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I3: Inter-Node Communication Patterns

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

Learning Objectives​

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

  • Choose appropriate communication patterns for different scenarios
  • Design effective message structures for workflows
  • Configure QoS profiles for reliability
  • Implement synchronization between nodes
  • Handle communication failures gracefully

Introduction​

Effective inter-node communication is crucial for robust workflows. This lesson covers the patterns, best practices, and trade-offs for different communication approaches in ROS 2 workflows.

Coming Soon​

This lesson is currently under development. In the meantime:

  1. Review Prerequisites: Ensure you completed I2: Multi-Node Pipelines

  2. Practice with Exercises: Complete Exercise 04: Debug a Broken Workflow and the Capstone Project

  3. Explore AI Prompts: Use Intermediate AI Prompts for communication pattern help

  4. Review Chapter 1: Revisit ROS 2 communication fundamentals from Chapter 1

Planned Topics​

This lesson will cover:

1. Communication Pattern Selection​

  • Topics vs. Services vs. Actions
  • Decision criteria and trade-offs
  • When to use each pattern
  • Common anti-patterns to avoid

2. Message Design​

  • Designing effective message structures
  • Standard message types vs. custom messages
  • Message versioning and compatibility
  • Performance considerations

3. Quality of Service (QoS)​

  • QoS profiles explained
  • Reliability settings (reliable vs. best effort)
  • History settings (keep last vs. keep all)
  • Durability and liveliness
  • Choosing QoS for different scenarios

4. Synchronization Patterns​

  • Time synchronization between nodes
  • Message synchronization (ApproximateTime, ExactTime)
  • Handling different publishing rates
  • Buffering and queuing strategies

5. Error Handling​

  • Detecting communication failures
  • Timeout handling
  • Retry strategies
  • Fallback behaviors

Resources​

While this lesson is in development, use these resources:

Next Steps​

Complete the Intermediate Capstone Project or proceed to Advanced Tier