Recently we've had some very productive discussions concerning the VDSM API. I want to attempt to refocus the discussion around an emerging proposal and see if we can agree on a sensible path forward. Based on the discussion, I have identified the following requirements that a new API for vdsm should have: 1.) Single API that can be consumed by ovirt-engine and ISVs - We don't want to maintain multiple parallel APIs - To develop a vendor ecosystem, we must have a robust external API to vdsm

A single-node (or standalone VDSM deployment) is a very important use case. Many people are coming into the oVirt community from different perspectives. The strength of the ecosystem depends, in part, on the ability of oVirt components to be combined in unique ways with other software to produce solutions. The complete oVirt stack is a great thing, but not the only way to use the technology.

On 12/01/2011 07:35 PM, Adam Litke wrote: > A single-node (or standalone VDSM deployment) is a very important use case. > Many people are coming into the oVirt community from different perspectives. > The strength of the ecosystem depends, in part, on the ability of oVirt > components to be combined in unique ways with other software to produce > solutions. The complete oVirt stack is a great thing, but not the only way to > use the technology. Just out of curiosity: what might those single node cases be, outside implementing an oVirt like solution?

I think understanding those better is also critical input to the API design. Regards, Geert _______________________________________________ vdsm-devel mailing list vdsm-devel(a)lists.fedorahosted.org https://fedorahosted.org/mailman/listinfo/vdsm-devel

* Geert Jansen <gjansen(a)redhat.com&gt; [2011-11-30 17:38]: > Hi, > > i think this makes sense, but i'm not a VDSM expert. I did want to > point > out one other point, below: > > On 11/30/2011 11:40 PM, Adam Litke wrote: > > Recently we've had some very productive discussions concerning > > the VDSM API. I > > want to attempt to refocus the discussion around an emerging > > proposal and see if > > we can agree on a sensible path forward. > > > > Based on the discussion, I have identified the following > > requirements that > > a new API for vdsm should have: > > > > 1.) Single API that can be consumed by ovirt-engine and ISVs > > - We don't want to maintain multiple parallel APIs > > - To develop a vendor ecosystem, we must have a robust external > > API to > > vdsm > > I have doubts around how useful the VDSM API will be for creating > an > ecosystem. If you look at most virtualization ISVs today, they want > to > integrate with a multi-node API and not a single-node API. The only > use > case that i know where integrating with a single node API is > requested > is when you're basically creating a virtualization management > platform > like oVirt itself. Without a first-class node level API, we're precluding the very case you're aware of. If we're building a community and ecosystem around KVM management then we need to be open to someone building that management platform and doing it in a way that keeps things compatible. There are existing products (IBM has a number in this space) which utilize libvirt as a node-level API which won't be able to (easily) integrate all of oVirt just to obtain access to the nodes. Further, if the only way to consume VDSM is via the multi-node solution, then price of entry is a much larger, more complex stack with more dependencies. This raises the barrier of entry and participation. IMHO, not ideal when we're attempting to grow a community. Alternatively, if we enable a common node API, not only do we support single node deployments (think virtual appliances, or hardware appliances; IBM has a few of these) but allowing competing (but compatible) multi-node/cluster solutions; and it even supports the single node solutions to be managed by different kvm-based management platforms because they're all working with the same node-level API. Having a first-class node API is a critical starting point for building our larger kvm management community since it allows for easier integration of existing products. I cannot stress that point enough; if we're committed to being an open community then we need design our interfaces to encourage participation. Lowing the cost of participation and integrate is great way to enable an ecosystem.

-- Ryan Harper Software Engineer; Linux Technology Center IBM Corp., Austin, Tx ryanh(a)us.ibm.com _______________________________________________ vdsm-devel mailing list vdsm-devel(a)lists.fedorahosted.org https://fedorahosted.org/mailman/listinfo/vdsm-devel

