[pve-devel] checking output of storage plugin API - volume_rollback_is_possible(..., blockers)

[pve-devel] checking output of storage plugin API - volume_rollback_is_possible(..., blockers)

[Andrei Perapiolkin via pve-devel]

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From: Andrei Perapiolkin <andrei.perepiolkin@open-e.com>
To: pve-devel@lists.proxmox.com
Subject: [pve-devel] checking output of storage plugin API - volume_rollback_is_possible(..., blockers)
Date: Wed, 14 May 2025 08:44:11 -0400
Message-ID: <1979bee4-2f4e-4af2-bfb4-3c320f37399e@open-e.com>

Hi,

I'm trying to test specific aspects of the storage plugin API,
and I'm not sure how to verify whether my function 
volume_rollback_is_possible
correctly sets up the blockers list.

I've checked REST API documentation:
https://pve.proxmox.com/pve-docs/api-viewer/index.html#/nodes/{node}/qemu/{vmid}/snapshot/{snapname}/rollback

CLI tool:
qm rollback

But I couldn't find where the list of blockers is returned or printed.

Are there any posts, guides, or documentation on how to test blockers or 
other return values from storage plugins?



Best regards,

Andrei Perepiolkin



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Re: [pve-devel] checking output of storage plugin API - volume_rollback_is_possible(..., blockers)

[Fabian Grünbichler]

> Andrei Perapiolkin via pve-devel <pve-devel@lists.proxmox.com> hat am 14.05.2025 14:44 CEST geschrieben:

> Hi,
> 
> I'm trying to test specific aspects of the storage plugin API,
> and I'm not sure how to verify whether my function 
> volume_rollback_is_possible
> correctly sets up the blockers list.
> 
> I've checked REST API documentation:
> https://pve.proxmox.com/pve-docs/api-viewer/index.html#/nodes/{node}/qemu/{vmid}/snapshot/{snapname}/rollback
> 
> CLI tool:
> qm rollback
> 
> But I couldn't find where the list of blockers is returned or printed.

the $blockers parameter is currently only passed in replication contexts:

https://git.proxmox.com/?p=pve-guest-common.git;a=blob;f=src/PVE/AbstractConfig.pm;h=3d4fcbbf98553b1f4edc8f59307daae1cf1b8a2f;hb=HEAD#l1051

the expected behaviour is to
- fill $blockers with the snapshot names preventing the rollback, if there are any
- to die with an error message if rollback is not possible

the caller can then decide if they want to pass a $blockers reference, and upon
catching the error, inspect it to give a nicer error message.

you can see how the 'zfs' plugin handles it (the only one supporting replication
at the moment):

https://git.proxmox.com/?p=pve-storage.git;a=blob;f=src/PVE/Storage/ZFSPoolPlugin.pm;h=26fb0a4237e5c1013ebfa85ca2cc072c57d2c36f;hb=HEAD#l502

and model your implementation after its behaviour (of course, whether rolling
back is limited to the most recent snapshot like it is with ZFS is up to you
and your storage ;))

> Are there any posts, guides, or documentation on how to test blockers or 
> other return values from storage plugins?

out of interest - is your plugin publicly available?


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Re: [pve-devel] checking output of storage plugin API - volume_rollback_is_possible(..., blockers)

[Andrei Perapiolkin via pve-devel]

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From: Andrei Perapiolkin <andrei.perepiolkin@open-e.com>
To: "Fabian Grünbichler" <f.gruenbichler@proxmox.com>, "Proxmox VE development discussion" <pve-devel@lists.proxmox.com>
Subject: Re: [pve-devel] checking output of storage plugin API - volume_rollback_is_possible(..., blockers)
Date: Thu, 15 May 2025 07:23:29 -0400
Message-ID: <d32e8977-da91-427e-aa15-4937f9894fe3@open-e.com>

Hi Fabian,


Thank you for detailed response.

> out of interest - is your plugin publicly available?

Yes, my plugin is available at https://github.com/open-e/JovianDSS-Proxmox

Regarding blockers usage: 
https://github.com/open-e/JovianDSS-Proxmox/blob/22d0f7f8c4606d470a988fc796b391f50cabd40f/OpenEJovianDSS/Common.pm#L472

Best regards,

Andrei Perepiolkin

On 5/15/25 05:16, Fabian Grünbichler wrote:
>> Andrei Perapiolkin via pve-devel <pve-devel@lists.proxmox.com> hat am 14.05.2025 14:44 CEST geschrieben:
>> Hi,
>>
>> I'm trying to test specific aspects of the storage plugin API,
>> and I'm not sure how to verify whether my function
>> volume_rollback_is_possible
>> correctly sets up the blockers list.
>>
>> I've checked REST API documentation:
>> https://pve.proxmox.com/pve-docs/api-viewer/index.html#/nodes/{node}/qemu/{vmid}/snapshot/{snapname}/rollback
>>
>> CLI tool:
>> qm rollback
>>
>> But I couldn't find where the list of blockers is returned or printed.
> the $blockers parameter is currently only passed in replication contexts:
>
> https://git.proxmox.com/?p=pve-guest-common.git;a=blob;f=src/PVE/AbstractConfig.pm;h=3d4fcbbf98553b1f4edc8f59307daae1cf1b8a2f;hb=HEAD#l1051
>
> the expected behaviour is to
> - fill $blockers with the snapshot names preventing the rollback, if there are any
> - to die with an error message if rollback is not possible
>
> the caller can then decide if they want to pass a $blockers reference, and upon
> catching the error, inspect it to give a nicer error message.
>
> you can see how the 'zfs' plugin handles it (the only one supporting replication
> at the moment):
>
> https://git.proxmox.com/?p=pve-storage.git;a=blob;f=src/PVE/Storage/ZFSPoolPlugin.pm;h=26fb0a4237e5c1013ebfa85ca2cc072c57d2c36f;hb=HEAD#l502
>
> and model your implementation after its behaviour (of course, whether rolling
> back is limited to the most recent snapshot like it is with ZFS is up to you
> and your storage ;))
>
>> Are there any posts, guides, or documentation on how to test blockers or
>> other return values from storage plugins?
> out of interest - is your plugin publicly available?
>


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Re: [pve-devel] checking output of storage plugin API - volume_rollback_is_possible(..., blockers)

[Fabian Grünbichler]

> Andrei Perapiolkin <andrei.perepiolkin@open-e.com> hat am 15.05.2025 13:23 CEST geschrieben:
> 
>  
> Hi Fabian,
> 
> 
> Thank you for detailed response.
> 
> > out of interest - is your plugin publicly available?
> 
> Yes, my plugin is available at https://github.com/open-e/JovianDSS-Proxmox
> 
> Regarding blockers usage: 
> https://github.com/open-e/JovianDSS-Proxmox/blob/22d0f7f8c4606d470a988fc796b391f50cabd40f/OpenEJovianDSS/Common.pm#L472

depending on what the return value/$obj there is, that looks fine to me!

you could optimize the $blocker_found variable away, and just check
whether $blockers has any elements, but that's just making the code
a bit shorter :)


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