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Coordination

The coordination layer lets drones share state with each other and the GCS without a central broker. Each robot periodically broadcasts a PeerProfile — its GPS position, heading, current waypoint, and any custom data payloads — over a shared DDS domain. Every robot and the GCS receives every other robot's profile directly.

Architecture

Robot 1 (domain 1)          Shared gossip domain (99)          GCS (domain 0)
┌──────────────────┐         ┌─────────────────────┐         ┌──────────────┐
│  gossip_node     │──────▶  │   /gossip/peers      │ ──────▶│  GCS         │
│  publishes own   │         │                      │        │  visualizer  │
│  PeerProfile     │ ◀──────  │  (all robots + GCS   │        └──────────────┘
│                  │         │   subscribe here)    │
│  local registry  │         └─────────────────────┘
│  (read-only)     │
└──────────────────┘
         ▲
    DDS Router
    bridges domain 1
    ↔ domain 99

Each robot builds a local registry of all known peers from incoming messages. The registry never leaves the robot — only each drone's own profile is transmitted.

PeerProfile

Every message on /gossip/peers is a PeerProfile containing:

Field Type Description
robot_name string Unique robot identifier
gps_fix NavSatFix Current GPS position (also used as message ID for dedup)
heading float64 Compass heading, degrees CW from North
waypoint PoseStamped Current navigation goal (all-zeros = no plan)
payloads PeerProfilePayload[] Arbitrary serialized ROS messages
source uint8 0 = direct, 1 = relayed (reserved)
relay_hops uint8 Hop count (reserved)

Launch

Coordination is included in the main autonomy bringup automatically. To launch standalone:

ros2 launch coordination_bringup gossip.launch.xml

Key parameters:

Parameter Default Description
robot_name $ROBOT_NAME Robot identifier and topic namespace
publish_rate 1.0 Publish rate in Hz (wall-clock)
gossip_domain 99 Shared DDS domain

Monitoring

# Live peer registry in the terminal
ROS_DOMAIN_ID=99 ros2 run coordination_bringup peer_registry_monitor

# Filter to one robot
ROS_DOMAIN_ID=99 ros2 run coordination_bringup peer_registry_monitor --robot robot_1

# Inspect raw messages
ros2 topic echo /gossip/peers