Re: [Engine-devel] RFD: API: Identifying vdsm objects in the next-gen API

From: "Adam Litke" <agl(a)us.ibm.com&gt; To: "Saggi Mizrahi" <smizrahi(a)redhat.com&gt; Cc: engine-devel(a)linode01.ovirt.org, "Dan Kenigsberg" <danken(a)redhat.com&gt;, "Federico Simoncelli" <fsimonce(a)redhat.com&gt;, "Ayal Baron" <abaron(a)redhat.com&gt;, vdsm-devel(a)lists.fedorahosted.org Sent: Thursday, November 29, 2012 5:22:43 PM Subject: Re: RFD: API: Identifying vdsm objects in the next-gen API On Thu, Nov 29, 2012 at 04:52:14PM -0500, Saggi Mizrahi wrote: > They are not future proof as the paradigm is completely different. > Storage > domain IDs are not static any more (and are not guaranteed to be > unique or the > same across the cluster. Image IDs represent the ID of the > projected data and > not the actual unique path. Just as an example, to run a VM you > give a list > of domains that might contain the needed images in the chain and > the image ID > of the tip. The paradigm is changed to and most calls get non > synchronous > number of images and domains. Further more, the APIs themselves > are > completely different. So future proofing is not really an issue. I don't understand this at all. Perhaps we could all use some education on the architecture of the planned architectural changes. If I can pass an arbitrary list of domainIDs that _might_ contain the data, why wouldn't I just pass all of them every time? In that case, why are they even required since vdsm would have to search anyway?

> As to making the current API a bit simpler. As I said, making them > opaque is > problematic as currently the engine is responsible for creating the > IDs. As I mentioned in my last post, engine still can specify the ID's when the object is first created. From that point forward the ID never changes so it can be baked into the identifier.

> Further more, some calls require you to play with these (making a > template > instead of a snapshot). Also, the full chain and topology needs to > be > completely visible to the engine. Please provide a specific example of how you play with the IDs. I can guess where you are going, but I don't want to divert the thread.

> These things, as you said, are problematic. But this is the way > things are > today. We are changing them.

> As for task IDs. Currently task IDs are only used for storage and > they get > persisted to disk. This is WRONG and is not the case with the new > storage API. > Because we moved to an asynchronous message based protocol > (json-rpc over > TCP\AMQP) there is no need to generate a task ID. it is built in to > json-rpc. > json-rpc specifies that the IDs have to be unique for a client as > long as the > request is still active. This is good enough as internally we can > have a verb > for a client to query it's own running tasks and a verb to query > other host > tasks by mangling in the client before the ID. Because the > protocol is So this would rely on the client keeping the connection open and as soon as it disconnects it would lose the ability to query tasks from before the connection went down? I don't know if it's a good idea to conflate message ID's with task ID's. While the protocol can operate asynchronously, some calls have synchronous semantics and others have asynchronous semantics. I would expect sync calls to return their data immediately and async calls to return immediately with either: an error code, or an 'operation started' message and associated ID for querying the status of the operation.

> asynchronous all calls are asynchronous by nature well. Tasks will > no longer > be persisted or expected to be persisted. It's the callers > responsibility to > query the state and see if the operation succeeded or failed if the > caller or > VDSM died in the middle of the call. The current "cleanTask()" > system can't be > used when more then one client is using VDSM and will not be used > for anything > other then legacy storage. I agree about not persisting tasks in the future. Although I think finished tasks should remain in memory for some time so they can be queried by a client who must reconnect.

> AFAIK Apart from storage all objects IDs are constructed with a > single ID, > name or alias. VMs, storageConnections, network interfaces. So it's > not a real > issue. I agree that in the future we should keep the idiom of pass > configuration once, name it, and keep using the name to reference > the object. Yes, storage is the major problem here.

> ----- Original Message ----- > > From: "Adam Litke" <agl(a)us.ibm.com&gt; > > To: "Saggi Mizrahi" <smizrahi(a)redhat.com&gt; > > Cc: engine-devel(a)linode01.ovirt.org, "Dan Kenigsberg" > > <danken(a)redhat.com&gt;, "Federico Simoncelli" > > <fsimonce(a)redhat.com&gt;, "Ayal Baron" <abaron(a)redhat.com&gt;, > > vdsm-devel(a)lists.fedorahosted.org > > Sent: Thursday, November 29, 2012 4:18:40 PM > > Subject: Re: RFD: API: Identifying vdsm objects in the next-gen > > API > > > > On Thu, Nov 29, 2012 at 02:16:42PM -0500, Saggi Mizrahi wrote: > > > This is all only valid for the current storage API the new one > > > doesn't have > > > pools or volumes. Only domains and images. Also, images and > > > domains are more > > > loosely coupled and make this method problematic. > > > > I am looking for an incremental way to bridge the differences. > > It's > > been 2 > > years and we still don't have the revamped storage API so I am > > planning on what > > we have being around for awhile :) I think that defining object > > identifiers as > > opaque structured types is also future proof. In the future an > > Image-ng object > > we can drop 'storagepoolID' from the identifier and, if it makes > > sense, remove > > the hard association with a storageDomain as well. The point > > behind > > this > > refactoring is to give us the option of coupling multiple UUID's > > (or > > other data) > > to form a single, opaque identifier. > > > > > That being said, if we do choose to make the current storage > > > API > > > officially > > > supported I do agree that it looks a bit simpler but for the > > > price > > > of forcing > > > the user to construct these objects before sending the request. > > > I > > > know for a > > > fact that the engine will just create these objects on the fly > > > because they > > > use their own objects to group things logically. This means > > > adding > > > more work > > > instead of removing it. Most clients will do that anyway as > > > they > > > will use > > > their own DAL to store these relationships. > > > > > > > Thanks for bringing up some of these points. All deserve > > attention > > so I will > > address each one individually: > > > > The current API does not yet make an official statement of > > support > > for anything. > > I want to model the current storage API so that the node level > > API > > can have the > > same level of functionality as is currently supported. I am all > > for > > removing > > deprecated functions and redesigning in-place for a reasonable > > amount > > of time > > going forward. In a perfect world, libvdsm-1.0 would release > > with no > > mention of > > storage pools at all. > > > > If properly designed, the end-user (including engine) would never > > be > > constructing these objects itself. Object identifiers are > > essentially opaque > > structures. In order to make this possible, we need to make sure > > that the API > > provides all of the functions needed to lookup objects. So far > > these > > are: > > > > StoragePool: Host.getConnectedStoragePools > > StorageDomain: Host.getStorageDomains > > Image: StorageDomain.getImages > > Volume: StorageDomain.getVolumes / Image.getVolumes > > VM: Host.getVMList > > Task: Host.getAllTasks > > > > All of the above would return object identifiers. > > > > The other case is for creation of new resources. In that case, > > the > > create > > method needs to move to the owning object. The key example is > > VM.create which > > should move to Host.createVM. Functions such as Host.createVM > > could > > still > > accept a vmUUID (because I assume engine does want the ability to > > set > > this > > explicitly). However, they should be changed to return either a > > TaskIdentifier > > (if the creation is asynchronous) or a *Identifier (eg. > > VmIdentifier) > > if the > > object was created synchronously. > > > > All told, I think the net is less work for clients. They will no > > longer need to > > model the object associations and relationships because the API > > will > > take care > > of that automatically. > > > > > ----- Original Message ----- > > > > From: "Adam Litke" <agl(a)us.ibm.com&gt; > > > > To: vdsm-devel(a)lists.fedorahosted.org > > > > Cc: engine-devel(a)linode01.ovirt.org, "Dan Kenigsberg" > > > > <danken(a)redhat.com&gt;, "Federico Simoncelli" > > > > <fsimonce(a)redhat.com&gt;, "Saggi Mizrahi" <smizrahi(a)redhat.com&gt;, > > > > "Ayal Baron" <abaron(a)redhat.com&gt; > > > > Sent: Thursday, November 29, 2012 12:19:06 PM > > > > Subject: RFD: API: Identifying vdsm objects in the next-gen > > > > API > > > > > > > > Today in vdsm, every object (StoragePool, StorageDomain, VM, > > > > Volume, > > > > etc) is > > > > identified by a single UUID. On the surface, it seems like > > > > this > > > > is > > > > enough info > > > > to properly identify a resource but in practice it's not. > > > > For > > > > example, when you > > > > look at the API's dealing with Volumes, almost all of them > > > > require an > > > > sdUUID, > > > > spUUID, and imgUUID in order to provide proper context for > > > > the > > > > operation. > > > > > > > > Needing to provide these extra UUIDs is a burden on the API > > > > user > > > > because knowing > > > > which values to pass requires internal knowledge of the API. > > > > For > > > > example, the > > > > spUUID parameter is almost always just the connected storage > > > > pool. > > > > Since we > > > > know there can currently be only one connected pool, the > > > > value is > > > > known. > > > > > > > > I would like to move away from needing to understand all of > > > > these > > > > relationships > > > > from the end user perspective by encapsulating the extra > > > > context > > > > into > > > > new object > > > > identifier types as follows: > > > > > > > > StoragePoolIdentifier: > > > > { 'storagepoolID': 'UUID' } > > > > StorageDomainIdentifier: > > > > { 'storagepoolID*': 'UUID', 'storagedomainID': 'UUID' } > > > > ImageIdentifier: > > > > { 'storagepoolID*': 'UUID', 'storagedomainID': 'UUID', > > > > 'imageID': > > > > 'UUID' } > > > > VolumeIdentifier: > > > > { 'storagepoolID*': 'UUID', 'storagedomainID': 'UUID', > > > > 'imageID': 'UUID', 'volumeID': 'UUID' } > > > > TaskIdentifier: > > > > { 'taskID': 'UUID' } > > > > VMIdentifier: > > > > { 'vmID': 'UUID' } > > > > > > > > In the new API, anytime a reference to an object is required, > > > > one > > > > of > > > > the above > > > > structures must be passed in place of today's single UUID. > > > > In > > > > many > > > > cases, this > > > > will allow us to reduce the number of parameters to the > > > > function > > > > since the > > > > needed contextual parameters (spUUID, etc) will be part of > > > > the > > > > object's > > > > identifier. Similarly, any time the API returns an object > > > > reference > > > > it would > > > > return a *Identifier instead of a bare UUID. > > > > > > > > These identifier types are basically opaque blobs to the API > > > > users > > > > and are only > > > > ever generated by vdsm itself. Because of this, we can > > > > change > > > > the > > > > internal > > > > structure of the identifier to require new information or > > > > (before > > > > freezing the > > > > API) remove fields that no longer make sense. > > > > > > > > I would greatly appreciate your comments on this proposal. > > > > If it > > > > seems > > > > reasonable, I will revamp the current schema to make the > > > > necessary > > > > changes and > > > > provide the Bridge patch functions to convert between the > > > > current > > > > implementation > > > > and the new schema. > > > > > > > > --- sample schema patch --- > > > > > > > > commit 48f6b0f0a111dd0b372d211a4e566ce87f375cee > > > > Author: Adam