fix(gcp): stop retaining the VPC and subnet so a failed down surfaces

[defangdevs]

Closes #183. Supersedes #462, which put the retry logic in the CD; the CLI now owns it (DefangLabs/defang#2157).

The rule

RetainOnDelete is only legitimate where a recipe deliberately keeps a non-defang resource — a built image, a customer's bucket, a DNS zone the customer owns. Everywhere else it is a leak generator, because it deletes the resource from the Pulumi state file: the down reports success, the resource stays in the cloud, and no later down has anything left to delete.

None of the GCP retains met that bar. provider/defanggcp now has no RetainOnDelete at all.

The leak this fixes

The VPC and its subnet were retained, so every defang down reported success and left the network standing. The project eventually ran into its NETWORKS quota. That is issue #183.

Now the destroy fails instead. The failure is expected, not exceptional: Cloud Run attaches to the subnet with Direct VPC egress (buildVpcAccess, cloudrun.go) and GCP holds the subnet's IP addresses for 1-2 hours after the service is gone:

"After you delete or move your Cloud Run resources, wait 1-2 hours for Cloud Run to release the IP addresses before you delete the subnet."
— Cloud Run Direct VPC docs

Nothing can wait that out inside an apply. So the down fails, the CLI starts the AI debugger, the debugger runs the GCP cleanup tool added in DefangLabs/defang#2157, and the tool removes the peering, the reserved range, the subnet and the network through the Compute API. A later defang down then completes.

Resource by resource

VPC and subnet (gcp/gcp.go) — retain removed, as above.

Service Networking connection (gcp/vpc_peering.go) — DeletionPolicy: "ABANDON" replaces the retain. The provider's delete calls servicenetworking deleteConnection, which cannot be relied on for two independent reasons:

• GCP requires every service instance to be gone before the connection goes, and producer-side cleanup lags the instance delete by up to 4 days for Cloud SQL (private services access docs).
• google_service_networking_connection uses servicenetworking.delete when google console utilizes networks.removePeering hashicorp/terraform-provider-google#18834, still open, records that Google's own console removes the peering through the Compute API instead. A maintainer there offers exactly two options: abandon state, or restore removePeering.

ABANDON skips the doomed call so Pulumi can finish the rest of the teardown; the CLI then calls compute.networks.removePeering. The field is Optional+Computed and not ForceNew, so it updates in place on an existing stack and never replaces the peering.

MIG instance template (gcp/compute.go) — retain removed. The legacy CD added it to dodge "The instance_template resource is already being used by", which the delete half of a replacement can raise while the MIG still points at the old template. That traded one error for two leaks: a template per redeploy, and a template left holding the subnet on teardown. If the replace error comes back, the fix is the ordering, not the symptom.

Enabled APIs (gcp/gcp.go, project.go) — DisableOnDestroy: false replaces the retain. This one is not a leak fix: both options leave the API enabled after a down, and both drop the resource from Pulumi state. The point is to use the provider's own switch for exactly this intent, so that RetainOnDelete is left meaning only the one thing it should mean.

Cloud SQL user and database (gcp/cloudsql.go) — retain removed, DeletionPolicy: ABANDON kept. Also not a leak fix: deleting the instance removes its users and databases, so there is nothing here to delete and nothing to leak. The retain was simply redundant with the deletion policy, which already suppresses the API call.

Trade-off to be aware of

A GCP down inside the 1-2 hour window now fails where it used to report success. That is the point — the leak was the silence — but it is a visible behaviour change, and the good outcome depends on DefangLabs/defang#2157 shipping alongside it.

Stacks whose state predates this change

retainOnDelete is recorded per resource in the checkpoint, and pulumi destroy does not re-run the program, so removing it in provider code changes nothing for a stack whose current state was written by the old code. Those stacks still down "successfully" and still leak. The CLI cleanup tool covers them, because it finds orphans through the GCP API by network-name prefix rather than through Pulumi state.

Not in scope

AWS and Azure still carry retains. The recipe-driven ones (RetainBucketOnDelete, RetainDnsOnDelete) are exactly the legitimate case. The unconditional ones are worth their own pass: defangaws/aws/cert.go:241, defangaws/aws/route53.go:83, defangaws/aws/infra.go:150, defangazure/azure/keyvault.go:83, defangazure/project.go:315. The Artifact Registry retain is #457's subject.

Testing

go test ./provider/... and cd tests && go test -short ./... are green. No test asserted on the retain flags.

End-to-end verification is a real GCP up / down cycle against a CD image built from this branch; that is in progress separately.

Summary by CodeRabbit

• Bug Fixes

  • Improved cleanup of VPCs, subnets, and VPC peering connections by removing unexpected resource retention.
  • Prevented instance templates from being retained after deletion, reducing template leaks and teardown failures.
  • Improved cleanup behavior for cloud services, databases, and database users while preserving required services.
  • Replacement failures now surface through resource ordering rather than being masked by retained resources.

• Documentation

  • Added guidance explaining instance template retention changes and recommended resource ordering.

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📝 Walkthrough

Walkthrough

The provider removes Pulumi retention from GCP resources. APIs remain enabled on destroy. VPC peering and Cloud SQL resources use ABANDON deletion policies. Instance templates no longer remain retained after deletion.

Changes

GCP deletion policies

Layer / File(s)	Summary
Network resource deletion behavior provider/defanggcp/gcp/gcp.go, provider/defanggcp/gcp/vpc_peering.go	VPCs and subnets use the supplied resource options. VPC peering sets the service connection deletion policy to ABANDON.
Service resource deletion behavior provider/defanggcp/gcp/gcp.go, provider/defanggcp/project.go, provider/defanggcp/gcp/cloudsql.go	API services remain enabled on destroy without Pulumi retention. Cloud SQL users and databases use ABANDON without Pulumi retention.
Instance template cleanup provider/defanggcp/gcp/compute.go	Instance templates no longer use Pulumi retention. Comments describe cleanup during replacement and teardown.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to a21b9

This change removes unintended GCP resource retention and routes expected cleanup behavior through the existing teardown flow; no actionable merge-blocking risk remains based on the supplied evidence.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 83.33% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 5 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the primary VPC and subnet retention change and its effect on failed cleanup operations.

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Actionable comments posted: 1

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Inline comments:
In `@provider/defanggcp/gcp/gcp.go`:
- Around line 65-72: Update the comments around the API service options in
provider/defanggcp/gcp/gcp.go lines 65-72 and provider/defanggcp/gcp/cloudsql.go
lines 173-178 to accurately state that RetainOnDelete skips the provider delete
call and removes the resource from Pulumi state, leaving the cloud resource
unmanaged; distinguish this behavior from DisableOnDestroy and DeletionPolicy:
"ABANDON".

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📒 Files selected for processing (4)

• provider/defanggcp/gcp/cloudsql.go
• provider/defanggcp/gcp/compute.go
• provider/defanggcp/gcp/gcp.go
• provider/defanggcp/project.go

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