Spring - MongoDB migrations (Mongock)

Apply Mongock migration guidelines for Spring Boot and Spring Data MongoDB.

What is covered in this Skill?

Mongock BOM, Spring Boot runner, and Spring Data MongoDB driver coordinates
mongock.migration-scan-package configuration and startup execution
Code-first @ChangeUnit migrations with @Execution and rollback hooks
Locking, idempotency, transaction limits, and forward-only rollout discipline
Optional MongoDB-backed integration tests using only project-approved, pinned, or already-available container images when the user permits external runtime dependencies
Coordination with @315-frameworks-spring-mongodb

Scope: Apply recommendations based on the reference rules and good/bad examples.

Constraints

Compile before Mongock or MongoDB migration changes; verify after changes.

MANDATORY: Run ./mvnw compile or mvn compile before applying any change
SAFETY: If compilation fails, stop immediately
VERIFY: Run ./mvnw clean verify or mvn clean verify after applying improvements
BEFORE APPLYING: Read the reference for detailed rules and good/bad patterns
EDGE CASE: If the project Spring Data MongoDB version is not compatible with the selected Mongock driver, stop and ask whether to pin/upgrade Mongock or use a lower driver generation
EXTERNAL RUNTIME GATE: Do not pull or execute Docker images for MongoDB verification unless the user explicitly approves and the image is pinned, policy-approved, or already present in the project configuration

When to use this skill

Add Mongock migrations in Spring Boot
Review Spring MongoDB data migrations
Configure Mongock change units for Spring Data MongoDB
Create Mongock change units for Spring Boot MongoDB
Review Mongock migration ordering in a Spring service

Workflow

Read references and inspect MongoDB setup

Read references/316-frameworks-spring-mongodb-migrations-mongock.md, references/316-frameworks-spring-mongodb-migrations-mongock-antipatterns.md, and references/316-frameworks-spring-mongodb-migrations-mongock-parallel-change.md, then inspect pom.xml, Spring Boot version, dependency management, MongoDB configuration, existing full-context tests, and existing @315-frameworks-spring-mongodb persistence patterns.

Choose runner, driver, and execution policy

Select Mongock coordinates compatible with the active Spring Data MongoDB generation, configure migration scan packages, and decide startup vs controlled-job execution.

Apply framework-aligned migrations

Implement/refactor @ChangeUnit classes with idempotent operations, explicit ordering, rollback hooks, and safe lock/transaction settings.

Run verification and report results

Execute build/tests. Run MongoDB-backed migration checks only when the project already defines an approved MongoDB test runtime or the user explicitly approves a pinned container image. If generic @SpringBootTest smoke tests do not provide MongoDB, disable Mongock only for those tests with mongock.enabled=false. Summarize outcomes and follow-up risks.

Reference

For detailed guidance, examples, and constraints, see: