🐛(metrics) Initialize metrics for autoscaler errors, scale events, and pod evictions

[thiha-min-thant]

• Set initial count to zero for various autoscaler error types (e.g., CloudProviderError, ApiCallError)
• Define failed scale-up reasons and initialize metrics (e.g., CloudProviderError, APIError)
• Initialize pod eviction result counters for success and failure cases
• Initialize skipped scale events for CPU and memory resource limits in both scale-up and scale-down directions

What type of PR is this?

/kind bug

What this PR does / why we need it:

This PR initializes the failedScaleUpCount and other key metrics at startup, setting their values to zero so they appear in Prometheus even if no events have occurred. By pre-defining these metrics, we ensure comprehensive monitoring and avoid gaps in visibility, particularly for scale-up and scale-down events, error types, and pod evictions.

Which issue(s) this PR fixes:

Fixes #7448

Special notes for your reviewer:

Certain node metrics have not been initialized in this PR because they require runtime information. These metrics are tied to dynamic node states and cannot be set at startup.

Metrics Log Reference:
metrics.txt

Metrics requiring runtime data include:

node_group_min_count
node_group_max_count
node_group_target_count
node_group_healthiness
scaled_up_gpu_nodes_total
failed_gpu_scale_ups_total
scaled_down_gpu_nodes_total
unremovable_nodes_count ?
created_node_groups_total
deleted_node_groups_total
node_taints_count

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: thiha-min-thant
Once this PR has been reviewed and has the lgtm label, please assign bigdarkclown for approval. For more information see the Kubernetes Code Review Process.

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[thiha-min-thant]

Hi @JoelSpeed @elmiko , could you please review this PR? Thanks!

[elmiko]

thanks for picking this up @thiha-min-thant !

[thiha-min-thant]

Hi @JoelSpeed and @elmiko,

I've made updates to both the code and the PR description to clarify the initialization of metrics and added a metrics log file as a reference.

Thanks for your feedback, and please take a look at these updates when you have a chance!

[JoelSpeed]

Do you know if the following also need initialisation?

pending_node_deletions
errors_total
failed_scale_ups_total
scaled_down_nodes_total
skipped_scale_events_count

[thiha-min-thant]

Do you know if the following also need initialisation?

pending_node_deletions
errors_total
failed_scale_ups_total
scaled_down_nodes_total
skipped_scale_events_count

pending_node_deletions is already initialized and I already add initialization for the rest.

[JoelSpeed]

/lgtm

[elmiko]

this is great, will make it easier if we need to update in the future.

/lgtm

[thiha-min-thant]

Hi @JoelSpeed and @elmiko,

If the code looks good to both of you, could we proceed with the merge? We’re just one /approve label away. Thanks for your review!

[JoelSpeed]

/assign @BigDarkClown

@BigDarkClown the bot of assignment chose you for this one, could we get this approved?

[elmiko]

@thiha-min-thant we need one of the maintainers for this area of the code to approve it. that's the only thing we are waiting on currently.