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A2: Supervisor Nodes and Recovery

Status: Content in development. See Advanced Exercises for hands-on practice with this topic.

Learning Objectives​

By the end of this lesson, you will be able to:

  • Design and implement supervisor node architectures
  • Implement automatic recovery strategies
  • Handle state persistence and restoration
  • Implement graceful degradation patterns
  • Build emergency stop mechanisms

Introduction​

Detecting failures is only half the battle - your system must also recover from them automatically. This lesson teaches you how to build supervisor nodes that oversee system operation and implement intelligent recovery strategies to maintain continuous operation.

Coming Soon​

This lesson is currently under development. In the meantime:

  1. Review Prerequisites: Ensure you completed A1: Watchdogs and Health Monitoring

  2. Practice with Exercises: Complete Exercise 02: Supervisor Node with Recovery which provides detailed implementation guidance

  3. Explore AI Prompts: Use Advanced AI Prompts for supervisor and recovery help

  4. Study Patterns: Review recovery patterns in production robotics literature

Planned Topics​

This lesson will cover:

1. Supervisor Architecture​

  • Supervisor node responsibilities
  • Monitoring vs. control separation
  • Hierarchical supervision
  • Distributed supervision patterns

2. Recovery Strategies​

  • Restart: When and how to restart failed nodes
  • Fallback: Switching to simpler behaviors
  • Safe Mode: Stopping safely and waiting for intervention
  • Escalation: When to involve human operators

3. State Persistence​

  • What state to persist
  • Where to store state (files, databases, parameters)
  • State restoration on recovery
  • Handling corrupted state

4. Graceful Degradation​

  • Identifying critical vs. non-critical components
  • Degraded operation modes
  • Performance vs. safety trade-offs
  • User notification strategies

5. Emergency Stop​

  • Implementing reliable e-stop mechanisms
  • Hardware vs. software e-stop
  • E-stop propagation through system
  • Recovery from e-stop

6. Recovery Testing​

  • Fault injection for testing
  • Recovery time measurement
  • Stress testing recovery mechanisms
  • Validation and verification

Resources​

While this lesson is in development, use these resources:

  • Lifecycle Nodes: https://design.ros2.org/articles/node_lifecycle.html
  • Fault Tolerance Patterns: Academic papers on fault-tolerant robotics
  • Production Case Studies: Industry examples of recovery systems
  • Safety Standards: ISO 13849, IEC 61508 for safety-critical systems

Next Steps​

Continue to A3: Continuous Operation or practice with Advanced Exercises