dump.js

var heapdump = require('heapdump');
var lastHeapUsed;

setTimeout(function() {
  dump(process.memoryUsage().heapUsed);

  setInterval(function() {
  	var heapUsed = process.memoryUsage().heapUsed;
  	if (heapUsed > 2*lastHeapUsed)
  	  dump(heapUsed);
  }, 5000);
}, 1);

function dump(heapUsed) {
	heapdump.writeSnapshot(process.pid + '-' + (heapUsed >> 20) + '.heapsnapshot');
    lastHeapUsed = heapUsed;
}