my previous post :)
>
>
>
> The naming for the attribute on the pool which references health_monitors is
> a discussion worth having. I have very little data points for comparison
> with other parts of Quantum and Openstack APIs. The only similar bit is
> probably the network-subnet relationship. In the response for a GET
> /networks/<network-id> a list of subnet identifiers is returned. The name
> for the list attribute is just 'subnets'. However, as this is a read-only
> attribute there is no need for handling it as a sub-resource. Response
> sample is available at [1]
>
>
>
> Between handling the collection of health monitor references as a
> sub-resource and having member actions for CRUD operations, I prefer the
> first solution. I am happy to offer any kind of supports for the relevant
> changes in the apiv2 modules. The other option is to regard health_monitors
> as a 'list' attribute. Which means that a POST/PUT will create/update the
> whole list. This is practical from server-side perspective, but has also
> drawbacks. Indeed it adds burden to the client; for instance, in order to
> add an element to the list you'll need a GET and then a PUT; and it also
> causes confusion because of the fact that our PUT actually implement patch
> semantics.
>
>
>
> Salvatore
>
>
>
> [1]
> http://docs.openstack.org/api/openstack-network/2.0/content/List_Networks_Detail.html#d6e858
>
>
>
> On 16 November 2012 18:04, Youcef Laribi <Youcef.Laribi at eu.citrix.com>
> wrote:
>
> Changing the subject line…
>
>
>
> Health monitors “/health_monitors/” are a top resource in the API and are
> retrieved/added/removed/updated through their CRUD operations on this top
> resource.
>
>
>
> The subresource “/pools/{pool_id}/health_monitors“ is used for associating
> already existing health monitors (created above) with an existing pool, or
> for retrieving the health monitors associated with a pool. It is a
> collection (list) that only contain IDs of health monitors not the health
> monitors themselves. We can call this resource
> “/pools/{pool_id}/health_monitor_references“ or
> “/pools/{pool_id}/pool_health_monitors” if we like, but I felt this was ugly
> and I think there is no issue or ambiguity in the definition of API itself
> as all operations are clearly described. But if you think changing its name
> helps, I can do that J Would like to hear what others in the team think.
>
>
>
> Youcef
>
>
>
> From: Oleg Bondarev [mailto:obondarev at mirantis.com]
> Sent: Friday, November 16, 2012 1:12 AM
> To: Youcef Laribi; 'OpenStack Development Mailing List'
> Subject: RE: [openstack-dev] [quantum] Quantum extension framework issue
>
>
>
> Hi guys,
>
>
>
> I just want to clarify some things regarding health monitors in LBaaS API:
> actually it is not completely a sub-resource of pool objects.
>
> According to the API it is a separate resource which can be
> added/showed/updated/deleted (with GET/POST.. “/v1.0/health_monitors/..”
> rest calls) in order to be reusable in different pools and probably anywhere
> else as Sasha mentioned. Youcef please correct me if I am wrong here.
>
> Speaking about sub-resources I think following rest call:
>
>
>
> POST /v1.0/pools/{pool_id}/health_monitors
>
>
>
> is intended to create a sub-resource of health monitor for the pool and not
> to add an existing health monitor to the pool.
>
> Also I think having health monitors as a separate resource and as a
> sub-resource of a pool at the same time is not correct.
>
> So my vision is to leave health monitors as a separate resource and to use
> member actions for the purpose of getting/associating/disassociating health
> monitors with a pool:
>
> Get health monitors of a pool:
>
> GET /v1.0/pools/{pool_id}/get_health_monitors
>
> Associate health monitors with a pool:
>
> PUT /v1.0/pools/{pool_id}/add_health_monitors
>
>
>
>
>
> {
>
>
>
>
>
> "health_monitors" : [
>
> "f3eeab00-8367-4524-b662-55e64d4cacb5"
>
> ]
>
> }
>
> Disassociate health monitors from a pool:
>
> PUT /v1.0/pools/{pool_id}/delete_health_monitors
>
> {
>
>
>
> "health_monitors" : [
>
> "f3eeab00-8367-4524-b662-55e64d4cacb5"
>
> ]
>
> }
>
>
>
> Please share your thoughts.
>
>
>
> Thanks,
>
> Oleg
>
>
>
> From: Sasha Ratkovic [mailto:sasharatkovic at juniper.net]
> Sent: Friday, November 16, 2012 3:38 AM
> To: OpenStack Development Mailing List
> Subject: Re: [openstack-dev] [quantum] Quantum extension framework issue
>
>
>
> One comment: even though health_monitor is introduced as part of LB effort,
> it has more general applicability. So having it under LB specific resource
> may pose usability problems down the road when new services are introduced,
> if health monitor is to be re-used for that purpose. One solution is to
> make it "first class" citizen with relationship to "pool" and/or make "pool"
> assume more abstract pooling semantics, reusable as well across multiple
> services in the future. (yes, I am talking about "groups" here :) ).
