feat(CSI-252): implement kubelet PVC stats

[sergeyberezansky]

TL;DR

Implemented NodeGetVolumeStats functionality and added new node service capabilities.

What changed?

• Implemented NodeGetVolumeStats method in the NodeServer struct.
• Added getVolumeStats helper function to fetch filesystem statistics.
• Updated NewNodeServer to include new node service capabilities:
  • SINGLE_NODE_MULTI_WRITER
  • GET_VOLUME_STATS
  • VOLUME_CONDITION

How to test?

1. Mount a Weka volume to a node.
2. Call the NodeGetVolumeStats method with the volume ID and path.
3. Verify that the method returns correct capacity, used, and available bytes.
4. Test error cases by providing invalid volume IDs or non-existent paths.
5. Verify that the new node service capabilities are reported correctly.

Why make this change?

This change enhances the CSI driver's functionality by implementing volume statistics retrieval. It allows Kubernetes to query volume usage information, which is crucial for monitoring and managing storage resources. The added node service capabilities also improve the driver's feature set, making it more compliant with CSI specifications and providing better support for various storage operations.

Following this improvement, the following metrics become available for Weka CSI volumes:

kubelet_volume_stats_capacity_bytes
kubelet_volume_stats_available_bytes
kubelet_volume_stats_used_bytes
kubelet_volume_stats_inodes
kubelet_volume_stats_inodes_free
kubelet_volume_stats_inodes_used

---

[sergeyberezansky]

• chore(deps): update sidecar versions #326
• docs(CSI-254): update official docs link in Helm templates and README #323
• feat(CSI-252): implement kubelet PVC stats #322 👈
• refactor(CSI-250): do not maintain redundant active mounts from node server after publishing volume #320
• feat(CSI-247): implement InterfaceGroup.GetRandomIpAddress() #319
• feat(CSI-249): optimize NFS mounter to use multiple targets #318
• fix(CSI-241): fix unmountWithOptions to use map key rather than options.String() #317
• feat(CSI-245): allow specifying client group for NFS #316
• chore(deps): update packages to latest versions and Go to 1.22.5 #314
• chore(deps): combine chmod with ADD in Dockerfile #313
• feat(CSI-239): moveToTrash does not return error to upper layers #312
• fix(CSI-243): service accounts for CSI plugin assume ImagePullSecret and cause error messages. #311
• feat(CSI-244): match subnets if existing in client rule #315
• fix(CSI-241): conflict in metrics between node and controller #325
• feat(CSI-213): support NFS transport #299
• fix(CSI-241): disregard sync_on_close in mountmap per FS #310
• feat(CSI-253): support custom CA certificate in API secret #324
• dev

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"Request reviewers once CI passes" took an action on this PR • (09/09/24)

1 reviewer was added to this PR based on Sergey Berezansky's automation.

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Merge activity

• Sep 12, 6:10 AM EDT: @sergeyberezansky started a stack merge that includes this pull request via Graphite.
• Sep 12, 7:43 AM EDT: Graphite couldn't merge this pull request because a downstack PR feat(CSI-245): allow specifying client group for NFS #316 failed to merge.
• Sep 12, 8:43 AM EDT: @sergeyberezansky started a stack merge that includes this pull request via Graphite.
• Sep 12, 8:45 AM EDT: The Graphite merge of this pull request was cancelled.