fix: Preserve mongo_db_major_version state after out-of-band major version upgrade by marcabreracast · Pull Request #4400 · mongodb/terraform-provider-mongodbatlas

marcabreracast · 2026-04-23T09:30:20Z

Description

Fixes a bug where mongodbatlas_advanced_cluster would retain a stale mongo_db_major_version in Terraform state after an out-of-band major version upgrade (e.g. upgrading from MongoDB 7.0 to 8.0 via Atlas UI and unpinning FCV). Even after updating the config to match the new version, the provider would perpetually show a diff.

The root cause was in overrideAttributesWithPrevStateValue: it unconditionally overwrote the API value with the prior state value whenever they differed, which was intended to suppress cosmetic formatting differences (e.g. "8" vs "8.0") but also masked real version transitions.

The fix narrows the override to cases where the major component is the same, handling two scenarios: formatting differences (e.g. "8" vs "8.0") and minor version bumps from version_release_system = "CONTINUOUS" (e.g. "8.0" vs "8.2") where the version is no longer user-controlled.

Link to any related issue(s): CLOUDP-399538

Closes #4398

Type of change:

Bug fix (non-breaking change which fixes an issue). Please, add the "bug" label to the PR.
New feature (non-breaking change which adds functionality). Please, add the "enhancement" label to the PR. A migration guide must be created or updated if the new feature will go in a major version.
Breaking change (fix or feature that would cause existing functionality to not work as expected). Please, add the "breaking change" label to the PR. A migration guide must be created or updated.
This change requires a documentation update
Documentation fix/enhancement

Required Checklist:

I have signed the MongoDB CLA
I have read the contributing guides
I have checked that this change does not generate any credentials and that they are NOT accidentally logged anywhere.
I have added tests that prove my fix is effective or that my feature works per HashiCorp requirements
I have added any necessary documentation (if appropriate)
I have run make fix and verified my code
If changes include deprecations or removals I have added appropriate changelog entries.
If changes include removal or addition of 3rd party GitHub actions, I updated our internal document. Reach out to the APIx Integration slack channel to get access to the internal document.

Further comments

Related external PR: #4399 (opened by the issue reporter with the same fix — this PR adapts it to follow our internal conventions).

…ccess

Copilot

Pull request overview

This PR adjusts advanced cluster state reconciliation so MongoDB major version values are only preserved from prior state when the difference is purely formatting (e.g., "8" vs "8.0"), while allowing real major-version transitions reported by the Atlas API to be reflected in Terraform state.

Changes:

Updates overrideAttributesWithPrevStateValue to preserve mongo_db_major_version only for formatting-only diffs.
Introduces ShouldUsePreviousMongoDBMajorVersion helper encapsulating the formatting comparison logic.
Adds a unit test covering the helper’s expected behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
`internal/service/advancedcluster/resource_compatiblity.go`	Refines state override logic for `mongo_db_major_version` and adds a helper for formatting-only comparisons.
`internal/service/advancedcluster/resource_compatiblity_test.go`	Adds unit test coverage for the new helper behavior.

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marcabreracast · 2026-04-24T09:32:57Z

 	modelOut.UseEffectiveFields = modelIn.UseEffectiveFields
 }

+func ShouldUsePreviousMongoDBMajorVersion(beforeVersion, afterVersion string) bool {


This function helps preserve the prior state value when the major component is the same, which handles two cases:

Formatting differences: user sets "8" but Atlas returns "8.0" which is the same version, but different format. This is to preserve SDKv2 behaviour

version_release_system = "CONTINUOUS": Atlas can return a minor bump (e.g. "8.2") that is not user-controlled. Letting it through causes: provider produced an unexpected new value: .mongo_db_major_version: was cty.StringVal("8.0"), but now cty.StringVal("8.2"). `

The reason why step 2 is implemented, is to avoid unit test failure

github-actions · 2026-04-24T09:35:10Z

APIx bot: a message has been sent to Docs Slack channel

augmentcode · 2026-04-24T09:37:53Z

🤖 Augment PR Summary

Summary: Fixes perpetual plan drift for mongodbatlas_advanced_cluster when mongo_db_major_version changes out-of-band (e.g., via Atlas UI).

Changes:

Narrows the state-override logic to only keep the prior version when the major component matches (avoids masking real major upgrades).
Adds helpers to normalize/compare version major components.
Adds unit tests covering formatting differences, real major transitions, and same-major minor drift.

