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

1. 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.

1. 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.

1. Apply framework-aligned migrations

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

1. 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:

• [references/316-frameworks-spring-mongodb-migrations-mongock.md](references/316-frameworks-spring-mongodb-migrations-mongock.md)
• [references/316-frameworks-spring-mongodb-migrations-mongock-antipatterns.md](references/316-frameworks-spring-mongodb-migrations-mongock-antipatterns.md)
• [references/316-frameworks-spring-mongodb-migrations-mongock-parallel-change.md](references/316-frameworks-spring-mongodb-migrations-mongock-parallel-change.md)