[Gluster-devel] [Heketi] Block store related API design discussion

Raghavendra Talur rtalur at redhat.com
Tue Sep 13 05:38:44 UTC 2016

On Mon, Sep 12, 2016 at 11:30 PM, Prasanna Kalever <pkalever at redhat.com>

> Hi all,
> This mail is open for discussion on gluster block store integration with
> heketi and its REST API interface design constraints.
>                          ___ Volume Request ...
>                         |
>                         |
> PVC claim -> Heketi --->|
>                         |
>                         |
>                         |
>                         |
>                         |                            __ BlockCreate
>                         |                           |
>                         |                           |__ BlockInfo
>                         |                           |
>                         |___ Block Request (APIS)-> |__ BlockResize
>                                                     |
>                                                     |__ BlockList
>                                                     |
>                                                     |__ BlockDelete
> Heketi will have block API and volume API, when user submit a Persistent
> volume claim, Kubernetes provisioner based on the storage class(from PVC)
> talks to heketi for storage, heketi intern calls block or volume API's
> based on request.

This is probably wrong. It won't be Heketi calling block or volume APIs. It
would be Kubernetes calling block or volume API *of* Heketi.

> With my limited understanding, heketi currently creates clusters from
> provided nodes, creates volumes and handover them to the user.
> For block related API's, it has to deal with files right ?
> Here is how block API's look like in short-
> Create: heketi has to create file in the volume and export it as a iscsi
> target device and hand it over to user.
> Info: show block stores information across all the clusters, connection
> info, size etc.
> resize: resize the file in the volume, refresh connections from initiator
> side
> List: List the connections
> Delete: logout the connections and delete the file in the gluster volume
> Couple of questions:
> 1. Should Block API have sub API's such as FileCreate, FileList,
> FileResize, File delete and etc then get it used in Block API as they
> mostly deal with files.

IMO, Heketi should not expose any File related API. It should only have
APIs to service request for block devices; how the block devices are
created and modified is an implementation detail.

> 2. How do we create the actual file in the volume, meaning using FUSE
> mount (which may involve an extra process running) or gfapi, again if gfapi
> should we go with c API's, python bindings or go bindings ?
3. Should we get targetcli related (LUN exporting) setup done from heketi
> or do we seek help from gdeploy for this ?

I would prefer to either have it in Heketi or in Kubernetes. If the API in
Heketi promises just the creation of block device, then the rest of the
implementation should be in Kubernetes(the export part). If the API in
Heketi promises create and export both, I would say Heketi should have the
implementation within itself.

> Thoughts?
> Note: nothing is fixed as put in this mail, its all just part of initial
> discussions.
> Cheers,
> --
> Prasanna
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