fix(script): memory leak and performance improvement

There is a bug in node with vm.runInNewContext: nodejs/node-v0.x-archive#6552
This was used for every script call by deployd, and for example GET scripts are being run for every record returned -> so if you need to return 1000 records, the scripts would run 1000 times resulting in big memory leaks.

With this change, even 15000 executions of a script take now just 300 ms on my machine and use virtually no extra memory, compared to huge memory leaks and over several minutes with the old code.

lib/script.js

@@ -9,12 +9,34 @@ var vm = require('vm')
 
 function Script(src, path) {
   try {
-    this.compiled = vm.createScript('(function() {' + src + '\n}).call(_this)', path);
+    this.src = src;
+    this.path = path;
   } catch(ex) {
     this.error = ex;
   }
 }
 
+Script.prototype.runInSandbox = function (sandbox) {
+  var functionArgs = Object.keys(sandbox);
+
+  // remove the argument 'this' from our list of passed argument, because it is a reserved word
+  functionArgs.splice(functionArgs.indexOf('this'), 1);
+
+  var script = '(function (' + functionArgs.join(',') + ') { return (function() {' + this.src + '\n}).call(_this); })';
+  var func = vm.runInThisContext(script, this.path);
+
+  // pass our arguments from the sandbox to the function
+  var args = [];
+  functionArgs.forEach(function (p) {
+    if (p === '_this' && !sandbox[p]) {
+      args.push({});
+    } else {
+      args.push(sandbox[p]);
+    }
+  });
+  return func.apply(null, args);
+};
+
 /**
  * Run the current script in the given sandbox. An optional domain may be provided to extend the sandbox exposed to the script.
  */
@@ -112,7 +134,7 @@ Script.prototype.run = function (ctx, domain, fn) {
   var err;
 
   try {
-    this.compiled.runInNewContext(scriptContext);
+    this.runInSandbox(scriptContext);
   } catch(e) {
     err = wrapError(e);
     scriptContext._error = err;

test/script.unit.js

@@ -29,6 +29,20 @@ describe('script', function(){
       var s = new Script('if(!foo) throw "foo not passed"');
       s.run({}, {foo: 123}, done);
     });
+
+    it('should not be slow and leak memory', function (done) {
+      var s = new Script('if(!foo) throw "foo not passed"');
+      var time = Date.now();
+      var numDone = 0;
+      for (var i = 0; i < 15000; i++) {
+        s.run({ }, { foo: 123 }, function() {
+          numDone++;
+          if (numDone >= 15000) {
+            done();
+          }
+        });
+      }
+    });
   });
 
   describe('async', function(){