ProcOrDial Router#

ProcOrDial is a specialized router that bridges the service proc, local proc, and the DialMailboxRouter. It enables bidirectional routing in the Host by distinguishing between messages destined for the service proc, local proc, versus those targeting spawned procs.

Structure#

struct ProcOrDial {
    service_proc: Proc,              // The service proc
    local_proc: Proc,                // The local proc
    dialer: DialMailboxRouter,       // Router for spawned procs
}

Routing Logic#

ProcOrDial implements MailboxSender with conditional routing based on the destination:

impl MailboxSender for ProcOrDial {
    fn post_unchecked(&self, envelope: MessageEnvelope, ...) {
        if envelope.dest().actor_id().proc_id() == self.service_proc.proc_id() {
            self.service_proc.post_unchecked(envelope, ...)  // → service proc
        } else if envelope.dest().actor_id().proc_id() == self.local_proc.proc_id() {
            self.local_proc.post_unchecked(envelope, ...)    // → local proc
        } else {
            self.dialer.post_unchecked(envelope, ...)        // → dialed procs
        }
    }
}

When a message arrives:

Check destination: Is it addressed to the service proc’s ProcId?
Route to service proc: If yes, deliver directly to service_proc
Check local proc: Is it addressed to the local proc’s ProcId?
Route to local proc: If yes, deliver directly to local_proc
Route via dialer: Otherwise, forward to DialMailboxRouter which looks up the target proc and dials its backend address

Integration with Host#

Both the frontend and backend receivers in Host are served by ProcOrDial:

// Backend receiver (from spawned procs)
let _backend_handle = host.forwarder().serve(backend_rx);

// Frontend receiver (from external clients)
Some(self.forwarder().serve(self.frontend_rx.take()?))

This creates a unified routing layer where all incoming messages flow through the same router, regardless of their source.

Bidirectional Routing#

The ProcOrDial router enables complete bidirectional communication:

Inbound Messages#

From external clients (frontend_rx):

→ ProcOrDial
→ service proc (if dest matches) OR local proc (if dest matches) OR spawned proc (via DialMailboxRouter)

From spawned procs (backend_rx):

→ ProcOrDial
→ service proc (if dest matches) OR local proc (if dest matches) OR other spawned procs (via DialMailboxRouter)

Outbound Messages#

From service proc or local proc:

Uses DialMailboxRouter as its forwarder
→ looks up proc by name in address book
→ dials backend address
→ delivers to target proc

This symmetric design allows procs to communicate freely - external clients can reach any proc, spawned procs can reach each other or the service/local procs, and the service/local procs can coordinate across all spawned procs.