> -----Original Message----- > From: Adam Litke [mailto:agl@us.ibm.com] > Sent: Thursday, December 01, 2011 0:41 AM > To: vdsm-devel(a)lists.fedorahosted.org; engine-devel(a)ovirt.org > Cc: Daniel P. Berrange; Chris Wright; Dan Kenigsberg; Itamar Heim > Subject: Proposed next-generation vdsm API > > Recently we've had some very productive discussions concerning the > VDSM API. I > want to attempt to refocus the discussion around an emerging > proposal and see if > we can agree on a sensible path forward. > > Based on the discussion, I have identified the following > requirements that > a new API for vdsm should have: > > 1.) Single API that can be consumed by ovirt-engine and ISVs > - We don't want to maintain multiple parallel APIs > - To develop a vendor ecosystem, we must have a robust external > API to > vdsm > > 2.) Full vdsm capabilities are exposed without requiring > ovirt-engine > - ovirt components should be modular and independently useful > - Some deployments might want to manage nodes without ovirt-engine > > 3.) Standardized protocol with low overhead > - Required for widespread adoption > > 4.) Support for asynchronous tasks and events > - Needed by ovirt-engine and other consumers > > Based on these requirements, the following proposal has started to emerge: > > Create a REST API that will provide all of the functionality that > is currently > available via the xmlrpc interface (with the goal of deprecating > xmlrpc once it > becomes mature enough). To support advanced clustering features > that > ovirt-engine is planning, we'll write an QMF broker that can proxy > the REST API > onto a message bus. ovirt-engine will interact with vdsm > exclusively over this > bus but the REST API will be the principle API and the entry point > for ISV apps. > A REST API provides a light-weight and standard way to access all > of the vdsm > functionality. > > The REST API will handle events by exposing a new 'events' > collection at the api > root. REST users will use some sort of polling to collect these > events. The > details of this interface are being worked on. Several ways for minimizing the > impact of polling have been discussed. The QMF broker can expose a > publish/subscribe model for events as appropriate. > > Is this model an acceptable way to improve the vdsm API? I would > like to hear > the opinions of ovirt-engine developers, vdsm developers, and other > stakeholders. Thanks for providing feedback on this proposal! Why things non native to REST and wrap it in QMF, rather than do the reverse? Or just to them in parallel, since it sounds like both are going to be first class citizens?

_______________________________________________ vdsm-devel mailing list vdsm-devel(a)lists.fedorahosted.org https://fedorahosted.org/mailman/listinfo/vdsm-devel

