Introduce accelerators.json as Single Source of Truth for GCE machine types

[SwarnaBharathiMantena]

The machine_type to accelerator_type and count mapping is placed in a single file for ease of maintenance and have a single source of truth.

This file will also be used in updating go logic and avoids creation of a new map for go code alone.

Solution

Go Configuration Engine (pkg/config/expand.go):

• Uses go:embed to securely embed accelerators.json directly into the Go binary.
• Dynamically injects the JSON string as an accelerator_configs variable into any module that declares it in its inputs (in expandModule).

Terraform Modules (modules/internal/gpu-definition and tpu-definition):

• Main Configuration: Replaced jsondecode(file("${path.module}/...")) with jsondecode(var.accelerator_configs).
• Variables: Added the accelerator_configs string variable type to accept the injected JSON from Go.

[gemini-code-assist]

Summary of Changes

Hello, 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 centralizes the management of GCE machine type mappings for GPUs and TPUs. By moving these definitions into a shared JSON file, the configuration becomes easier to maintain and can be reused across different parts of the codebase, including Go logic, thereby reducing duplication and potential for configuration drift.

Highlights

• Centralized Configuration: Introduced a new pkg/config/accelerators.json file to serve as the single source of truth for GPU and TPU machine type mappings.
• Terraform Refactoring: Updated gpu-definition and tpu-definition Terraform modules to dynamically load accelerator configurations from the new JSON file instead of using hardcoded local maps.

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[gemini-code-assist]

Code Review

This pull request centralizes GPU and TPU machine type definitions by migrating hardcoded HCL maps from the gpu-definition and tpu-definition modules into a shared JSON configuration file at pkg/config/accelerators.json. A critical issue was identified where several g4-standard machine types (6, 12, and 24) were omitted during the migration, which would result in a breaking change for users of those machine types.

[SwarnaBharathiMantena]

/gcbrun