>
>
>
> From: Salvatore Orlando <sorlando at nicira.com>
> Reply-To: OpenStack Development Mailing List
> <openstack-dev at lists.openstack.org>
> Date: Thursday, November 15, 2012 7:40 AM
> To: OpenStack Development Mailing List <openstack-dev at lists.openstack.org>
> Subject: Re: [openstack-dev] [quantum] Quantum extension framework issue
>
>
>
> Hi Oleg,
>
>
>
> This is exactly what I was talking about.
>
> One thing you might want to consider before choosing for one direction or
> the other is that at the moment Quantum API does not use sub resources at
> all.
>
> There was a long discussion on this regard while designing the v2 API. The
> gist of the discussion was that if a resource needed sub-resources then
> there was a case for a sub-resource to become a 'first citizen' in the API.
> I am pretty sure you already have mulled over whether health_monitors should
> be a resource of their own, a sub resource of the pool, or a multi-valued
> attribute of the pool, but I wanted to give you a heads-up anyway.
>
>
>
> On your technical questions I have some answers inline.
>
>
>
> Salvatore
>
> On 15 November 2012 15:40, Oleg Bondarev <obondarev at mirantis.com> wrote:
>
> Hi folks,
>
>
>
> As Salvatore said there is a way to specify parent for a resource (see
> quantum.extensions.extensions.ResourceExtension) which allows route mapping
> for rest calls like:
>
>
>
> POST /v1.0/pools/{pool_id}/health_monitors
>
> DELETE /v1.0/pools/{pool_id}/health_monitors/{id}
>
> …
>
>
>
> In this case corresponding resource controller should be aware of resource
> parent and be able to handle CRUD operations with an additional parent_id
> parameter. Currently it doesn’t. Actually I am speaking about
> quantum.api.v2.base.Controller – so, Salvatore, do you think it is the right
> place to include sub-resource/parent handling?
>
>
>
> Working on controllers in quantum.api.v2 is the best option in my opinion.
>
> This however depends on how the route mapper associates controllers with sub
> resources. Currently, the extension framework and the core API use two
> distinct code paths: the former uses
> quantum.extensions.extensions.ExtensionMiddleware whereas the latter uses
> quantum.api.v2.router.APIRouter (this is for historical reasons only; as far
> as I can recall, there's no technical reason for this). The Extension
> Middleware has a mechanism for mapping associating parent resources to a
> mapped resource, whereas the APIRouter does not have such mechanism.
>
>
>
> As the controller does not care about how URI paths are mapped on its
> methods, the only thing we probably need to worry about is how to make sure
> that the parent resource id is passed to the controller for the
> sub-resource. To this aim, I would probably define a new controller which
> extends the base one rather than modifying quantum.api.v2.base.Controller.
>
> Btw, there is of course the hackish way of skipping base.create_resource and
> passing to ResourceExtension an object providing implementation for the
> appropriate methods. I am totally sure you're aware of this option too, but
> I would consider it only a last resort.
>
>
>
>
>
>
>
> And also how do you guys think should this improvement be done as a separate
> patch?
>
>
>
> Separate patches in these cases are always preferred.
>
>
>
>
>
> Thanks,
>
> Oleg
>
>
>
> From: Youcef Laribi [mailto:Youcef.Laribi at eu.citrix.com]
> Sent: Wednesday, November 14, 2012 11:03 PM
>
>
> To: OpenStack Development Mailing List
> Subject: Re: [openstack-dev] [quantum] Quantum extension framework issue
>
>
>
> Oleg,
>
>
>
> The “/pools/{pool_id}/health_monitors” REST resource is intended to be a
> collection sub-resource of the “/pools/{pool_id}” resource, so if the
> Quantum WSGI framework can be improved to support REST sub-resources that
> would be better and cleaner.
>
>
>
> Youcef
>
>
>
>
>
> From: Salvatore Orlando [mailto:sorlando at nicira.com]
> Sent: Wednesday, November 14, 2012 10:00 AM
> To: OpenStack Development Mailing List
> Subject: Re: [openstack-dev] [quantum] Quantum extension framework issue
>
>
>
> Hi Oleg,
>
>
>
> When I read your first email, I had the same impression as Dan.
