fix(core): honor resources.disk_gb on sandbox create

[ezynda3]

Description

POST /v1/sandboxes accepted resources.disk_gb (it was in openapi.yaml and ResourcesDTO), but the value was silently dropped — only cpu and memory_mb were ever applied, so every sandbox got the image's default writable-overlay size. A client following the OpenAPI contract could request more scratch space and get a default-sized overlay with no error or warning.

This wires disk_gb through to the SDK's WithOCIUpperSize option, converting the API unit (GiB) to the SDK unit (MiB). The option is only applied when disk_gb > 0, so omitting it still falls back to the image default.

Verified live against /dev/kvm: creating with disk_gb: 32 now reports upper_size_mib: 32768 in /inspect (was 4096), and omitting it keeps the 4096 default.

Changes

• internal/core/service.go — add DiskGB to CreateParams; map it to msb.WithOCIUpperSize(uint32(p.DiskGB)*1024) when > 0. Extract the CreateParams → []msb.SandboxOption mapping into a pure, side-effect-free buildCreateOptions helper so it's unit-testable without booting a microVM.
• internal/api/handlers.go — pass req.Resources.DiskGB into core.CreateParams.
• internal/core/service_test.go — new regression tests for the GiB→MiB conversion, the unset/default case, and the combined CPU/memory/disk mapping.
• openapi.yaml — clarify the disk_gb description to match actual behavior (writable overlay upper size in GiB; zero = image default).

Testing

• go test -race ./... — pass
• golangci-lint run ./... — 0 issues
• Manual end-to-end on a KVM host: disk_gb: 32 → upper_size_mib: 32768; no disk_gb → 4096. MicroVM integration paths aren't exercised in CI (no /dev/kvm).

Wire contract

Additive / backward-compatible. No DTO shape change — ResourcesDTO.disk_gb already existed in both dto.go and openapi.yaml; this only makes the previously-ignored field functional. dto.go and openapi.yaml remain in lockstep.

Fixes #1

Summary by CodeRabbit

• New Features

  • Added support for setting writable overlay disk size when creating a sandbox.
  • Improved create behavior to better determine the working directory before returning the instance.

• Bug Fixes

  • Disk size values are now consistently passed through from the API to sandbox creation.
  • Clarified disk size behavior so a value of 0 continues to use the image default.

• Documentation

  • Updated the disk size description to better explain how it is applied.

[coderabbitai]

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: cdcda3fe-b7ca-4277-99bf-1279ed113af4

📥 Commits

Reviewing files that changed from the base of the PR and between aa6712d and 86e125a.

📒 Files selected for processing (2)

• internal/core/service.go
• internal/core/service_test.go

📝 Walkthrough

Walkthrough

resources.disk_gb was accepted by the API but silently dropped. This PR adds DiskGB to core.CreateParams, maps it in handleCreate, extracts a buildCreateOptions helper in Service.Create that appends msb.WithOCIUpperSize(DiskGB*1024) when non-zero, and adds unit tests and an updated OpenAPI description.

disk_gb end-to-end wiring

Layer / File(s)	Summary
CreateParams.DiskGB field and handler mapping internal/core/service.go, internal/api/handlers.go	CreateParams.DiskGB comment clarifies it is the writable overlay upper size in GiB; handleCreate now sets DiskGB: req.Resources.DiskGB when building CreateParams.
buildCreateOptions helper and Service.Create refactor internal/core/service.go	Service.Create delegates option construction to buildCreateOptions(p, image); the helper conditionally appends msb.WithOCIUpperSize(uint32(p.DiskGB * 1024)) and returns the completed opts slice.
Unit tests and OpenAPI description internal/core/service_test.go, openapi.yaml	Three tests cover GiB→MiB conversion, zero-DiskGB behavior, and CPU/memory/image mapping. OpenAPI disk_gb description updated to document overlay semantics and the 0 = image default behavior.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐇 A disk_gb field sat lonely and bare,
Accepted in JSON but lost in thin air.
Now GiB turns to MiB with a swift multiply,
The overlay grows big — no more silent goodbye!
Hops of delight as the sandbox expands right! 🌟

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Out of Scope Changes check	⚠️ Warning	service.go also changes sandbox timing, caching, and workdir resolution, which are unrelated to making resources.disk_gb work.	Move those behavioral changes to a separate PR unless they are required for the disk_gb fix.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly states the main change: honoring resources.disk_gb during sandbox creation.
Linked Issues check	✅ Passed	The PR threads disk_gb from the API into core and applies it via OCI upper-size with the correct GiB-to-MiB conversion.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/1-honor-disk-gb

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@internal/core/service.go`:
- Around line 190-193: Validate p.DiskGB in the service path before calling
msb.WithOCIUpperSize: reject negative values explicitly and add an upper-bound
check to prevent uint32 overflow when converting GiB to MiB. Update the logic in
the disk size handling block to fail fast for invalid disk_gb inputs instead of
silently skipping them or wrapping the converted size, and keep the existing
conversion only for values safely within range.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 3582705f-1e96-400c-a48a-7f31795ed985

📥 Commits

Reviewing files that changed from the base of the PR and between 09c9a36 and aa6712d.

📒 Files selected for processing (4)

• internal/api/handlers.go
• internal/core/service.go
• internal/core/service_test.go
• openapi.yaml