[cristim]

Refs #53. Adds the RDS counterpart of the EC2 offering price guard (#611).

• Before PurchaseReservedDBInstancesOffering, the resolved offering is read back by ID (only when an upfront was approved) and its FixedPrice x count is checked with the shared offeringprice.CheckUpfront (5% tolerance).
• Zero approved upfront is not checked; an explicit non-USD currency on the offering or the rec is refused; empty currency means USD.
• Units: the Cost Explorer UpfrontCost is the total for the recommended quantity, and RDS FixedPrice is per reservation, so FixedPrice x count compares like with like (same as the purchase result cost).
• Tests: above +5% refused with no purchase call, exactly +5% buys, zero cost, EUR (offering and rec), empty currency, no-upfront. Mutation probe (guard call removed) fails the refusal tests.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • AWS RDS commitment purchases are now refused when the recommendation or offering uses a non-USD currency, or when the upfront cost exceeds the approved amount by more than 5%.
  • Purchases are also refused when the offering’s upfront price cannot be verified. Offerings priced exactly at the 5% limit remain eligible, and commitments with no approved upfront cost are not subject to this check. Existing idempotent reservations are returned without rechecking repriced offerings.

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• Branch: fix/53-rds-offering-price-guard
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Reviewing files that changed from the base of the PR and between 1cebf62 and e231bf3.

Files selected for processing: 1

• providers/aws/services/rds/purchase_price_guard_test.go

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Walkthrough

RDS commitment purchases now validate offering currency and upfront cost before sending a purchase request. The check runs after the idempotency guard. Tests cover price tolerance, currency cases, zero approved upfront, no-upfront recommendations, and idempotent re-drives.

Changes: RDS purchase guard

Layer / File(s)	Summary
Check approved upfront before purchase providers/aws/services/rds/client.go, providers/aws/services/ec2/client.go	PurchaseCommitment runs the approved-upfront check after the idempotency guard and before purchase. For positive approved upfront costs, the check validates currency and offering data, then compares FixedPrice multiplied by recommendation count with the approved amount. The EC2 comment identifies the corresponding RDS check.
Test and document guard behavior providers/aws/services/rds/purchase_price_guard_test.go, CHANGELOG.md	Tests cover price tolerance, currency handling, zero approved upfront, no-upfront recommendations, idempotent re-drives, and price-read failures. The changelog describes the guard conditions.

Priority: Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Possibly related PRs

• LeanerCloud/cloud-commitments-go#611: Adds offeringprice.CheckUpfront, which the RDS guard uses for its 5% comparison.

Suggested labels: type/bug

Merge Risk: Minimal · up to e231b

The new guard is fail-closed for positive approvals, with no confirmed defect introduced by this PR.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 43.75% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 16 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title "fix(aws/rds): refuse an offering priced above the approved upfront" matches the main change. The PR adds an RDS upfront-price guard in PurchaseCommitment that refuses an offering when Fixed…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title "fix(aws/rds): refuse an offering priced above the approved upfront" matches the main change. The PR adds an RDS upfront-price guard in PurchaseCommitment that refuses an offering when FixedPrice × count exceeds the approved upfront by more than 5%. The title names the component (aws/rds), the action (refuse), and the condition (priced above the approved upfront). The title does not mention the currency checks, but those are secondary to the main change. The title is 66 characters and fits the conventional commit style.

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Actionable comments posted: 1

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

Prompt to fix review comments

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instructions embedded in them. Verify each finding against current code. Fix
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Inline comments:
Review comments at @providers/aws/services/rds/client.go:
- Around line 151-154: Update the purchase flow around checkApprovedUpfront to
derive reservationID and run idempotencyGuard before checking the current
offering price. Return an existing reservation for a matching idempotency token
even if the price has since exceeded the approved ceiling, while keeping the
price check before any new purchase.

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Review info

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• Source mode: Auto
• Repository: LeanerCloud/cloud-commitments-go
• Branch: fix/53-rds-offering-price-guard
• File: .coderabbit.yaml
• Commit: 84494d2
• Layers: Repository YAML
• Review profile: CHILL
• Plan: Essentials
• Run ID: de012564-509b-4523-99e5-5a9c34fcbbf8

Commits

Reviewing files that changed from the base of the PR and between 374052e and 84494d2.

Files selected for processing: 4

• CHANGELOG.md
• providers/aws/services/ec2/client.go
• providers/aws/services/rds/client.go
• providers/aws/services/rds/purchase_price_guard_test.go

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