feat(ladder): expose scoped EC2 commitment rates

[cristim]

The allocator needs new-purchase commitment rates, but the AWS ladder doesn't expose its existing Cost Explorer rate reader. This adds an optional typed capability and wires the regional EC2 Instance SP reader through a factory that accepts resolved AWS credentials and transport configuration.

Missing recommendations return an empty rate map so allocation stays on Hold, while malformed responses and provider errors remain errors. Compute SP and Convertible RI rates stay absent. There's no implicit Compute blend or EC2 proxy, and execution remains disabled.

The AWS module now selects the already published shared allocation contract. Standalone AWS race tests and build passed, along with pinned lint and normal commit hooks. Constructed CE-shaped responses through a loopback server exercise the real SDK encoder/decoder, account and region filtering, pagination, allocation, stored tranche rates and repeat-run Holds. These are fixture-based results, not live AWS acceptance.

A separate external consumer checks the optional interface with coherent shared/provider modules. Fresh committed-code review and replacement-free immutable-module verification are in progress, and their exact-head evidence will be recorded here before merge.

Refs #349. Residual-baseline integration, existing-exposure normalization, platform stored-rate/netting migration and executor wiring remain prerequisites tracked by #282 and the platform ladder work.

Summary by CodeRabbit

• New Features
  • AWS commitment allocation can now use available EC2 Instance Savings Plan commitment rates, matched to the configured account, region, term, and payment option.
  • When rate data is unavailable, the allocation is held rather than proceeding with an unsupported rate.

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Reviewing files that changed from the base of the PR and between 5b25448 and 8612582.

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• providers/aws/go.sum is excluded by !**/*.sum

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• providers/aws/go.mod

📝 Walkthrough

Adds an optional commitment-rate capability and implements it in the AWS ladder. The ladder queries for EC2 Instance Savings Plan rates, and tests cover source requests, SDK responses, and allocation behavior.

Changes: AWS commitment rate retrieval

Layer / File(s)	Summary
Capability and AWS ladder wiring pkg/ladder/capability.go, providers/aws/ladder/factory.go, providers/aws/ladder/ladder.go, providers/aws/go.mod	Adds the optional CommitmentRateCapability interface and wires the AWS ladder with a commitment-rate source. Adds NewFromConfig to accept resolved AWS configuration and ladder settings.
AWS commitment-rate lookup providers/aws/ladder/commitment_rates.go	Adds AWSLadder.GetCommitmentRates. It validates inputs, queries for the EC2 Instance Savings Plan rate, returns an empty map when no rate exists, and wraps other errors.
Rate retrieval and allocation tests providers/aws/ladder/commitment_rates_test.go, providers/aws/ladder/commitment_rates_sdk_test.go	Adds tests for configuration, request parameters, paginated SDK responses, account and region filtering, allocation results, missing rates, and malformed cost data.

Priority: ⬇️ Low

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

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant Caller
  participant AWSLadder
  participant spCommitmentRateSource
  participant CostExplorer
  Caller->>AWSLadder: GetCommitmentRates(scope, term, payment)
  AWSLadder->>spCommitmentRateSource: Query using account, region, term, payment, and lookback
  spCommitmentRateSource->>CostExplorer: Request EC2 Instance Savings Plan rate
  CostExplorer-->>spCommitmentRateSource: Rate data
  spCommitmentRateSource-->>AWSLadder: Rate or error
  AWSLadder-->>Caller: Per-layer rate map or error

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Merge Risk: 🔵 Low · up to 5b254

Standalone consumers cannot use the new interface with the AWS module’s declared dependency alone. Update the dependency before release; consumers can work around it by selecting a newer pkg version.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 21.43% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 14 functions across 6 files. (1 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
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.
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: exposing scoped EC2 commitment rates through the ladder.

Full details: Docstring Coverage

Explanation

Docstring coverage is 21.43% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 14 functions across 6 files. (1 skipped: 1 unsupported.)

