recovery-behavior-tree

Use a RecoveryNode with two children: the normal navigation pipeline on the left and recovery actions on the right. When navigation fails, the recovery branch runs actions like clearing costmaps, spinning, or backing up, then retries navigation up to the configured number_of_retries.

PipelineSequence re-ticks all previous children when a later child is ticked, enabling the planner to re-plan while the controller follows the path. A standard Sequence ticks children strictly in order without re-execution, so it cannot support continuous replanning.

Infinite recovery loops happen when recovery always succeeds but navigation always fails, such as with an unreachable goal. Set number_of_retries to a reasonable value like 3-6 and let failure propagate to a higher-level tree that can select a different goal.

Place a GoalUpdated node as the first child of a ReactiveFallback wrapping your recovery actions. When a new goal arrives, GoalUpdated returns SUCCESS, short-circuiting the recovery so the tree immediately retries navigation toward the new goal.

Nav2 provides ClearEntireCostmap for resetting global and local costmaps, Spin for rotating in place, Wait for pausing while obstacles clear, and BackUp for reversing a fixed distance. These are typically cycled through a RoundRobin node with escalating aggressiveness.