Add mDNS republish logic with exponential backoff

src/server/mdns.ts

@@ -4,7 +4,12 @@ import { LOCAL_HOST } from '%config'
 import { networkInterfaces } from 'os'
 import { hostLog } from './tui'
 
+const MAX_REPUBLISH_DELAY = 30_000
+const REPUBLISH_BASE_DELAY = 1_000
+
+const _killed = new Set<string>()
 const _publishers = new Map<string, Subprocess>()
+const _republishAttempts = new Map<string, number>()
 
 const isEnabled = process.env.NODE_ENV === 'production' && process.platform === 'linux'
 
@@ -51,10 +56,12 @@ export function publishApp(name: string) {
     })
 
     _publishers.set(name, proc)
+    _republishAttempts.delete(name)
     hostLog(`mDNS: published ${host} -> ${ip}`)
 
     proc.exited.then(() => {
       _publishers.delete(name)
+      if (!_killed.delete(name)) republish(name)
     })
   } catch {
     hostLog(`mDNS: failed to publish ${host}`)
@@ -64,9 +71,11 @@ export function publishApp(name: string) {
 export function unpublishApp(name: string) {
   if (!isEnabled) return
 
+  _republishAttempts.delete(name)
   const proc = _publishers.get(name)
   if (!proc) return
 
+  _killed.add(name)
   proc.kill()
   _publishers.delete(name)
   hostLog(`mDNS: unpublished ${toSubdomain(name)}.${LOCAL_HOST}`)
@@ -75,9 +84,20 @@ export function unpublishApp(name: string) {
 export function unpublishAll() {
   if (!isEnabled) return
 
+  _republishAttempts.clear()
   for (const [name, proc] of _publishers) {
+    _killed.add(name)
     proc.kill()
     hostLog(`mDNS: unpublished ${toSubdomain(name)}.${LOCAL_HOST}`)
   }
   _publishers.clear()
 }
+
+function republish(name: string) {
+  const attempts = _republishAttempts.get(name) ?? 0
+  const delay = Math.min(REPUBLISH_BASE_DELAY * 2 ** attempts, MAX_REPUBLISH_DELAY)
+  _republishAttempts.set(name, attempts + 1)
+
+  hostLog(`mDNS: ${toSubdomain(name)}.${LOCAL_HOST} exited unexpectedly, retrying in ${delay}ms`)
+  setTimeout(() => publishApp(name), delay)
+}