Custom Artillery functions to print the latency distribution for a single HTTP request

processor.js

//
// Custom Artillery functions to print the latency distribution for a single HTTP request
//
// Example usage: (in your scenario)
// - get:
//     url: "/some/endpoint"
//     beforeRequest: ["recordStartTime"]
//     afterResponse: ["logLatencyDelta"]
//     name: "Optional name for the endpoint for the report"

module.exports = {
  recordStartTime: recordStartTime,
  logLatencyDelta: logLatencyDelta
};

/**
 * Pre-request hook to set requestLatency variable to current time
 */
function recordStartTime(req, ctx, events, done) {
  ctx.vars['requestLatency'] = Date.now();
  return done();
}

/**
 * Post-response hook to calculate and log how long the request took
 */
function logLatencyDelta(req, res, ctx, events, done) {
  if (!ctx.vars.requestLatency) {
    return done();
  }

  let delta = Date.now() - ctx.vars['requestLatency'];
  events.emit('customStat', { stat: req.name + ' latency', value: delta });
  return done();
}