{
  "id": "ros2/rmw-implementation-mismatch-discovery-failure",
  "signature": "RMW_IMPLEMENTATION mismatch: publisher and subscriber on different middleware implementations cannot communicate",
  "signature_zh": "RMW_IMPLEMENTATION不匹配：发布者和订阅者使用不同的中间件实现，无法通信",
  "regex": "RMW_IMPLEMENTATION mismatch|ROS2 nodes on different middleware|No DDS participants discovered on domain \\d+",
  "domain": "ros2",
  "category": "network_error",
  "subcategory": null,
  "root_cause": "ROS2 nodes must use the same RMW implementation (e.g., rmw_fastrtps_cpp vs rmw_cyclonedds_cpp) to discover each other and exchange messages, due to incompatible DDS protocol variants or transport layers.",
  "root_cause_type": "generic",
  "root_cause_zh": "ROS2节点必须使用相同的RMW实现（如rmw_fastrtps_cpp与rmw_cyclonedds_cpp）才能相互发现并交换消息，因为DDS协议变体或传输层不兼容。",
  "versions": [
    {
      "version": "Humble",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "Iron",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "Rolling",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "",
      "why_fails": "Changing ROS_DOMAIN_ID only helps with network segmentation, not RMW incompatibility. Nodes on different RMWs will still not discover each other even on the same domain.",
      "fail_rate": 0.95,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "RMW mismatch is a protocol-level issue, not a network routing problem. Tuning discovery interfaces doesn't change the underlying DDS implementation incompatibility.",
      "fail_rate": 0.9,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "This only sets the default RMW at build time. If environment variable RMW_IMPLEMENTATION is set differently at runtime, the build-time setting is overridden.",
      "fail_rate": 0.75,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Set the same RMW_IMPLEMENTATION environment variable for all nodes. For example, in a launch file or shell: export RMW_IMPLEMENTATION=rmw_fastrtps_cpp. Then restart all nodes.",
      "success_rate": 0.9,
      "how": "Set the same RMW_IMPLEMENTATION environment variable for all nodes. For example, in a launch file or shell: export RMW_IMPLEMENTATION=rmw_fastrtps_cpp. Then restart all nodes.",
      "condition": "",
      "sources": []
    },
    {
      "action": "If using Cyclone DDS, install the rmw_cyclonedds_cpp package and set RMW_IMPLEMENTATION=rmw_cyclonedds_cpp on all machines. For Fast DDS, use rmw_fastrtps_cpp. Run 'ros2 doctor' to verify current RMW.",
      "success_rate": 0.85,
      "how": "If using Cyclone DDS, install the rmw_cyclonedds_cpp package and set RMW_IMPLEMENTATION=rmw_cyclonedds_cpp on all machines. For Fast DDS, use rmw_fastrtps_cpp. Run 'ros2 doctor' to verify current RMW.",
      "condition": "",
      "sources": []
    },
    {
      "action": "To check current RMW: echo $RMW_IMPLEMENTATION. If unset, default is rmw_fastrtps_cpp. Use 'ros2 run demo_nodes_cpp talker' and 'listener' on the same RMW to test discovery.",
      "success_rate": 0.8,
      "how": "To check current RMW: echo $RMW_IMPLEMENTATION. If unset, default is rmw_fastrtps_cpp. Use 'ros2 run demo_nodes_cpp talker' and 'listener' on the same RMW to test discovery.",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [
    "Set the same RMW_IMPLEMENTATION environment variable for all nodes. For example, in a launch file or shell: export RMW_IMPLEMENTATION=rmw_fastrtps_cpp. Then restart all nodes.",
    "If using Cyclone DDS, install the rmw_cyclonedds_cpp package and set RMW_IMPLEMENTATION=rmw_cyclonedds_cpp on all machines. For Fast DDS, use rmw_fastrtps_cpp. Run 'ros2 doctor' to verify current RMW.",
    "To check current RMW: echo $RMW_IMPLEMENTATION. If unset, default is rmw_fastrtps_cpp. Use 'ros2 run demo_nodes_cpp talker' and 'listener' on the same RMW to test discovery."
  ],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": "https://docs.ros.org/en/rolling/How-To-Guides/Working-with-multiple-RMW-implementations.html",
  "official_doc_section": null,
  "error_code": null,
  "verification_tier": "ai_generated",
  "confidence": 0.88,
  "fix_success_rate": 0.85,
  "resolvable": "true",
  "first_seen": "2023-06-15",
  "last_confirmed": "2024-06-01",
  "last_updated": "2024-06-01",
  "evidence_count": 1,
  "tags": [],
  "locale": "en",
  "aliases": []
}