Count expected number of arrivals and stop the timer when reached

Stop the timer when the expected number of arrivals is reached rather
than with another timeout.

This is to avoid triggering a Node.js bug that leads to using
100% CPU.

Ref: nodejs/node#9756

lib/index.js

@@ -3,6 +3,7 @@
 var EventEmitter = require('events').EventEmitter;
 var util = require('util');
 var Nanotimer = require('nanotimer');
+var debug = require('debug')('arrivals');
 
 module.exports = {
   uniform: {
@@ -23,7 +24,9 @@ function createPoisson(mean, duration) {
 }
 
 function UniformProcess(tickInterval, duration) {
-  this._tickInterval = tickInterval;
+  debug(`tickInterval = ${tickInterval}, duration = ${duration}`);
+  this._tickInterval = Math.floor(tickInterval);
+  debug(`this._tickInterval set to ${this._tickInterval}`);
   this._interval = null;
   this._duration = duration || null; // ms
   this._timer = new Nanotimer();
@@ -34,14 +37,20 @@ util.inherits(UniformProcess, EventEmitter);
 
 UniformProcess.prototype.start = function() {
   var self = this;
+  var arrivals = 0;
+  var maxArrivals = Infinity;
+  if (self._duration) {
+    maxArrivals = Math.floor(self._duration / self._tickInterval);
+  }
+  debug(`maxArrivals = ${maxArrivals}`);
   self._interval = self._timer.setInterval(function() {
     self.emit('arrival');
-  }, '', self._tickInterval + 'm');
-  if (self._duration) {
-    self._timer.setTimeout(function() {
+    arrivals++;
+    if (arrivals === maxArrivals) {
+      debug(`maxArrivals reached, stopping`);
       self.stop();
-    }, '', (self._duration + self._tickInterval / 2) + 'm');
-  }
+    }
+  }, '', self._tickInterval + 'm');
   return self;
 };
 

package.json

@@ -21,6 +21,7 @@
   "author": "Hassy Veldstra <h@artillery.io>",
   "license": "ISC",
   "dependencies": {
+    "debug": "2.3.3",
     "nanotimer": "0.3.14"
   },
   "devDependencies": {

test/index.js

@@ -53,7 +53,7 @@ tape('Can create a uniform process', function(t) {
   t.ok(true, 'Process started');
   setTimeout(function() {
     p.stop();
-    t.assert(count === 6, 'Correct number of arrivals');
+    t.assert(count === 6, `Correct number of arrivals - got ${count} - 1`);
     t.end();
   }, 2700);
 });
@@ -66,7 +66,7 @@ tape('Can create a uniform process with fixed duration', function(t) {
   });
   p.once('finished', function() {
     t.ok(true, '  got finished event');
-    t.assert(count === 7, 'Correct number of arrivals');
+    t.assert(count === 6, `Correct number of arrivals - got ${count} - 2`);
     t.end();
   });
 
@@ -84,7 +84,8 @@ tape('Expect number of arrival events get emitted', function(t) {
     count++;
   });
   p.once('finished', function () {
-    t.assert(count === arrivalCount, 'Got the expect number of arrivals');
+    console.log(`count = ${count}, arrivalCount = ${arrivalCount}`);
+    t.assert(count === arrivalCount, 'Got expected number of arrivals');
     t.end();
   });
   p.start();