Add a variable to skip the machine-type validation for TPUs

[agrawalkhushi18]

This change bypasses the node pool's machine-type validation when using aggregate TPU reservations. The existing precondition block fails for TPUs because these reservations do not expose a machine-type field, unlike CPU or GPU reservations, which causes a mismatch error during the terraform plan stage. This fix uses the placement_policy.tpu_topology setting to reliably identify a TPU node pool and conditionally skip this specific validation, unblocking the deployment.

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[gemini-code-assist]

Summary of Changes

Hello @agrawalkhushi18, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an issue where GKE node pools utilizing aggregate TPU reservations would fail during the Terraform plan stage due to a missing machine_type field in TPU reservation definitions. The change introduces a mechanism to detect TPU node pools based on their placement_policy.tpu_topology and then conditionally bypasses the problematic machine-type validation, thereby unblocking the deployment of such configurations.

Highlights

• TPU Detection Variable: A new local variable, is_tpu, has been introduced. This variable is set to true if the placement_policy.tpu_topology is defined, allowing for reliable identification of TPU node pools.
• Conditional Machine-Type Validation: The machine-type validation logic for reservations has been updated to conditionally skip validation for TPU node pools. If is_tpu is true, the reservation_vm_properties list is set to empty, effectively bypassing the validation that previously caused errors for aggregate TPU reservations.

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[gemini-code-assist]

Code Review

The pull request introduces a mechanism to bypass machine-type validation for TPU node pools by checking the placement_policy.tpu_topology setting. This addresses an issue where the existing validation logic fails for TPUs due to the absence of a machine-type field in TPU reservations. The changes involve adding a local variable is_tpu to determine if the node pool is a TPU and conditionally skipping the machine-type validation based on this variable. The code changes look reasonable, and the comments are helpful. I have added a review comment to improve the code.

[shubpal07]

LGTM.
In long term, we may need a robust way to check TPU specific reservations attributes. This may require the corresponding tf data sources to expose the tpu specific properties.

[agrawalkhushi18]

The current PR-test failures appear to be unrelated to the changes introduced in this PR. Merging it after approval.

[agrawalkhushi18]

LGTM. In long term, we may need a robust way to check TPU specific reservations attributes. This may require the corresponding tf data sources to expose the tpu specific properties.

Agreed. This long-term enhancement will be tracked as a child task to expose the necessary TPU reservation properties.