Fix #277

changelog

@@ -1,3 +1,10 @@
+Fri Sep  6 15:51 2013 CDT
+    * lib/utilities.js: Tweak the throttle code for rate limiters to fix
+      incorrect behavior of the burst cap after the cooldown period has
+      been passed
+    * tests/rateLimiter.js: Write a couple quick test cases to ensure that
+      rate limiting is handled properly
+
 Thu Sep  5 22:52 2013 CDT
     * www/assets/js/callbacks.js: Disable the channel registration button
       and change its text while a registration attempt is being processed

lib/utilities.js

@@ -76,16 +76,16 @@ module.exports = {
                 if (isNaN(cooldown))
                     cooldown = burst / sustained;
 
-                // Haven't reached burst cap yet, allow
+                // Cooled down, allow and clear buffer
-                if (this.count < burst) {
+                if (this.lastTime < Date.now() - cooldown*1000) {
-                    this.count++;
+                    this.count = 1;
                     this.lastTime = Date.now();
                     return false;
                 }
 
-                // Cooled down, allow and clear buffer
+                // Haven't reached burst cap yet, allow
-                if (this.lastTime < Date.now() - cooldown*1000) {
+                if (this.count < burst) {
-                    this.count = 0;
+                    this.count++;
                     this.lastTime = Date.now();
                     return false;
                 }

tests/rateLimiter.js

@@ -0,0 +1,52 @@
+var $util = require('../lib/utilities.js');
+
+function testBurst() {
+    var lim = $util.newRateLimiter();
+    var params = {
+        burst: 10,
+        sustained: 2
+    };
+
+    for (var i = 0; i < 10; i++) {
+        if (lim.throttle(params)) {
+            console.log("[FAIL] Burst: Unexpected throttle");
+            return;
+        }
+    }
+
+    if (!lim.throttle(params)) {
+        console.log("[FAIL] Burst: didn't throttle after exceeding burst amount");
+        return;
+    }
+
+    console.log("[PASS] Burst");
+}
+
+function testBurstAndWait() {
+    var lim = $util.newRateLimiter();
+    var params = {
+        burst: 10,
+        sustained: 2
+    };
+
+    for (var i = 0; i < 9; i++) {
+        if (lim.throttle(params)) {
+            console.log("[FAIL] Burst & Wait: Unexpected throttle");
+            return;
+        }
+    }
+
+    // Wait a while and try some more
+    setTimeout(function () {
+        for (var i = 9; i < 17; i++) {
+            if (lim.throttle(params)) {
+                console.log("[FAIL] Burst & Wait: Unexpected throttle");
+                return;
+            }
+        }
+        console.log("[PASS] Burst & Wait");
+    }, 6000);
+}
+
+testBurst();
+testBurstAndWait();