Struct TopicRouter 

pub struct TopicRouter { /* private fields */ }

Pub/sub topic router for kernel IPC.

Manages subscriptions as a mapping from topic name to list of subscriber PIDs. Uses DashMap for lock-free concurrent access.

Dead subscriber cleanup

When a message is published, the router checks each subscriber’s state in the process table. Subscribers that have exited are automatically removed from the subscription list (lazy cleanup).

Implementations

impl TopicRouter

pub fn new(process_table: Arc<ProcessTable>) -> Self

Create a new topic router.

pub fn subscribe(&self, pid: Pid, topic: &str)

Subscribe a process to a topic.

If the process is already subscribed, this is a no-op.

pub fn unsubscribe(&self, pid: Pid, topic: &str)

Unsubscribe a process from a topic.

If the process is not subscribed, this is a no-op. Empty subscription lists are removed.

pub fn live_subscribers(&self, topic: &str) -> Vec<Pid>

Get the list of running subscribers for a topic.

Performs lazy cleanup: removes PIDs for processes that have exited. Returns only PIDs of running processes.

pub fn subscribers(&self, topic: &str) -> Vec<Pid>

Get all subscribers for a topic (including potentially dead ones).

Use TopicRouter::live_subscribers for a filtered list.

pub fn list_topics(&self) -> Vec<(String, usize)>

List all topics with their subscriber counts.

pub fn topics_for_pid(&self, pid: Pid) -> Vec<String>

List all topics a specific PID is subscribed to.

pub fn topic_count(&self) -> usize

Get the total number of active topics.

pub fn has_subscribers(&self, topic: &str) -> bool

Check whether a topic has any subscribers.

pub fn unsubscribe_all(&self, pid: Pid)

Remove all subscriptions for a PID (used during process cleanup).