>
> health_monitors look more like a subresource than an action.
>
>
>
> The WSGI framework at the moment is not able to manage subresources; this
> does not mean we cannot improve it though. Nevertheless, in this case the
> route mapping is not performed by the API classes in quantum/api, but by the
> extension manager. I think there should already be a way for specifying
> parent resources with extensions, but that needs to be explored.
>
>
>
> It seems however that you are now trying to map operations on health
> monitors using distinct member actions (add_health_monitor,
> get_health_monitors). This is similar to what happens with the L3 API for
> router interfaces.
>
> However, it seems the original idea behind the API design was to treat
> health_monitors as an explicit collection, which would also be probably a
> more 'restful' way of doing it. I think ultimately the question should be
> directed to Youcef and the team which contributed to the design of the LBaaS
> API.
>
> On 14 November 2012 17:18, Oleg Bondarev <obondarev at mirantis.com> wrote:
>
> Hi Dan,
>
> Thanks for your comment here.
>
> Just wanted to correct a mistake in my first email: of course there can’t be
> a dict with duplicate keys. The idea was to use list of pairs, like:
>
> member_actions = [{“health_monitors”: “GET”},
>
> {“health_monitors”: “POST”}]
>
> to have an ability of using same function name with different request
> actions. Initially I thought that the framework provides such ability but
> does not dispatch requests correctly. I was wrong.
>
> Actually there is no issue with the framework as it assumes using unique
> action names for different request methods.
>
>
>
> I believe we should update LBaaS REST API doc and use “get_health_monitors”,
> “add_health_monitors”, etc. to fit in the framework.
>
>
>
> Thanks,
>
> Oleg
>
>
>
> From: Dan Wendlandt [mailto:dan at nicira.com]
> Sent: Wednesday, November 14, 2012 7:27 PM
> To: OpenStack Development Mailing List
> Subject: Re: [openstack-dev] [quantum] Quantum extension framework issue
>
>
>
> Hi Oleg,
>
>
>
> Folks from the API-subteam can correct me, but I believe this use model is
> outside of what the API framework was trying to enable with "actions". The
> idea is that you use POST/DELETE to create an delete API "resources" (which
> actually have UUIDs, for example, the "pool" in your example below) and then
> do a PUT to an "action" to cause some kind of change that you can affect on
> a resource (e.g., "add_health_monitor" or "remove_health_monitor"). It
> sounds like what you are proposing is more treating "health_monitors" almost
> as a "sub-resource", which is not really what the "actions" stuff was
> designed for.
>
>
>
> I haven't been deeply involved in the LBaaS api design discussion though, so
> I'd also like to hear from Salvatore, et al. on the API sub-team.
>
>
>
> Dan
>
>
>
>
>
> On Wed, Nov 14, 2012 at 6:05 AM, Oleg Bondarev <obondarev at mirantis.com>
> wrote:
>
> Hi guys,
>
>
>
> While working on the API extension for LBaaS I didn’t find a way to use
> custom member actions if they have the same name and differ only by request
> method, for example
>
>
>
> List all health monitors of a specific pool: GET
> /pool/pool_id/health_monitors
>
> Associate health monitors with a pool: POST /pool/pool_id/health_monitors
>
>
>
> In quantum extension framework we pass “health_monitors” as member actions
> for a controller (quantum.api.v2.base.create_resource())
>
>
>
> member_actions = {'health_monitors': 'GET',
>
> 'health_monitors': 'POST'}
>
>
>
> controller = base.create_resource(collection_name,
>
> resource_name,
>
> plugin, params,
>
> member_actions=member_actions)
>
>
>
> According to the Controller implementation it dispatches all custom member
> actions to its plugin attr:
>
>
>
> def __getattr__(self, name):
>
> if name in self._member_actions:
>
> def _handle_action(request, id, body=None):
>
> return getattr(self._plugin, name)(request.context, id,
> body)
>
> return _handle_action
>
> else:
>
> raise AttributeError
>
>
>
> Where request.context is of type quantum.context.Context and does not
> contain info about request method.
>
> As a result there is no way to distinguish two custom actions in the plugin.
>
> Is it an issue in the framework?
>
>
>
> Possible solution may be in concatenation of request method and action name
> (“get_health_monitors”, “post_health_monitors”) in a controller before
> dispatching them to a plugin.
>
> What do you think?
>
>
>
> Thanks,
>
> Oleg
>
>
> _______________________________________________
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>
>
>
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Dan Wendlandt
>
> Nicira, Inc: www.nicira.com
>
> twitter: danwendlandt
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>
>
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