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[cristim]

@coderabbitai review

[cristim]

Local implementation review covers head 5b25448 and tree 26e278c1d9b20f6a49ea526f3df0e9a5ccf5e7d3 against main 29adce1.

The independent gpt-6.1-sol medium reviewer completed two clean final passes after resolving two findings: pagination fixtures now have different page rates, and standalone AWS tests select the published shared allocation contract instead of depending on workspace overrides. It traced factory delegation and source wiring, scope guards, typed parameters, error identity, missing-data Holds and EC2-only output, with no duplicated CE calculation or Compute proxy.

The module correction was verified against the published Go module: v0.0.0-20261014214001-29adce1c3883. Standalone tests failed before that correction with missing allocation/tranche symbols. Afterward, the full AWS race suite passed with GOWORK=off, as did the standalone build. The final fixture-only change passed the focused standalone ladder race suite in 1.444s. CI-pinned lint 2.10.1 built with Go 1.26.9 passed for AWS and the shared ladder package, and all normal commit hooks passed.

Constructed local CE responses exercise the real SDK encoder/decoder and public factory, including two-page contribution, foreign account and region filtering, missing and malformed data, OD-to-commitment allocation, stored tranche rates and repeat-run Holds. Tracked fixtures use explicit account placeholders; the separate external consumer retains the documented twelve-digit example. These results don't establish live AWS billing semantics or acceptance.

Fresh cold review, scratch mutation proof and replacement-free published-module consumer verification are running independently on this exact committed head. Required CI remains a merge gate. The required pre-commit workflow 38698157103 has completed successfully; build/test workflow 38698157088 is still running under its own watcher.

[coderabbitai]

Actionable comments posted: 1

---

• 🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @providers/aws/go.mod:
- Line 6: Update the pkg dependency version in the AWS module’s go.mod to a
release that includes CommitmentRateCapability, so standalone consumers can
compile against the advertised interface without adding another dependency.

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⛔ Files ignored due to path filters: 1

• providers/aws/go.sum is excluded by !**/*.sum

📒 Files selected for processing: 7

• pkg/ladder/capability.go
• providers/aws/go.mod
• providers/aws/ladder/commitment_rates.go
• providers/aws/ladder/commitment_rates_sdk_test.go
• providers/aws/ladder/commitment_rates_test.go
• providers/aws/ladder/factory.go
• providers/aws/ladder/ladder.go

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[cristim]

Independent adversarial review: no actionable findings after two retained passes by gpt-6.1-sol (medium), against head 5b254484d5e43e8446fc8278504b71a5857e504a, tree 26e278c1d9b20f6a49ea526f3df0e9a5ccf5e7d3, base 29adce1c3883bfb71a926451c323eafea601e87f.

Pass 1 attacked correctness, account isolation, failure semantics, and source-of-truth alignment. Pass 2 rechecked the complete diff for completeness, security, races/edge cases, reuse, unnecessary machinery, compatibility, and scope. The PR body was treated as a claim. No author files were edited.

• pkg/ladder/capability.go:9: the new interface is optional; the existing required provider interface is unchanged.
• providers/aws/ladder/commitment_rates.go:20-46: scope/term/payment validation precedes the source; only regional EC2 Instance recommendations are requested; typed absence becomes a non-nil empty map; other failures propagate; Compute is absent. providers/aws/ladder/commitments.go:42-50 enforces provider/account equality.
• providers/aws/ladder/factory.go:63-98: both constructors share the production SDK wiring; configuration is copied before changing the region; the existing recommendations client supplies rates. No purchase, executor, or arming path was changed. Removing the extra constructor would remove the resolved-config public consumer path exercised below.
• The unchanged lower client is the source of calculation: providers/aws/recommendations/sp_commitment_rate.go:61-114 aggregates all pages, :117-140 maps API selection, :144-153 filters account/region, and :157-185 strictly parses the existing cost/utilization formula. No formula was added or copied into the adapter.
• Compared those selections and detail fields with the installed AWS Cost Explorer SDK v1.61.0, api_op_GetSavingsPlansPurchaseRecommendation.go:34-94 and types/types.go:2444-2513, plus the primary request API and detail API. The SDK/API support the enums, pagination token, account identifier, optional string cost/utilization fields, and regional detail shape used here. This does not independently establish live billing economics.

