Node Discovery & Monitoring

These types are for building custom monitoring and discovery tools. Most users don't need them — the built-in Monitor handles this automatically.

NodePresence

Node presence files written to shared memory for cross-process discovery. The scheduler creates these automatically at startup; monitoring tools read them. Paths are managed by horus_sys and vary by platform.

use horus::prelude::*; // NodePresence is available via the prelude

// Discover all running HORUS nodes on this machine
let nodes = NodePresence::read_all();
for node in &nodes {
    println!("{}: pid={}, rate={:?}Hz, health={:?}, ticks={}, errors={}",
        node.name(), node.pid(), node.rate_hz(),
        node.health_status(), node.tick_count(), node.error_count());
}

// Read a specific node
if let Some(motor) = NodePresence::read("motor_ctrl") {
    println!("Publishers: {:?}", motor.publishers());
    println!("Services: {:?}", motor.services());
}

Method	Returns	Description
`name()`	`&str`	Node name
`pid()`	`u32`	Process ID (verified for liveness)
`scheduler()`	`Option<&str>`	Scheduler name
`publishers()`	`&[TopicMetadata]`	Topics this node publishes
`subscribers()`	`&[TopicMetadata]`	Topics this node subscribes to
`rate_hz()`	`Option<f64>`	Configured tick rate
`health_status()`	`Option<&str>`	Healthy / Warning / Error / Critical
`tick_count()`	`u64`	Total ticks since start
`error_count()`	`u32`	Total errors since start
`services()`	`&[String]`	Provided services
`actions()`	`&[String]`	Provided actions

Static methods: read(name) → Option<Self>, read_all() → Vec<Self>

NodeAnnouncement

Real-time lifecycle events broadcast on the horus.ctl.{scheduler} topic. Unlike presence files (polled), announcements are push-based — you get notified the moment a node starts or stops.

// discovery module removed — node lifecycle managed via SchedulerRegistry + control topic
use horus::prelude::*;

let discovery: Topic<NodeAnnouncement> = Topic::new(DISCOVERY_TOPIC).unwrap();
if let Some(ann) = discovery.recv() {
    match ann.event {
        NodeEvent::Started => {
            println!("{} started (pid={})", ann.name, ann.pid);
            println!("  publishes: {:?}", ann.publishers);
            println!("  subscribes: {:?}", ann.subscribers);
        }
        NodeEvent::Stopped => println!("{} stopped", ann.name),
    }
}

Field	Type	Description
`name`	`String`	Node name
`pid`	`u32`	Process ID
`event`	`NodeEvent`	`Started` or `Stopped`
`publishers`	`Vec<String>`	Published topic names
`subscribers`	`Vec<String>`	Subscribed topic names
`timestamp_ms`	`u64`	Event timestamp

Node Discovery & Monitoring

NodePresence

NodeAnnouncement

See Also