[srstack]

Alternative to #76: keep azure-centralus a Filesystem-only placement instead of adding it to the shared placement table. The two changes conflict in internal/config/region; only one should merge.

Problem

ti fs --region azure-centralus ... fails local region validation even though the Azure Central US Filesystem deployment (https://azure-centralus.drive9.ai) is available.

region.supported is shared by Starter and Filesystem resolution, so only adding azure there also makes ti db accept the placement locally:

$ ti db create-db-cluster --db-cluster-type starter --db-cluster-name demo --region azure-centralus --dry-run
"region": { "name": "regions/azure-centralus" }   # EXIT=0, the request would be sent

README (Regions supporting TiDB Cloud Starter), docs/priciples.md, and the published regions page do not list Azure as a Starter placement, so that would send an unsupported region to the Starter API instead of failing locally.

Change

• internal/config/region: add ProviderAzure and the azure-centralus placement plus a filesystemOnly marker. Validate (Starter) rejects marked placements with placement "azure-centralus" serves TiDB Cloud Filesystem only, not TiDB Cloud Starter; the new ValidateFilesystem accepts them. ParsePlacementCode and CanonicalCode keep accepting every known placement, so --region, ti configure, profiles, and stored credentials are unaffected.
• internal/api/endpoints: Filesystem resolution uses ValidateFilesystem, and the built-in mapping gains azure-centralus -> https://azure-centralus.drive9.ai (mode=tidb_cloud_native).
• Telemetry: the CLI normalizer and the backend validator accept the azure provider and the azure-centralus region code.
• Docs and installers: README, docs/priciples.md, AGENTS.md, the telemetry backend design table, and the ti fs regions line of both installers.

Resulting behavior:

Command	Result
ti fs ... --region azure-centralus	routes to https://azure-centralus.drive9.ai (dry-run shows azure centralus)
ti db ... --region azure-centralus	config.invalid_region, exit 2, Filesystem-only message, no request sent
ti configure --region-code azure-centralus	accepted as a Filesystem placement

gcp-us-east1 intentionally keeps its current behavior here; applying the same Filesystem-only model to it is a separate decision, and the filesystemOnly marker makes that a one-line follow-up.

Verification

• gofmt -l is clean on the changed files, and go mod tidy leaves go.mod/go.sum unchanged.
• go test ./... passes.
• TI_E2E_BIN=bin/ti go test ./e2e/ passes except the pre-existing TestTelemetryUsesFakeIngestionServer, which also fails on unmodified main in this environment (local telemetry ingestion fixture, unrelated to this change).
• Binary probes:
  • ti --region azure-centralus fs create-file-system --dry-run -> "message": "azure centralus", /v1/admin/tenants, exit 0.
  • ti --region azure-centralus db create-db-cluster --db-cluster-type starter --db-cluster-name demo --dry-run -> ti [ERROR]: placement "azure-centralus" serves TiDB Cloud Filesystem only, not TiDB Cloud Starter, exit 2.
  • ti --region gcp-us-east1 db create-db-cluster ... --dry-run -> unchanged, still proceeds locally.
• New coverage: placement validation, built-in endpoint routing, Starter rejection at the CLI and against the compiled binary, stored credentials under an AWS-default profile, token-only companion routing with inherited DRIVE9_* isolation, and telemetry acceptance on both sides.

Follow-ups (not in this PR)

• The deployed ti-telemetry-backend must accept azure/azure-centralus before or with this CLI release. The column is an unconstrained VARCHAR(32), so no migration is needed.
• The published English ti regions page (docs/pingcap-docs/docs, ai/ti/reference/ti-regions-security-and-limitations.md) lives in a separate docs repo/submodule and is not updated here. It currently lists neither GCP nor Azure.
• The Azure Filesystem deployment itself was verified live in fix(fs): support Azure Central US with cloud routing regressions #76 (15/15 checks). This PR changes placement validation only, not the Filesystem transport.

[pingcap-cla-assistant]

All committers have signed the CLA.

[Copilot]

🔵 Needs a closer look

It alters core placement-validation semantics shared by ti db and ti fs and is an explicitly conflicting alternative to #76 where only one approach should merge, which is a human design decision.

0 open findings

What changed in this PR

This PR adds azure-centralus as a Filesystem-only placement. It is explicitly an alternative to #76: rather than adding Azure to the shared placement table (which would also make ti db accept it and send an unsupported region to the Starter API), it introduces a filesystemOnly marker so that ti fs accepts the placement while ti db rejects it locally with an explicit message. The change fits cleanly into the centralized internal/config/region placement model and the built-in Filesystem endpoint mapping, and it is threaded through telemetry (CLI + backend), docs, and installers.

Changes:

• Split region validation into Validate (Starter, rejects filesystem-only placements) and ValidateFilesystem (accepts them), with ParsePlacementCode/CanonicalCode now using a shared validatePlacement so --region, ti configure, profiles, and stored credentials accept every known placement.
• Routed ResolveFS through ValidateFilesystem and registered azure-centralus → https://azure-centralus.drive9.ai in the built-in FS region manifest.
• Accepted the azure provider and azure-centralus region in both the CLI telemetry normalizer and the backend validator, and updated README, docs/priciples.md, AGENTS.md, the telemetry design doc, and both installers.

File	Description
internal/​config/​region/​region.go	Adds Azure provider/prefix, filesystemOnly marker, and the Validate/ValidateFilesystem/validatePlacement split.
internal/​config/​region/​region_test.go	Covers filesystem-only acceptance for FS, Starter rejection, and placement parsing/canonical round-trips.
internal/​api/​endpoints/​endpoints.go	FS resolution uses ValidateFilesystem; built-in manifest gains the Azure Central US endpoint.
internal/​api/​endpoints/​endpoints_test.go	Verifies Azure FS routing and Starter rejection of the filesystem-only placement.
internal/​telemetry/​telemetry.go	Normalizer accepts the azure provider.
internal/​telemetry/​telemetry_test.go	Asserts Azure placement is preserved end-to-end.
internal/​telemetrybackend/​event.go	Backend validator allows azure provider and azure-centralus region.
internal/​telemetrybackend/​event_test.go	Parameterizes GCP/Azure acceptance; moves azure out of the rejected cases.
internal/​fs/​fscred/​credential_test.go	Confirms a filesystem-only region is stored/resolved without mutating profile placement.
internal/​cli/​root_test.go	CLI-level Starter rejection and FS dry-run acceptance for azure-centralus.
e2e/​cli_test.go	Compiled-binary routing to the Azure FS endpoint plus Starter rejection.
e2e/​installer_test.go	Installer region-listing assertions include azure-centralus.
README.md, docs/​priciples.md, AGENTS.md, docs/​telemetry-backend-design.md	Document the new Filesystem-only placement and provider mapping.
scripts/​install.sh, scripts/​install.ps1	Add azure-centralus to the printed ti fs regions list.

🧠 Review effort: Balanced

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[srstack]

Superseded by commit 4b7faa3 on the #76 branch (codex/azure-region-support), which now keeps azure-centralus a Filesystem-only placement. Closing this alternative so there is a single PR for the change.