Litke <agl(a)us.ibm.com&gt; > > > > Date: Tue Nov 27 14:14:06 2012 -0600 > > > > > > > > schema: Introduce class identifier types > > > > > > > > When calling API methods that belong to a particular > > > > class, a > > > > class instance > > > > must be indicated by passing a set of identifiers in the > > > > request. > > > > The location > > > > of these parameters within the request is: 'params' -> > > > > '__obj__'. > > > > Since this > > > > set of identifiers must be used together to correctly > > > > instantiate > > > > an object, it > > > > makes sense to define these as proper types within the > > > > API. > > > > Then, functions > > > > that return an object (or list of objects) can refer to > > > > the > > > > correct type. > > > > > > > > Signed-off-by: Adam Litke <agl(a)us.ibm.com&gt; > > > > > > > > diff --git a/vdsm_api/vdsmapi-schema.json > > > > b/vdsm_api/vdsmapi-schema.json > > > > index 0418e6e..7e2e851 100644 > > > > --- a/vdsm_api/vdsmapi-schema.json > > > > +++ b/vdsm_api/vdsmapi-schema.json > > > > @@ -937,7 +937,7 @@ > > > > # Since: 4.10.0 > > > > ## > > > > {'command': {'class': 'Host', 'name': > > > > 'getConnectedStoragePools'}, > > > > - 'returns': ['StoragePool']} > > > > + 'returns': ['StoragePoolIdentifier']} > > > > > > > > ## > > > > # @BlockDeviceType: > > > > @@ -1572,7 +1572,7 @@ > > > > {'command': {'class': 'Host', 'name': 'getStorageDomains'}, > > > > 'data': {'*storagepoolID': 'UUID', '*domainClass': > > > > 'StorageDomainImageClass', > > > > '*storageType': 'StorageDomainType', > > > > '*remotePath': > > > > 'str'}, > > > > - 'returns': ['StorageDomain']} > > > > + 'returns': ['StorageDomainIdentifier']} > > > > > > > > ## > > > > # @Host.getStorageRepoStats: > > > > @@ -2406,7 +2406,7 @@ > > > > ## > > > > {'command': {'class': 'Host', 'name': 'getVMList'}, > > > > 'data': {'*vmList': ['UUID']}, > > > > - 'returns': ['VM']} > > > > + 'returns': ['VMIdentifier']} > > > > > > > > ## > > > > # @Host.ping: > > > > @@ -2744,10 +2744,11 @@ > > > > 'returns': 'ConnectionRefMap'} > > > > > > > > ## Category: @ISCSIConnection > > > > ################################################## > > > > + > > > > ## > > > > -# @ISCSIConnection: > > > > +# @ISCSIConnectionIdentifier: > > > > # > > > > -# ISCSIConnection API object. > > > > +# Identifier for an ISCSIConnection object. > > > > # > > > > # @host: A fully-qualified domain name (FQDN) or IP > > > > address > > > > # > > > > @@ -2757,11 +2758,21 @@ > > > > # > > > > # @password: #optional The password associated with the > > > > given > > > > username > > > > # > > > > -# Since: 4.10.0 > > > > +# Since: 4.10.1 > > > > +## > > > > +{'type': 'ISCSIConnectionIdentifier', > > > > + 'data': {'host': 'str', 'port': 'int', '*user': 'str', > > > > '*password': > > > > 'str'}} > > > > + > > > > +## > > > > +# @ISCSIConnection: > > > > +# > > > > +# ISCSIConnection API object. > > > > +# > > > > +# @ident: The object identifier > > > > +# > > > > +# Since: 4.10.1 > > > > ## > > > > -{'class': 'ISCSIConnection', > > > > - 'data': {'host': 'str', 'port': 'int', '*user': 'str', > > > > - '*password': 'str'}} > > > > +{'class': 'ISCSIConnection', 'ident': > > > > 'ISCSIConnectionIdentifier'} > > > > > > > > ## > > > > # @ISCSIConnection.discoverSendTargets: > > > > @@ -2777,10 +2788,11 @@ > > > > 'returns': ['str']} > > > > > > > > ## Category: @Image > > > > ############################################################ > > > > + > > > > ## > > > > -# @Image: > > > > +# @ImageIdentifier: > > > > # > > > > -# Image API object. > > > > +# Identifier for an Image object. > > > > # > > > > # @imageID: The UUID of the Image > > > > # > > > > @@ -2788,13 +2800,24 @@ > > > > # > > > > # @storagedomainID: The UUID of the Storage Domain > > > > associated > > > > with > > > > the Image > > > > # > > > > -# Since: 4.10.0 > > > > +# Since: 4.10.1 > > > > ## > > > > -{'class': 'Image', > > > > +{'type': 'ImageIdentifier', > > > > 'data': {'imageID': 'UUID', 'storagepoolID': 'UUID', > > > > 'storagedomainID': 'UUID'}} > > > > > > > > ## > > > > +# @Image: > > > > +# > > > > +# Image API object. > > > > +# > > > > +# @ident: The object identifier > > > > +# > > > > +# Since: 4.10.1 > > > > +## > > > > +{'class': 'Image', 'ident': 'ImageIdentifier'} > > > > + > > > > +## > > > > # @Image.delete: > > > > # > > > > # Delete the Image and all of its Volumes. > > > > @@ -2843,7 +2866,7 @@ > > > > # Since: 4.10.0 > > > > ## > > > > {'command': {'class': 'Image', 'name': 'getVolumes'}, > > > > - 'returns': ['Volume']} > > > > + 'returns': ['VolumeIdentifier']} > > > > > > > > ## > > > > # @Image.mergeSnapshots: > > > > @@ -2905,17 +2928,26 @@ > > > > > > > > ## Category: @LVMVolumeGroup > > > > ################################################### > > > > ## > > > > +# @LVMVolumeGroupIdentifier: > > > > +# > > > > +# An identifier for a LVMVolumeGroup object. > > > > +# > > > > +# @lvmvolumegroupID: The volume group UUID > > > > +# > > > > +# Since: 4.10.1 > > > > +## > > > > +{'type': 'LVMVolumeGroupIdentifier', 'data': > > > > {'lvmvolumegroupID': > > > > 'UUID'}} > > > > + > > > > +## > > > > # @LVMVolumeGroup: > > > > # > > > > # LVMVolumeGroup API object. > > > > # > > > > -# @lvmvolumegroupID: #optional Associate this object with > > > > an > > > > existing LVM > > > > -# Volume Group > > > > +# @ident: The object identifier > > > > # > > > > -# Since: 4.10.0 > > > > +# Since: 4.10.1 > > > > ## > > > > -{'class': 'LVMVolumeGroup', > > > > - 'data': {'lvmvolumegroupID': 'UUID'}} > > > > +{'class': 'LVMVolumeGroup', 'ident': > > > > 'LVMVolumeGroupIdentifier'} > > > > > > > > ## > > > > # @LVMVolumeGroup.create: > > > > @@ -2964,21 +2996,32 @@ > > > > > > > > ## Category: @StorageDomain > > > > #################################################### > > > > ## > > > > -# @StorageDomain: > > > > +# @StorageDomainIdentifier: > > > > # > > > > -# StorageDomain API object. > > > > +# An identifier for a StorageDomain object. > > > > # > > > > # @storagedomainID: Associate this object with a new or > > > > existing > > > > Storage Domain > > > > # > > > > # @storagepoolID: #optional The Storage Pool UUID if this > > > > Storage > > > > Domain is > > > > # attached > > > > # > > > > -# Since: 4.10.0 > > > > +# Since: 4.10.1 > > > > ## > > > > -{'class': 'StorageDomain', > > > > +{'type': 'StorageDomainIdentifier', > > > > 'data': {'storagedomainID': 'UUID', 'storagepoolID': > > > > 'UUID'}} > > > > > > > > ## > > > > +# @StorageDomain: > > > > +# > > > > +# StorageDomain API object. > > > > +# > > > > +# @ident: The object identifier > > > > +# > > > > +# Since: 4.10.1 > > > > +## > > > > +{'class': 'StorageDomain', 'ident': > > > > 'StorageDomainIdentifier'} > > > > + > > > > +## > > > > # @StorageDomain.activate: > > > > # > > > > # Activate an attached but inactive Storage Domain. > > > > @@ -3184,7 +3227,7 @@ > > > > # Since: 4.10.0 > > > > ## > > > > {'command': {'class': 'StorageDomain', 'name': 'getImages'}, > > > > - 'returns': ['Image']} > > > > + 'returns': ['ImageIdentifier']} > > > > > > > > ## > > > > # @StorageDomainRole: > > > > @@ -3295,7 +3338,7 @@ > > > > ## > > > > {'command': {'class': 'StorageDomain', 'name': > > > > 'getVolumes'}, > > > > 'data': {'imageID': 'UUID'}, > > > > - 'returns': ['Volume']} > > > > + 'returns': ['VolumeIdentifier']} > > > > > > > > ## > > > > # @StorageDomain.setDescription: > > > > @@ -3355,15 +3398,26 @@ > > > > > > > > ## Category: @StoragePool > > > > ###################################################### > > > > ## > > > > +# @StoragePoolIdentifier: > > > > +# > > > > +# An identifier for a StoragePool object. > > > > +# > > > > +# @storagepoolID: Associate this object with a new or > > > > existing > > > > Storage