async-log

Utility and sample code for logging async operations in the context of a web-server using the async_hooks core api

Requirements

• node: > 8.1.0

Use the helper

(you can view the demo.js file for all the details)

• add it as a dependency

  yarn add async-log,

• include it in your main entry point

  const asyncLog = require('async-log');

• create a transaction every time your server handles a request

  const trans = asyncLog.newTransaction({
   url: req.url,
  });
  

• end the transaction every time your server finished handling the request

  trans.end();
  

• in between these two calls, every time you want to track fetching a remote resource you need to create a new trace before, then end the created trace after

  const trace = asyncLog.newTrace({ type: 'db' });
  //...
  trace.end();
  

Use the demo

• clone this repo and change directory to it's folder

• start the server in one tab

  node demo.js

• make request to the server in another tab

  curl http://localhost:3131/ & curl http://localhost:3131/yoyo & wait
  

• in the initial tab, you will see how much each request took, and out of that how much it waited for async resources (file access, network requests, etc.)

Caveats

• the async wait measurements also include some overhead. So it's not 100% accurate. I consider it close enough for my needs.

Acknowledgements

This is inspired by this talk from Thomas Watson and his example code