Fresh macOS verification, pinned GOTOOLCHAIN=go1.26.9, GOWORK=off:

• AWS module: go build ./... and go test -race -short ./... passed. The first sandbox test attempt was blocked from binding local httptest ports; the normally approved rerun passed.
• Shared module: go build ./... and go test -race -count=1 ./ladder passed.
• Independently authored clean consumer: go test -race -count=1 -v ./... passed. Both shared and AWS modules resolve from published v0.0.0-20261015071854-5b254484d5e4, with no replace or workspace override. This explicitly exercises the public optional interface under real module resolution, rather than relying on the AWS module's older shared minimum pin.
• That consumer uses the actual SDK and factory with a synthetic local HTTP response. Different fixture values (4,6) and (24,6) across two pages produce 28/40 = 0.7; foreign-account and foreign-region details are excluded. It exercises factory -> rate capability -> Allocate -> BuildTranches -> stored-rate replay: $10/hour OD becomes approximately $7/hour commitment, Compute remains Hold, replay is a no-op, missing cost produces Hold, NaN produces a hard error, and mismatched scope fails before I/O.
• Three isolated mutations in an archived scratch copy each failed the intended assertion: bypassing the account guard failed TestGetCommitmentRates_ValidatesBeforeSource/account; removing factory rate wiring failed TestNewFromConfig_ValidatesAndScopesClients; dropping the continuation token failed the expected-rate assertion in TestCommitmentRates_PublicSDKConsumer. Each scratch mutation was restored. git diff --check passed and the source checkout remained clean.

Limits: responses are constructed SDK loopback fixtures, not recorded or live AWS account data. No real AWS API, purchase, deployment, or execution enablement occurred. Live cost-field economics remain the lower client's documented acceptance gap. This verdict covers only the SHA above; CI and merge authorization must be checked separately at merge time.

[cristim]

Dependency correction #405 merged as 8612582. The shared minimum now exposes the optional interface through a normal AWS-only installation. Independent replacement-free consumer proof and actual green CI are recorded on #405. This new parent head is undergoing retained independent exact-revision review and required CI before merge. @coderabbitai review

[coderabbitai]

@cristim I’ll review the updated PR, including the dependency correction from #405. Required CI remains a separate merge gate.

---

🧠 Learnings used

Learnt from: cristim
Repo: LeanerCloud/cloud-commitments-go PR: 404
File: providers/aws/go.mod:6-6
Timestamp: 2026-10-15T07:37:18.628Z
Learning: In LeanerCloud/cloud-commitments-go, validate the published providers/aws module with a clean consumer that requires only that module directly, with workspace mode disabled and no replacements. Import shared optional interfaces through the selected transitive pkg dependency. Requiring a newer pkg module directly can mask an outdated minimum pkg dependency in providers/aws/go.mod.

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[cristim]

Final exact-head independent adversarial verdict: no remaining actionable findings after two retained passes at 8612582b6e7ce6b584a43e96bcd07600fac2adcc, tree ba207c320b43c40492968a6714c333f50f22763c, base 29adce1c3883bfb71a926451c323eafea601e87f.