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augmentcode

Review completed. 2 suggestions posted.

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augmentcode · 2026-04-24T09:37:54Z

 	beforeVersion := conversion.NilForUnknown(modelIn.MongoDBMajorVersion, modelIn.MongoDBMajorVersion.ValueStringPointer())
-	if beforeVersion != nil && !modelIn.MongoDBMajorVersion.Equal(modelOut.MongoDBMajorVersion) {
+	afterVersion := conversion.NilForUnknown(modelOut.MongoDBMajorVersion, modelOut.MongoDBMajorVersion.ValueStringPointer())
+	// Only preserve prior state value for formatting differences (e.g. "8" vs "8.0"), not real version transitions.


internal/service/advancedcluster/resource_compatiblity.go:99 — This comment says the override is only for formatting differences, but ShouldUsePreviousMongoDBMajorVersion also preserves the prior value when the minor version changes within the same major (e.g., CONTINUOUS returning 8.2). Consider clarifying the comment so future readers don’t assume this logic is formatting-only.

Severity: low

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augmentcode · 2026-04-24T09:37:54Z

+)
+
+func TestAdvancedCluster_ShouldUsePreviousMongoDBMajorVersion(t *testing.T) {
+	testCases := []struct {


internal/service/advancedcluster/resource_compatibility_test.go:11 — The table covers major-change vs same-major outcomes, but it doesn’t exercise the beforeVersion == afterVersion early-return branch in ShouldUsePreviousMongoDBMajorVersion. Consider adding an explicit equality case to lock in that behavior.

Severity: low

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EspenAlbert

Nice! Really good PR description 👏

AgustinBettati

Changes LGTM, would just confirm with Alex and team on potential impact

AgustinBettati · 2026-04-24T14:22:07Z

+	return majorComponent(beforeVersion) == majorComponent(afterVersion)
+}
+
+func majorComponent(version string) string {


Users that have an outdate mongo_db_major_version value would now receive a non-empty plan (cases where major version upgrade was done outside of TF). Would confirm with Alex we are okay with this impact.

AgustinBettati · 2026-04-24T14:25:19Z

+	return majorComponent(beforeVersion) == majorComponent(afterVersion)
+}
+
+func majorComponent(version string) string {


q: Does version_release_system = "CONTINUOUS" only upgrade minor versions?

Both, per my understanding of the docs:

Latest Version With Auto Upgrades: If you set your cluster to this release option, it receives automatic upgrades to the latest available MongoDB major or minor version

Okay, would make sure to test if an error is returned if version_release_system = "CONTINUOUS" and mongo_db_major_version attribute are used together (as per our docs). Using this combination would lead to non-empty plan once automatic major version upgrades are made.

jromo-mdb

LGTM

mkusaka and others added 2 commits April 23, 2026 10:51

fix: preserve api mongo_db_major_version on real upgrades

32ca815

Fix lint issue by using correct package and update function to give a…

93cbb4d

…ccess

Copilot AI review requested due to automatic review settings April 23, 2026 09:30

github-actions Bot added the bug label Apr 23, 2026

Copilot started reviewing on behalf of marcabreracast April 23, 2026 09:30 View session

Add changelog

5d1bfd1

marcabreracast changed the title ~~fix: Preserve mongo db major version outbound upgrades~~ fix: Preserve mongo_db_major_version state after out-of-band major version upgrade Apr 23, 2026

Copilot AI reviewed Apr 23, 2026

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Comment thread internal/service/advancedcluster/resource_compatibility_test.go

Comment thread internal/service/advancedcluster/resource_compatiblity_test.go Outdated

marcabreracast added 2 commits April 23, 2026 11:39

Rename file due to typo and address PR comments

0b83ff7

Add case to use major component comparison to avoid inconsistency errors

e3afc28

This was referenced Apr 23, 2026

[Bug]: mongodbatlas_advanced_cluster keeps previous mongo_db_major_version in state after out-of-band major upgrade #4398

Open

fix: preserve api mongo_db_major_version on real upgrades #4399

Closed

marcabreracast commented Apr 24, 2026

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marcabreracast marked this pull request as ready for review April 24, 2026 09:34

marcabreracast requested review from a team as code owners April 24, 2026 09:34

augmentcode Bot reviewed Apr 24, 2026

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EspenAlbert approved these changes Apr 24, 2026

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AgustinBettati reviewed Apr 24, 2026

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Rephrase changelog for clarity

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jromo-mdb approved these changes Apr 24, 2026

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