feat: allow v2 volume to attach on the an old and running instance-manager pod

[derekbit]

Which issue(s) this PR fixes:

Issue longhorn/longhorn#9383

What this PR does / why we need it:

Special notes for your reviewer:

Additional documentation or context

[coderabbitai]

Walkthrough

The changes in this pull request primarily enhance the functionality and error handling of the DataStore and volumeMutator components within the Longhorn project. Key modifications include updates to existing methods to improve instance manager retrieval based on image specifications, the introduction of new methods to check instance manager states, and adjustments to the logic for creating default nodes and managing data engines. These changes aim to ensure better management of Longhorn resources and improve the robustness of operations related to instance managers and volumes.

Changes

File	Change Summary
datastore/longhorn.go	- Updated GetInstanceManagerByInstanceRO and GetInstanceManagerByInstance to handle image variable. - Enhanced error messages in GetInstanceManagerByInstanceRO. - Modified CreateDefaultNode to check user settings before creating disks. - Updated GetReadyNodeDiskForBackingImage for additional checks. - Added GetDataEngines method for retrieving enabled data engines. - Refined labeling methods for consistency. - Enhanced validation logic for recurring jobs.
webhook/resources/volume/mutator.go	- Added areAllDefaultInstanceManagersStopped to check if all instance managers are stopped. - Added getActiveInstanceManagerImage to determine the active instance manager image. - Updated Create method to utilize getActiveInstanceManagerImage for image mutation logic.

Assessment against linked issues

Objective	Addressed	Explanation
Support operations on old and running instance-manager pods for restored volumes (Issue #9383)	✅
Allow v2 volume live upgrade without detaching before Longhorn upgrade (Issue #9383)	❌	Changes do not explicitly address live upgrade needs.

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📜 Recent review details

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📥 Commits

Files that changed from the base of the PR and between e7db6e7 and c215fb8.

📒 Files selected for processing (2)

• datastore/longhorn.go (2 hunks)
• webhook/resources/volume/mutator.go (2 hunks)

🧰 Additional context used

🔇 Additional comments (8)

webhook/resources/volume/mutator.go (3)

49-61: Code for areAllDefaultInstanceManagersStopped looks good

The function correctly checks if all default instance managers are stopped by iterating through them and verifying their current state.

---

211-218: Correctly updating the default image for V2 data engine volumes

The logic in the Create method properly updates the defaultImage based on the active instance manager image for V2 data engine volumes. This ensures that the volume uses the correct image during creation.

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63-86: ⚠️ Potential issue

Handle the case when no active instance manager image is found

In the getActiveInstanceManagerImage function, if all default instance managers are stopped and there are no instance managers with a different image, the function returns the defaultInstanceManagerImage. If the intention is to find an active instance manager image different from the default when all defaults are stopped, consider handling the scenario where none is found.

Apply this diff to handle the case:

 for _, im := range ims {
     if im.Spec.Image != defaultInstanceManagerImage {
         return im.Spec.Image, nil
     }
 }
+// If no instance manager with a different image is found, return an error
+return "", errors.New("no active instance manager image found different from the default")

Alternatively, confirm that returning the default image in this case aligns with the expected behavior.

datastore/longhorn.go (5)

3755-3755: Variable 'image' declared to hold the instance image

The variable image is properly declared to store the image specification from the Engine or Replica objects.

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3763-3763: Assigning 'image' from obj.Spec.Image

The image variable correctly retrieves the image specification from both Engine and Replica objects.

Also applies to: 3768-3768

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3776-3776: Fetching default instance manager image

The code accurately retrieves the default instance manager image using GetSettingValueExisted.

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3781-3785: Properly overriding instance manager image for V2 data engine

When the data engine is V2, the code correctly sets instanceManagerImage to the object's image, ensuring the correct instance manager image is used for instance manager selection.

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Line range hint 3787-3798: Ensuring only one instance manager is present per criteria

The code assumes that exactly one instance manager will match the given node, image, type, and data engine. This is acceptable if the system guarantees that only one instance manager exists per these parameters. Please ensure that this assumption holds true in all deployment scenarios.

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[derekbit]

cc @c3y1huang @ChanYiLin @shuo-wu @innobead ready to go.