Event-Collector

Allows you to collect meta-data and time different phases in the context of one bigger event.

Install

The usual npm install event-collector --save or yarn add event-collector

Creating an EventCollector

With Express

If you are using Express the easiest way to get started is with:

const express = require('express');
const EventCollector = require('event-collector');

const app = express();
app.use(EventCollector.express({some: 'fixed metadata'}, (eventcollector) => {
  console.log(JSON.stringify(eventcollector, null, 2));
}));

This will create a new EventCollector at request.eventcontroller with fixed metadata that will be added to every event. Use this for things like hostnames, versions of your software etc. Use that to add meta-data and time jobs. It will automatically call end add the following metadata:

• request.hostname
• request.url
• request.method
• response.statusCode
• response.getHeader('content-type)
• response.getHeader('content-encoding
• response.getHeader('cache-control)

The callback passed into the constructor will be called when the request is finished and you can do something useful with all the information you just collected, like logging it, or sending it to 3rd parties like http://honeycomb.io

Without Express

If you are not running Express you can easily create your own EventCollector with const eventcollector = new EventCollector();

Usage

addMeta(meta)

Adds all the keys in meta to the existing meta-data. If one or more keys in meta were already present they will be overwritten.

addError(error)

Adds the error to the errors array and increase errorCount by 1.

startJob(type, meta)

Starts timing a new job with type. If a job already exists with that type a dash + counter is added. Optionally you can pass in meta, which will be added to this particular job. This method saves how many milliseconds into the event we are when the job is started. This is stored as startAtMs. Returns the id of the job.

endJob(id, meta)

Ends the job with the id and stores the duration of this particular job. Optionally you can pass in some meta to be added to the job.

end(meta)

Ends the event and store the totalDuration

Example output

{
  "meta": {
    "hostname": "localhost",
    "url": "/cafes/opal-cafe",
    "method": "GET",
    "rendererVersion": "3.4.2",
    "renderProfile": "linc-profile-generic-react-redux-routerv3",
    "statusCode": 200,
    "contentType": "text/html",
    "contentEncoding": "gzip"
  },
  "time": 1494585065359,
  "jobs": {
    "rendering": {
      "startAtMs": 3.007,
      "durationInMs": 1069.266
    },
    "match": {
      "startAtMs": 3.315,
      "durationInMs": 9.811
    },
    "writeInitialHead": {
      "startAtMs": 13.317,
      "durationInMs": 10.305
    },
    "firstFlush": {
      "startAtMs": 23.147,
      "durationInMs": 0.259
    },
    "firstRenderPass": {
      "startAtMs": 23.819,
      "durationInMs": 44.122
    },
    "rendererInitialSetup": {
      "startAtMs": 23.847,
      "durationInMs": 2.825
    },
    "firstRender": {
      "startAtMs": 26.694,
      "durationInMs": 41.21
    },
    "secondRenderPass": {
      "startAtMs": 1063.935,
      "durationInMs": 6.895
    },
    "sendMainContent": {
      "startAtMs": 1070.966,
      "durationInMs": 1.322
    }
  },
  "errs": [],
  "errorCount": 0,
  "totalDuration": 1074.686
}