Introduction to Node.js at the GfK Nurago and SirValUse Academy 2013

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Overview

This is an Introduction to Node.js given at the GfK Nurago and SirValUse Academy 2013 in Hamburg. In this talk I try to reason about the use of server-side JavaScript and try to workout what makes Node.js so special – The Event Loop.
At the end of the talk I give some examples of which I think are particular good  use cases for Node.js. I also make some notes about running Node in a productive environment.

For notes

Notes

Slide # 1

1. Introduce Yourself 😉
   1. Henning Kropp @ GfK Nurago
2. Who has NOT heard of Node.js before?
   1. Node.js is 5 years old
   2. Node.js hottest tech topic:
      1. We want to find out WHY?

Slide #2

1. Aim of the Talk:
   1. Motivate the Use of JavaScript
   2. Introduce Node.js
   3. Explain Event Driven / Event Loop
   4. Show Sample Use Cases
   5. Some Notes about Production Node

Slide #3

• What Do This Companies Have in Common?

Slide #4

• (Among Other Things ….) => JavaScript
• Remember the Browser Wars?
• Race for Fastest Runtime Environment / VM
• Other Platforms:
  • Microsoft -> .Net
  • Oracle -> Java/JVM
  • Apple -> ObjectC
  • Google -> Go and other???
• Nashorn Part of JDK8 (maybe)
• Chakra Part of Windows 8 and Windows RT

Slide #5

• Dozens of Platforms Support JavaScript!
• At Nurago:
  • Client a Lot of JavaScript
  • Mobile a Lot of JavaScript
  • Web Pages a Lot of JavaScript
  • …. Server Not so Much… 😦

Slide #6

• Last but not Least:
  • Hundreds of Thousands of Websites Developed in JS
  • Thousands of JS Developers

Slide #7

• Key Facts:
  • JavaScript Most Popular Language
  • Used and Backed by Key IT Companies
  • Thousands of Developers
  • Resources & Ecosystem
  • A lot of Money and Man Years
  • One Language Client/Server
• Douglas Crockford responsible for maturity
  • JS the Good Parts the Only Book One should Read
  • JSLint for Static Code Analysis

Slide #8

• Few know JavaScript Part of Server since Beginning
  • Netscape Enterprise Server 1994
  • Also IIS in 90s
• Since 2008 CommJS specification for not Browser
  • Server-side JavaScript applications
  • Command line tools
  • Desktop GUI-based applications
  • Hybrid applications (Titanium, Adobe AIR)
• RingoJS -> Java Based
• Don’t Know Much About Jetpack
• AND NODE.JS

Slide #9

• Why Node?
  • Event Driven
  • Non-Blocking
  • Single Threaded!
  • Networking!
• Need to Understand Modern Web requirements
• Need to Understand Non-Blocking
• Need to Understand Event Driven
• But Before that Have Some Look at Some Code

• Examples! Code!

Slide #10

• Node.js is Essentially About Networking!
• createServer() Does not Block
• Non-blocking thru Callbacks
• Callbacks, Functions First-Class Citizens in JS
  • One of the Good Parts
• Running Apache Benchmark
  • Able to Scale the Webserver on Laptop to 900 Concurrent
• Next: What Does Single Threaded Mean?

Slide #11

• Node.js is Single Threaded!
• How Does this Scale on my Laptop?
• Trying 10 con. Requests.
• What Time Do You Expect?
• Node is Blocking/Single Threaded
• Node API is Not Blocking
• File Read/Write … I/O
• Node Uses the Event Loop
• Next Simple REST

Slide #12

• Simple Example of REST
• Why Would We Need a Networking Framework?
• Why Event Driven?
• Have to Look at Modern Web Requirements!

Slide #13

• This is The Classic Web
• Process by Order
• Apache Spawns Process/Thread for Every Request

Slide #14

• Today Web is a Eventful Web
• User Want Imitate Responses
• Small but many Requests
• For example:
  • Instant Search at Google
  • Every Search at Google with Auto Completion Results in Multiple Requests
• User Expects this Behaviour

Slide #15

• Who Ever Had the Pleasure of Scaling a Web App Probably used NginX
• NginX and Node.js -> Event Driven!
• NEXT: Lets have a look at the Event Loop!

Slide #16

• Events are put on the Event Loop
  • Like ‘onRequest‘
  • One/Many Callbacks per Event
  • A Thread waiting for Request
  • If Requests Occurs, Callback is Run
  • Than Response is Send to Client
• Everything (I/O) is Asynchronous
  • File reads
  • Database Access
• Callback Function is Used
• HOW IS DIFF FROM TRADITIONAL WEBSERVER?

Slide #17

• Event Loop @ a McDonalds
• Imagine Ur at the Counter Placing an Order
• Process/Thread = Cashier
• Cashier Taking Order and Waits for Burger and Fries
• One Process for one Order
• Only after Assemble Order finished -> Next Order/Customer
• Most the Time Waiting for Burger and Fries
• Apache Basically Works that Way

Slide #18

• While We wait for Burger People line Up
• All have to wait till Cashier is finished w/ One Order
• Who can We Scale This?

Slide #19

• We could Create hire more Processes
  • Can get crowded behind the Counter
  • Still Most of the Time Waiting
  • What the Apache is Doing
• How Does McD Scale This, If a Order Takes Longer Than Certain Time?
  • You get a Number!
  • That’s Event Driven
  • When the Burger is Ready Process Stops What he was Doing and Serves the Burger
  • Process Does Not Wait

Slide #20

• Node is Useful for I/O!
• Network, Files, Databases …
• File Server for Example
• What of This Code is Async?
• What of This Code is Blocking?
• Where is the Event Loop Here?

Slide #21

• Node.js as a Proxy
• Most Popular Proxy Module is http-proxy
• nodejitsu.com Uses http-proxy
• Not very Readable Example, Lets Skip Details 😉

Slide #22

• Screen scrpaing – JavaScript End-to-End
• Jsdom is Slow, Often Used PhantomJS

Slide #23

• Forever Restarts, and Detaches From Shell
• Cluster creates Worker for each CPU Core
  • One Node Server/Thread per CPU Core
  • Example later
• Cloud support with Windows Azure and nodjitsu and many more
• Node Production Environment Does Some Optimizations
  • Caching
  • And Others

Slide #24

• Example of Cluster Usage
• All Workers Run on Same Port