[Bug 2121812] [NEW] [SRU] cinder-netapp driver fails to start when a node is down

[Launchpad Bug Tracker]

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We're trying to use cinder-netapp, and the driver fails to start with the following error.
https://pastebin.ubuntu.com/p/dwMdrVwdtf/

After enabling debugging, I noticed that one node doesn't report its model.
Checking on netapp side, the node is down due to a hardware issue, and another one is taking over the current node.

If i add or ''  to get_cluster_nodes_info. it works fine.

In this current setup, if any node goes down and the driver restarts,
Cinder won't be able to recover.


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[SRU]

[Impact]
cinder-volume service fails to start when cinder-netapp driver is used with some netapp nodes in maintenance state.

The service during driver initialization queries the netapp server for all the nodes information. Typically the node
name, model and certain other attributes are expected. However in case if the node is in maintenance mode, the
model information is missing.
cinder-volume service does not handle properly in case the model value is None and so the service goes to failed state.

The fix checks if the model value is None and assigns empty string as default value. In addition, a warning message is
logged for missing model values.

[Test Case]
To test the fix, netapp storage nodes are required.
However the effect of the fix can be easily tested using unit testing by simple changes.

In the file tests/unit/volume/drivers/netapp/dataontap/fakes.py
Change the model value in dict NO_MODEL_NODE to None instead of ''
Run `tox -e py3 -- cinder.tests.unit.volume.drivers.netapp.dataontap.client.test_client_cmode_rest.NetAppRestCmodeClientTestCase`

All the test cases failed in driver initialization with following error:
TypeError: argument of type 'NoneType' is not iterable

[Regression Potential]
In order to mitigate any regression potential, the fix has been tested with real hardware for jammy caracal
Also the default logic is not changed when model is provided by netapp server.

[Discussion]
n/a

** Affects: cinder
     Importance: Undecided
     Assignee: Hemanth Nakkina (hemanth-n)
         Status: In Progress

** Affects: cloud-archive
     Importance: Undecided
         Status: New

** Affects: cloud-archive/caracal
     Importance: Undecided
         Status: New

** Affects: cloud-archive/epoxy
     Importance: Undecided
         Status: New

** Affects: cinder (Ubuntu)
     Importance: Undecided
         Status: New

** Affects: cinder (Ubuntu Noble)
     Importance: Undecided
         Status: New

** Affects: cinder (Ubuntu Plucky)
     Importance: Undecided
         Status: New

** Affects: cinder (Ubuntu Questing)
     Importance: Undecided
         Status: New


** Tags: patch
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[SRU] cinder-netapp driver fails to start when a node is down
https://bugs.launchpad.net/bugs/2121812
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