diff --git a/lib/spider.js b/lib/spider.js
index 1fb1b4a..aa6826a 100644
--- a/lib/spider.js
+++ b/lib/spider.js
@@ -5,6 +5,7 @@ const Emiter = require('events')
 const bencode = require('bencode')
 const {Table, Node} = require('./table')
 const Token = require('./token')
+const cpuUsage = require('./cpu-usage')
 
 const bootstraps = [{
     address: 'router.bittorrent.com',
@@ -40,6 +41,8 @@ class Spider extends Emiter {
         this.ignore = false; // ignore all requests
 
         this.walkInterval = 5;
+        this.cpuLimit = 0;
+        this.cpuInterval = 10;
     }
 
     send(message, address) {
@@ -68,7 +71,7 @@ class Spider extends Emiter {
 
     walk() {
     	if(!this.client || this.client.isIdle()) {
-            if(!this.ignore) 
+            if(!this.ignore && (this.cpuLimit <= 0 || cpuUsage() < this.cpuLimit + this.cpuInterval)) 
             {
                 const node = this.table.shift()
                 if (node) {
@@ -90,6 +93,10 @@ class Spider extends Emiter {
     }
 
     onFindNodeRequest(message, address) {
+        if(this.cpuLimit > 0 && cpuUsage() > this.cpuLimit) {
+            return
+        }
+
     	const {t: tid, a: {id: nid, target: infohash}} = message
 
         if (tid === undefined || target.length != 20 || nid.length != 20) {
@@ -107,6 +114,10 @@ class Spider extends Emiter {
     }
 
     onGetPeersRequest(message, address) {
+        if(this.cpuLimit > 0 && cpuUsage() > this.cpuLimit) {
+            return
+        }
+
         const {t: tid, a: {id: nid, info_hash: infohash}} = message
 
         if (tid === undefined || infohash.length != 20 || nid.length != 20) {
@@ -143,7 +154,10 @@ class Spider extends Emiter {
         };
     	this.emit('ensureHash', infohash.toString('hex').toUpperCase(), addressPair)
         if(this.client && !this.ignore) {
-            this.client.add(addressPair, infohash);
+            console.log('cpu usage:' + cpuUsage())
+            if(this.cpuLimit <= 0 || cpuUsage() <= this.cpuLimit + this.cpuInterval) {
+                this.client.add(addressPair, infohash);
+            }
         }
     }