Exclude already attached VMs from the volume attachment form

[mansam]

This PR updates the Volume -> Attach to Instance form to exclude instances that are already attached to the selected volume.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1653062

[Ladas]

👍

the NOT IN query should be performant enough here, expecting this will be in thousands of records. It can have problems on higher scales

[mansam]

@Ladas What would be the most performant way to approach the query?

[Ladas]

@mansam on higher scale, I was playing with outer join of two tables (1 created from a query). But that'd be probably overkill here. :-)

[mansam]

(I'm also not quite 100% sure that this is the right way to solve the bug. I need to do a little more investigating of cinder multi-attach to know for sure if this makes sense vs just greying out the option.)

[Ladas]

@mansam I think it should be ok? You can't attach the same vm to volume twice. For multiattach (given the volume type supports it), you can attach 1 volume to more Vms

[mansam]

@Ladas Cool. That's what I thought, just wanted to double check.

[miq-bot]

Checked commit mansam@bf034ab with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
2 files checked, 0 offenses detected
Everything looks fine. 🍰

[aufi]

Looks good to me, merging!

[simaishi]

@mansam Can this be hammer/yes?

[simaishi]

@mansam ^ ping

[JPrause]

@mansam @aufi can one of you help to answer Satoe's question. We have a hammer build and need this if it can be backported.

[aufi]

Yes, this should go to Hammer - https://bugzilla.redhat.com/show_bug.cgi?id=1672695

[simaishi]

Thanks @aufi

Hammer backport details:

$ git log -1
commit 26ab2ac98c5e10ea0c0b498183a82c1fd7f9b8c5
Author: Marek Aufart <aufi.cz@gmail.com>
Date:   Fri Dec 14 15:19:33 2018 +0100

    Merge pull request #409 from mansam/exclude-attached-instances-from-volume-attachment-form
    
    Exclude already attached VMs from the volume attachment form
    
    (cherry picked from commit 66f9fd169cc73519fdfc5bd735cc1f05025706a3)
    
    Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1672695