Optimize Idle CPU/Dash

server/core/peer-registry.js

@@ -9,20 +9,54 @@ export class PeerRegistry {
   constructor() {
     /** @type {Map<string, import('../rpc/session.js').PeerSession>} */
     this.sessions = new Map()
+    /** @type {Set<(size: number, prevSize: number) => void>} */
+    this._listeners = new Set()
+  }
+
+  /**
+   * Subscribe to peer count changes (add / remove / clear).
+   * @param {(size: number, prevSize: number) => void} fn
+   * @returns {() => void} unsubscribe
+   */
+  onChange(fn) {
+    if (typeof fn !== 'function') return () => {}
+    this._listeners.add(fn)
+    return () => {
+      this._listeners.delete(fn)
+    }
+  }
+
+  /**
+   * @param {number} prevSize
+   */
+  _emitChange(prevSize) {
+    const size = this.sessions.size
+    if (size === prevSize) return
+    for (const fn of this._listeners) {
+      try {
+        fn(size, prevSize)
+      } catch (err) {
+        log.debug('onChange listener failed', { error: err?.message })
+      }
+    }
   }
 
   /**
    * @param {import('../rpc/session.js').PeerSession} session
    */
   add(session) {
+    const prev = this.sessions.size
     this.sessions.set(session.id, session)
+    this._emitChange(prev)
   }
 
   /**
    * @param {string} id
    */
   remove(id) {
-    this.sessions.delete(id)
+    const prev = this.sessions.size
+    const had = this.sessions.delete(id)
+    if (had) this._emitChange(prev)
   }
 
   /**
@@ -46,6 +80,7 @@ export class PeerRegistry {
    * @param {unknown} payload
    */
   broadcast(method, payload) {
+    if (this.sessions.size === 0) return
     for (const session of this.sessions.values()) {
       try {
         session.push(method, payload)
@@ -60,6 +95,7 @@ export class PeerRegistry {
   }
 
   clear() {
+    const prev = this.sessions.size
     for (const session of this.sessions.values()) {
       try {
         session.destroy()
@@ -68,6 +104,7 @@ export class PeerRegistry {
       }
     }
     this.sessions.clear()
+    this._emitChange(prev)
   }
 }