[ARO-25489] Reduce the memory usage of ResourceSKUs querying

[hawkowl]

Which issue this PR addresses:

Part of [ARO-25489]

What this PR does / why we need it:

I have an inkling that this list in larger regions is consuming a lot of memory. So, let's consume less :)

Test plan for issue:

Unit tests provided, E2E

Is there any documentation that needs to be updated for this PR?

N/A

How do you know this will function as expected in production?

E2E, hopefully

[Copilot]

Pull request overview

This PR reduces memory usage when querying Azure Compute Resource SKUs by switching from building full in-memory SKU lists to streaming/iterating SKUs and only retaining the subset needed by callers (or just names for admin listing).

Changes:

• Changed ResourceSKUsClient.List to return an iterator (iter.Seq2) instead of []*ResourceSKU, enabling streaming pagination.
• Added computeskus.SelectVMSkusInCurrentRegion and computeskus.ListUnrestrictedVMSkusInCurrentRegion to avoid loading all SKUs into memory.
• Updated frontend/admin/cluster flows and tests to use the new iterator-based SKU querying.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
pkg/util/azureclient/azuresdk/armcompute/resourceskus_addons.go	Reworks SKU listing to stream results via iter.Seq2 instead of returning a full slice.
pkg/util/mocks/azureclient/azuresdk/armcompute/armcompute.go	Updates generated mock to match the iterator-based List signature.
pkg/util/computeskus/computeskus.go	Introduces streaming-based SKU selection/listing helpers and updates error handling accordingly.
pkg/util/computeskus/computeskus_test.go	Replaces old FilterVMSizes test with new unit tests for streaming-based helpers.
pkg/frontend/sku_validation.go	Uses SelectVMSkusInCurrentRegion to fetch only the SKUs referenced by the cluster doc.
pkg/frontend/sku_test.go	Updates mocks and expected errors for iterator-based SKU listing.
pkg/frontend/adminactions/azureactions.go	Changes admin VM SKU listing to return []string and adds VMGetSKUs for targeted queries.
pkg/util/mocks/adminactions/azureactions.go	Updates generated adminactions mocks for VMSizeList type change and new VMGetSKUs.
pkg/frontend/admin_openshiftcluster_vmsizelist.go	Removes local filtering logic; now sorts and returns the already-filtered SKU name list.
pkg/frontend/admin_openshiftcluster_vmsizelist_test.go	Updates expectations to reflect []string return type and stable sorting.
pkg/frontend/admin_openshiftcluster_vmresize_pre_validation.go	Switches pre-resize validation to query only the desired SKU via VMGetSKUs.
pkg/frontend/admin_openshiftcluster_vmresize_pre_validation_test.go	Updates mocks to use VMGetSKUs and map-based SKU lookup.
pkg/cluster/validate.go	Switches zone validation to only fetch SKUs needed for master/worker sizing.
pkg/cluster/validate_test.go	Updates SKU client mocks to return iterators rather than slices.
pkg/cluster/loadbalancerinternal.go	Changes load balancer zonal migration path to fetch only the needed SKU(s).
pkg/cluster/loadbalancerinternal_test.go	Updates SKU client mocks to return iterators rather than slices.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[hawkowl]

/azp run ci

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[tsatam]

We'd want to validate all worker profiles here, correct? Not just the first entry in the array?

[hawkowl]

This is the bootstrap version, which only supports 1 entry -- the actual sku check below it also only does the first entry

[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 11 comments.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

This map literal uses key type *armcompute.ResourceSKU but the keys are written as struct literals ({ ... }) without taking an address. This will not compile; the keys need to be &armcompute.ResourceSKU{...} (and the same applies to the other maps.All(map[*armcompute.ResourceSKU]error{ ... }) blocks in this file).

[Copilot]

Same issue here: the maps.All(map[*armcompute.ResourceSKU]error{ ... }) literal is keyed by *armcompute.ResourceSKU but the keys are not address-of expressions. This won’t compile until the keys are changed to &armcompute.ResourceSKU{...}.

[Copilot]

Same compile issue: keys in this map[*armcompute.ResourceSKU]error literal need to be pointers (&armcompute.ResourceSKU{...}), not struct literals.

[Copilot]

Same compile issue: keys in this map[*armcompute.ResourceSKU]error literal must be pointer values (use &armcompute.ResourceSKU{...}), otherwise the test won’t compile.

[Copilot]

Same compile issue: this map[*armcompute.ResourceSKU]error literal uses non-pointer struct literals as keys. Change the keys to &armcompute.ResourceSKU{...} so the test compiles.

[Copilot]

Same compile issue: this map[*armcompute.ResourceSKU]error uses struct literals as keys instead of &armcompute.ResourceSKU{...} pointers.

[Copilot]

sku.Restrictions is a slice of pointers in the Azure SDK; individual entries can be nil. This code dereferences restriction.RestrictionInfo without checking restriction != nil, which can panic if a nil restriction is returned. Add a nil check for restriction before accessing its fields.

[Copilot]

Potential nil dereferences: sku can be nil (the iterator’s contract allows yielding nil), and the SDK fields ResourceType / Name are pointers. Dereferencing *sku.ResourceType and *sku.Name without nil checks can panic on unexpected API responses. Add guards for sku == nil, sku.ResourceType == nil, and sku.Name == nil before dereferencing.