GitHub's Git commit API confirms that the final squash head has exactly the same tree as reviewed follow-up #405 (5bef0753ec018a1a8fa43490449430d65c08448b). I rebound both passes to the complete final PR diff against main: correctness/account scope/failure behavior and then completeness/security/bugs/reuse/complexity/scope. Runtime source and tests are unchanged from the original reviewed implementation; only the already-reviewed shared minimum and checksums changed. The source-of-truth review, full standalone race suite and three mutation detections remain applicable to that identical runtime source. The follow-up evidence closes the subsequently reproduced installation issue; it supersedes the earlier dual-pin consumer's incomplete coverage of that path.

Fresh final-head macOS proof, Go 1.26.9 and GOWORK=off: a new clean consumer initially required only published AWS v0.0.0-20261015075822-8612582b6e7c. go mod tidy naturally selected shared v0.0.0-20261015071854-5b254484d5e4. go list -m -json confirmed those versions with no replacements or workspace override; there was no manually supplied shared version. Both go build ./... and go test -race -count=1 -v ./... passed.

The named optional interface compiles, and the independent actual-SDK loopback consumer passes account/region exclusion, pagination and weighted 0.7 rate, scope rejection before I/O, $10 OD -> approximately $7 commitment, absent Compute Hold, missing-field Hold, malformed-field error, stored-rate tranche replay and no duplicate allocation. This is synthetic local HTTP evidence, not live AWS billing acceptance. No real AWS call, purchase, deployment or enablement occurred. Broad unchanged-source suites were not repeated solely for the squash SHA. CI and normal merge authorization remain separate gates for this exact head.

[cristim]

Final merge evidence covers head 8612582b6e7ce6b584a43e96bcd07600fac2adcc, tree ba207c320b43c40492968a6714c333f50f22763c, against unchanged main 29adce1c3883bfb71a926451c323eafea601e87f.

• Independent retained two-pass final review: no remaining actionable findings. A fresh published AWS-only consumer naturally selects the shared interface and passes build plus SDK loopback race tests, allocation and stored-rate replay. The runtime source is identical to the previously reviewed implementation; the dependency finding was fixed through merged follow-up fix(aws): expose rate interface through shared minimum #405.
• Required CI build/test run 38702381630 and pre-commit run 38702381639 both concluded SUCCESS. GitHub's official GraphQL API confirmed every check and both workflow-suite conclusions after the REST observer encountered a rate limit. The observer error was not a workflow failure.
• Fresh server state: exact head/base unchanged, MERGEABLE/CLEAN, aggregate SUCCESS, and all existing review threads resolved with linked fix evidence.

CodeRabbit posted “Review rate limited” on this final head. Its green status does not represent a fresh review. Its earlier dependency finding is fixed and independently verified; the repository's optional-review policy applies.

CR waived: quota, adversarial review + local verification + green CI

Evidence uses constructed local SDK HTTP responses, not live AWS billing acceptance. No purchase, deployment or execution enablement occurred. #349 stays open for matching-workload policy, residual baseline and E/k normalization, atomic platform units/rate persistence and the executor continuation. Runtime flags and schedulers remain off.

[cristim]

Independent post-merge published-consumer proof passed on macOS for main 9511dcf (tree ba207c320b43c40492968a6714c333f50f22763c).

Started a fresh module with only providers/aws v0.0.0-20261015081001-9511dcfbdcb1. Normal go mod tidy selected shared pkg v0.0.0-20261015071854-5b254484d5e4. go list -m -json confirmed both published versions and no Replace. No explicit initial shared pin or workspace was used.

With GOWORK=off and GOTOOLCHAIN=go1.26.9, under the three canonical retained-inode locks: go build ./... passed; go test -race -count=1 -v ./... passed (1.466s), including normal, missing, and malformed scenarios. The unchanged independent SDK loopback fixture covers account rejection before I/O, account/region filtering, pagination, optional interface satisfaction, EC2-only rates, Compute Hold, OD10 to commitment7, tranche conversion, and no-duplicate replay.

This is constructed local SDK transport evidence, not live AWS billing acceptance. No live AWS request or purchase occurred. No production files changed. CI and cleanup remain with the parent lane.