dustjs: how to profile and/or time rendering?

Question

I'm debugging some dustjs template render sluggishness after calling res.render from an express controller. There are a few (fast) async calls from dust helpers, but even when they're removed I'm occasionally seeing templates take multiple seconds to render, which is surprising since they're all pre-compiled.

Is there any built in timing/logging for dustjs or do I just need to profile the entire application?

Answer 1

You can add some simple profiling in Node by monkey-patching dust.render like this:

var dust = require('dustjs-linkedin');
var render = dust.render;
dust.render = function(name, context, callback) {
  var timeStart = process.hrtime();
  render(name, context, function() {
    var timeDiff = process.hrtime(timeStart);
    console.log(name, timeDiff[0] * 1000 + timeDiff[1] / 1000000);
    callback.apply(undefined, arguments);
  });
};

When you run your application, look at the console to see how much time rendering takes. Rendering a normal Dust template takes on the order of milliseconds.

> node app.js

hello 0.832608
Hello world! Using Dust version 2.7.1!

This template took 0.8ms to render.