On Thu, Dec 01, 2011 at 02:02:27AM -0500, Ayal Baron wrote: > > > ----- Original Message ----- > > > > > > > -----Original Message----- > > > From: Adam Litke [mailto:agl@us.ibm.com] > > > Sent: Thursday, December 01, 2011 0:41 AM > > > To: vdsm-devel(a)lists.fedorahosted.org; engine-devel(a)ovirt.org > > > Cc: Daniel P. Berrange; Chris Wright; Dan Kenigsberg; Itamar > > > Heim > > > Subject: Proposed next-generation vdsm API > > > > > > Recently we've had some very productive discussions concerning > > > the > > > VDSM > > API. I > > > want to attempt to refocus the discussion around an emerging > > > proposal > > and see if > > > we can agree on a sensible path forward. > > > > > > Based on the discussion, I have identified the following > > > requirements > > that > > > a new API for vdsm should have: > > > > > > 1.) Single API that can be consumed by ovirt-engine and ISVs > > > - We don't want to maintain multiple parallel APIs > > > - To develop a vendor ecosystem, we must have a robust > > > external > > > API to > > > vdsm > > > > > > 2.) Full vdsm capabilities are exposed without requiring > > > ovirt-engine > > > - ovirt components should be modular and independently useful > > > - Some deployments might want to manage nodes without > > > ovirt-engine > > > > > > 3.) Standardized protocol with low overhead > > > - Required for widespread adoption > > > > > > 4.) Support for asynchronous tasks and events > > > - Needed by ovirt-engine and other consumers > > > > > > Based on these requirements, the following proposal has started > > > to > > emerge: > > > > > > Create a REST API that will provide all of the functionality > > > that > > > is > > currently > > > available via the xmlrpc interface (with the goal of > > > deprecating > > > xmlrpc > > once it > > > becomes mature enough). To support advanced clustering > > > features > > > that > > > ovirt-engine is planning, we'll write an QMF broker that can > > > proxy > > > the > > REST API > > > onto a message bus. ovirt-engine will interact with vdsm > > > exclusively > > over this > > > bus but the REST API will be the principle API and the entry > > > point > > > for > > ISV apps. > > > A REST API provides a light-weight and standard way to access > > > all > > > of the > > vdsm > > > functionality. > > > > > > The REST API will handle events by exposing a new 'events' > > > collection at > > the api > > > root. REST users will use some sort of polling to collect > > > these > > > events. > > The > > > details of this interface are being worked on. Several ways > > > for > > minimizing the > > > impact of polling have been discussed. The QMF broker can > > > expose a > > > publish/subscribe model for events as appropriate. > > > > > > Is this model an acceptable way to improve the vdsm API? I > > > would > > > like > > to hear > > > the opinions of ovirt-engine developers, vdsm developers, and > > > other > > > stakeholders. Thanks for providing feedback on this proposal! > > > > Why things non native to REST and wrap it in QMF, rather than do > > the > > reverse? > > Or just to them in parallel, since it sounds like both are going > > to > > be > > first class citizens? > > This was more my understanding from our discussion on IRC > yesterday. I'm afraid I did not follow that discussion to your conclusions... > REST API - everything that is relevant for single node management > QMF - same API as above + multi-node relevant API calls. I don't > see any > reason for doing weird things over REST to support the latter. A QMF broker runs on the vdsm host and talks to the REST API. It connects to a bus and exposes an API to ovirt-engine on this bus using a vdsm-base schema. ovirt-engine wants additional clustering functionality. This API should be implemented completely between the QMF broker and ovirt-engine using a separate vdsm-cluster schema. > In fact, I don't even see any real reason for going through the > REST API when > using QMF. Because we want to avoid the proliferation of APIs. I would prefer a mostly vertical chain of API components to a vdsm with several independent APIs (which are sure to diverge or be neglected by individual developers/patches). > If you take a look at today's API you will see that there is > nothing there > that limits it to XML-RPC and we could easily expose all the calls > using REST > or anything else. In python, exposing a new verb in the various > APIs can be > automatic so this would require very little maintenance. Any > multi-node or > transport specific calls can be decorated as such and would be > automatically > ignored/picked up by the relevant API layer. This way, we could > also easily > enable using different bus protocols assuming a customer already > has a > deployment as was suggested yesterday. I don't think this will be as automatic as you suggest in practice. It sounds like it will increase code complexity, obfuscation, and maintenance burden.

-- Adam Litke <agl(a)us.ibm.com&gt; IBM Linux Technology Center

Recently we've had some very productive discussions concerning the VDSM API. I want to attempt to refocus the discussion around an emerging proposal and see if we can agree on a sensible path forward. Based on the discussion, I have identified the following requirements that a new API for vdsm should have: 1.) Single API that can be consumed by ovirt-engine and ISVs - We don't want to maintain multiple parallel APIs - To develop a vendor ecosystem, we must have a robust external API to vdsm 2.) Full vdsm capabilities are exposed without requiring ovirt-engine - ovirt components should be modular and independently useful - Some deployments might want to manage nodes without ovirt-engine 3.) Standardized protocol with low overhead - Required for widespread adoption 4.) Support for asynchronous tasks and events - Needed by ovirt-engine and other consumers Based on these requirements, the following proposal has started to emerge: Create a REST API that will provide all of the functionality that is currently available via the xmlrpc interface

(with the goal of deprecating xmlrpc once it becomes mature enough). To support advanced clustering features that ovirt-engine is planning, we'll write an QMF broker that can proxy the REST API onto a message bus. ovirt-engine will interact with vdsm exclusively over this bus but the REST API will be the principle API and the entry point for ISV apps. A REST API provides a light-weight and standard way to access all of the vdsm functionality. The REST API will handle events by exposing a new 'events' collection at the api root. REST users will use some sort of polling to collect these events. The details of this interface are being worked on. Several ways for minimizing the impact of polling have been discussed. The QMF broker can expose a publish/subscribe model for events as appropriate. Is this model an acceptable way to improve the vdsm API? I would like to hear the opinions of ovirt-engine developers, vdsm developers, and other stakeholders. Thanks for providing feedback on this proposal!