Pool > > > > +# > > > > +# Since: 4.10.1 > > > > +## > > > > +{'type': 'StoragePoolIdentifier', 'data': {'storagepoolID': > > > > 'UUID'}} > > > > + > > > > +## > > > > # @StoragePool: > > > > # > > > > # StoragePool API object. > > > > # > > > > -# @storagepoolID: Associate this object with a new or > > > > existing > > > > Storage Pool > > > > +# @ident: The object identifier > > > > # > > > > -# Since: 4.10.0 > > > > +# Since: 4.10.1 > > > > ## > > > > -{'class': 'StoragePool', 'data': {'storagepoolID': 'UUID'}} > > > > +{'class': 'StoragePool', 'ident': 'StoragePoolIdentifier'} > > > > > > > > ## > > > > # @StoragePool.connect: > > > > @@ -3629,7 +3683,7 @@ > > > > ## > > > > {'command': {'class': 'StoragePool', 'name': > > > > 'getDomainsContainingImage'}, > > > > 'data': {'imageID': 'UUID', '*onlyDataDomains': 'bool'}, > > > > - 'returns': ['StorageDomain']} > > > > + 'returns': ['StorageDomainIdentifier']} > > > > > > > > ## > > > > # @StoragePool.getIsoList: > > > > @@ -4058,15 +4112,27 @@ > > > > > > > > ## Category: @Task > > > > ############################################################# > > > > ## > > > > +# @TaskIdentifier: > > > > +# > > > > +# An identifier for a Task object. > > > > +# > > > > +# @taskID: The task UUID > > > > +# > > > > +# Since: 4.10.1 > > > > +## > > > > +{'type': 'TaskIdentifier', 'data': {'taskID': 'UUID'}} > > > > + > > > > + > > > > +## > > > > # @Task: > > > > # > > > > # Task API object. > > > > # > > > > -# @taskID: Associate this object with an existing Task > > > > +# @ident: The object identifier > > > > # > > > > -# Since: 4.10.0 > > > > +# Since: 4.10.1 > > > > ## > > > > -{'class': 'Task', 'data': {'taskID': 'UUID'}} > > > > +{'class': 'Task', 'ident': 'TaskIdentifier'} > > > > > > > > ## > > > > # @Task.clear: > > > > @@ -4123,15 +4189,26 @@ > > > > > > > > ## Category: @VM > > > > ############################################################### > > > > ## > > > > +# @VMIdentifier: > > > > +# > > > > +# An identifier for a VM object. > > > > +# > > > > +# @vmID: The task UUID > > > > +# > > > > +# Since: 4.10.1 > > > > +## > > > > +{'type': 'VMIdentifier', 'data': {'vmID': 'UUID'}} > > > > + > > > > +## > > > > # @VM: > > > > # > > > > # VM API object. > > > > # > > > > -# @vmID: Associate this object with an existing VM > > > > +# @ident: The object identifier > > > > # > > > > -# Since: 4.10.0 > > > > +# Since: 4.10.1 > > > > ## > > > > -{'class': 'VM', 'data': {'vmID': 'UUID'}} > > > > +{'class': 'VM', 'ident': 'VMIdentifier'} > > > > > > > > ## > > > > # @DriveSpecVolume: > > > > @@ -5161,9 +5238,9 @@ > > > > > > > > ## Category: @Volume > > > > ########################################################### > > > > ## > > > > -# @Volume: > > > > +# @VolumeIdentifier: > > > > # > > > > -# Volume API object. > > > > +# An identifier for a Volume object. > > > > # > > > > # @volumeID: The UUID of the Volume > > > > # > > > > @@ -5173,13 +5250,24 @@ > > > > # > > > > # @imageID: The Image associated with @UUID > > > > # > > > > -# Since: 4.10.0 > > > > +# Since: 4.10.1 > > > > ## > > > > -{'class': 'Volume', > > > > +{'type': 'VolumeIdentifier', > > > > 'data': {'volumeID': 'UUID', 'storagepoolID': 'UUID', > > > > 'storagedomainID': 'UUID', 'imageID': 'UUID'}} > > > > > > > > ## > > > > +# @Volume: > > > > +# > > > > +# Volume API object. > > > > +# > > > > +# @ident: The object identifier > > > > +# > > > > +# Since: 4.10.1 > > > > +## > > > > +{'class': 'Volume', 'ident': 'VolumeIdentifier'} > > > > + > > > > +## > > > > # @VolumeRole: > > > > # > > > > # An enumeration of Volume Roles. > > > > > > > > -- > > > > Adam Litke <agl(a)us.ibm.com&gt; > > > > IBM Linux Technology Center > > > > > > > > > > > > > > > -- > > Adam Litke <agl(a)us.ibm.com&gt; > > IBM Linux Technology Center > > > > > -- Adam Litke <agl(a)us.ibm.com&gt; IBM Linux Technology Center