added nodeVolumeAttachLimit

[mganter]

How to categorize this PR?

/area robustness
/area storage
/kind enhancement
/priority normal
/platform openstack

What this PR does / why we need it:
The introduced flag tells the CSI-Driver, that there is a upper limit for mounted volumes on a node.

Release note:

Added possibility to set nodeVolumeAttachLimit within the cloud profile.

[CLAassistant]

All committers have signed the CLA.

[gardener-robot]

@mganter Thank you for your contribution.

[gardener-robot-ci-3]

Thank you @mganter for your contribution. Before I can start building your PR, a member of the organization must set the required label(s) {'reviewed/ok-to-test'}. Once started, you can check the build status in the PR checks section below.

[dkistner]

Hi @mganter.
Thanks you very much for the PR.
I will have a look soon.

[dkistner]

Thanks @mganter
I had a brief look. Can you elaborate a little bit on the reasons why the amount of volumes per node need to be limited?
Should that not rather be configured for each Shoot cluster individually instead of globally via the CloudProfile?

[mganter]

The limit exists inside of OpenStack. With this option you can tell the scheduler, that he shall not schedule more cinder volumes to a specific node than the specified amount.

If the scheduler does't know it, he will schedule pods to nodes where they can't be satisfied in terms of volumes. So pods will remain in container creation state.

[dkistner]

Thanks for explanation. I played a little bit around with it and configured a limit of just two disks per node.
If I try to schedule more pods with disks to a node the scheduler tells:

I1019 19:50:13.426597       1 factory.go:445] "Unable to schedule pod; no fit; waiting" pod="default/some-persistence-2" err="0/1 nodes are available: 1 node(s) exceed max volume count."

Also there is an event which indicate the same:

2m34s       Warning   FailedScheduling          pod/some-persistence-2                                            0/1 nodes are available: 1 node(s) exceed max volume count.

The pr looks overall very nice. The tests for the valuesprovider/controlplane controller needs to be adapted. They fail because the new property nodeVolumeAttachLimit is missing here: https://github.com/gardener/gardener-extension-provider-openstack/blob/master/pkg/controller/controlplane/valuesprovider_test.go#L247-L262

We should also mention in the operator docs that this feature will only be available when using CSI.

[mganter]

Added docs. Updated test.

[rfranzke]

/reviewed ok-to-test

[rfranzke]

@mganter can you check the failing CI? probably you need to run make generate
/status author-action

[gardener-robot]

@mganter The pull request was assigned to you under author-action. Please unassign yourself when you are done. Thank you.

[mganter]

@mganter can you check the failing CI? probably you need to run make generate
/status author-action

make generate results in no change of code. Removing controller-registration.yaml results in recreating it exactly with no diff. I rebased it to the latest rev.

Some system information:
I'm running Manjaro Kernel: Linux 5.8.11-1-MANJARO
ldd (GNU libc) 2.32

Do you know if there are any issues with that?

[rfranzke]

Now there is a conflict.

Do you know if there are any issues with that?

Hm, good question, can you run make install-requirements and try again?

[mganter]

The conflict is resolved now. (Didn't have the changes from 1 hour ago)
And its re-generated.
I also re-run make install-requirements.

[rfranzke]

Thanks @mganter!

[mganter]

Thank you very much @rfranzke @dkistner