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On 3/1/23 12:19 PM, Ghanshyam Mann wrote:
>   ---- On Wed, 01 Mar 2023 09:02:59 -0800  Brian Rosmaita  wrote ---
>   > On 2/28/23 9:02 PM, Ghanshyam Mann wrote:
>   > [snip]
>   >
>   > > I think removing from client is good way to stop exposing this old/not-recommended way to users
>   > > but API is separate things and removing the API request parameter 'multiattach' from it can break
>   > > the existing users using it this way. Tempest test is one good example of such users use case. To maintain
>   > > the backward compatibility/interoperability it should be removed by bumping the microversion so that
>   > > it continue working for older microversions. This way we will not break the existing users and will
>   > > provide the new way for users to start using.
>   >
>   > It's not just that this is not recommended, it can lead to data loss.
>   > We should only allow multiattach for volume types that actually support
>   > it.  So I see this as a case of "I broke your script now, but you'll
>   > thank me later".
>   >
>   > We could microversion this, but then an end user has to go out of the
>   > way and add the correct mv to their request to get the correct behavior.
>   >   Someone using the default mv + multiattach=true will unknowingly put
>   > themselves into a data loss situation.  I think it's better to break
>   > that person's API request.
> 
> Ok, if multiattach=True in the request is always an unsuccessful case (or unknown successful sometimes)
> then I think changing it without microversion bump makes sense. But if we know there is any success case
> for xyz configuration/backend then I feel we should not break such success use case.

Thanks, Ghanshyam.  An end user is setting themselves up for data loss 
if they rely on the request parameter rather than on using a volume type 
that explicitly supports multiattach.  They could get lucky and not lose 
any data, but that's not really a success, so I think the best thing to 
do here is make this breaking change without a microversion.

> I was just thinking from the Tempest test perspective which was passing but as you corrected me in IRC,
> the test does not check the data things so we do not completely test it in Tempest.

It's good that Tempest is there to keep us honest!  I think what we can 
do to help out people whose scripts break is to return a specific error 
message explaining that the 'multiattach' element is not allowed in a 
volume-create request and instead the user should select a 
multiattach-capable volume type.

> 
> -gmann
> 
>   >
>   >
>   > cheers,
>   > brian
>   >
>   >
>   >