Gazebo Rollback Safety After SDF Schema Updates: Version Mismatch Behavior

Question

Goal
Developers often rely on Gazebo’s World::Save and World::Load APIs to capture and restore simulation states. When the underlying SDF schema evolves—such as adding new elements or deprecating old ones—the snapshot contains the original SDF version. Gazebo’s load routine compares this stored version against the current simulator’s expected schema and aborts the restore if they differ, preventing silent corruption.
Unresolved Decision
There is currently no automated migration path for older snapshots to the new schema. The documentation notes that developers can write custom migration scripts, but the core library offers no built‑in solution. Consequently, any automated test or long‑running simulation that expects a silent rollback after an SDF upgrade may encounter a hard failure.
Specific Questions

Does Gazebo provide any internal mechanism or flag to bypass or adapt the version check during World::Load?
What are the documented best practices for maintaining rollback compatibility across SDF schema changes, and are there recommended migration patterns?
Is there a plan in the Gazebo roadmap to introduce automated snapshot migration or a more flexible version‑compatibility layer?

Tasadduq Burney · Answer

Direct Answer
No. Gazebo’s World::Load does not provide a flag, environment variable, or internal mechanism to bypass or adapt the SDF version check. If the SDF version stored in a saved snapshot differs from the schema expected by the running simulator, the load aborts with an error before the world is fully restored.

Confirmed Behavior and Scope
In Gazebo 11 and the Ignition Gazebo line, the version comparison is a hard gate. The saved file carries its original <sdf version='...'> attribute, and World::Load compares that value against the simulator’s expected SDF schema. A mismatch causes a load failure rather than a silent upgrade or downgrade. This is deliberate: skipping the check risks missing elements, defaulted parameters, or undefined physics behavior.
Because Gazebo evolves, treat the “no bypass” conclusion as a strong default that still warrants source-level verification for any release newer than the 11/Ignition era.

Best Practices for Rollback Compatibility

Keep snapshots version-consistent. Save and restore with the same Gazebo/SDF build whenever possible. This avoids the version gate entirely.
Write custom migration scripts. When a snapshot must move to a newer schema, use the sdf::Root API to load the SDF DOM, update the version attribute, and transform added, removed, or deprecated elements into their current equivalents before calling World::Load.
Never hand-edit only the version string. Changing the version attribute without adjusting the underlying elements can silently introduce incorrect model parameters or corrupt simulation state.

Roadmap and Tooling
As of Gazebo 11 and Ignition Gazebo, the core library does not include an automated snapshot migrator or a flexible version-compatibility layer. The roadmap does not commit to a built-in migration tool; the responsibility remains with user-provided scripts or external tooling.

Practical Verification

Inspect the World::Load implementation in your target release (for example, gazebo/physics/World.cc in the classic stack) to confirm the version comparison logic.
Run a controlled test: save a world with one build, edit the saved SDF’s version to an older value, and attempt to load it with a newer build to observe the abort.
Review SDF versioning tutorials and release notes for your specific version to confirm whether any migration helpers have been introduced.

Gazebo Rollback Safety After SDF Schema Updates: Version Mismatch Behavior

Goal

Unresolved Decision

Specific Questions

1 answer

Direct Answer

Confirmed Behavior and Scope

Best Practices for Rollback Compatibility

Roadmap and Tooling

Practical Verification

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