Understand How Node.js and Core Features Works and You dont know Node.JS

1. You Don’t know Node.js®
Quick Intro to Core Features

2. Hengki Sihombing
Co-Founder & CTO at Urbanhire

3. Agenda
• Why use Node.JS
• How it’s work
• Quick Intro Core Features Node
• Node.js at Urbanhire
• Q & A

4. Slides & Code
Everything: hBps://github.com/aredo/Ha-pdc-2017
or
Just pdf Slides

5. What the Hell Node.js is
• JavaScript runHme built on Chrome's V8 JavaScript
engine.
• an event-driven
• Asynchronous (libuv)
• Single Threaded but highly Scalable
• Non Buffering

6. StarHng with basics:
Why Use Node.js®

7. Why Node.js
• Speed Development
• EffecHve single codebase
• It is a good fit for real-Hme applicaHons
• Node.js app will take up less system RAM
• Because is Asynchronous

8. Input/output is one of the
most expensive
type tasks (>CPU)

9. The cost of I/O ?
• Accessing RAM ~ 250 CPU cycle
• Disk OperaHons ~ 41 000 000 CPU cycle
- Read a file
- Write a File
• Network I/O ~ 240 000 000 CPU cycles
- Database Query responses
- HBp responses
- Memcache results
hBps://goo.gl/aU4TfP

10. Node has
non-blocking I/O

11. PHP Sleep Node.js Sleep

12. So…,
How Node.js
works?

13. Blocking Web Server

15. Non-Blocking Web
Server

17. Most web applicanHon are I/O
Bound not CPU Bound

18. hBps://www.slideshare.net/marcusf/nonblocking-io-event-loops-and-nodejs

19. hBps://help.dreamhost.com/hc/en-us/arHcles/215945987-Web-server-performance-comparison

20. Blocking systems have to
be mulH-threaded

21. Thread per connecHon
is Expensive

22. [MulH-threading] is the soWware
equivalent of a nuclear device because
if it is used incorrectly, it can blow up
in your face.
hBps://blog.codinghorror.com/threading-concurrency-and-the-most-powerful-psychokineHc-explosive-in-the-univ

23. Node is single threaded…
and that's good!

24. Event Loop

25. JavaScript has a concurrency model
based on an "event loop". This
model is quite different from models
in other languages like C and Java.

26. How exactly Event Loop
works?

28. Bert Belder
Libuv & Node.js Core developer
hBps://www.youtube.com/watch?v=PNa9OMajw9w

29. h_ps://goo.gl/aiT9Ga

30. hBps://www.youtube.com/watch?v=PNa9OMajw9w

31. hBps://www.youtube.com/watch?v=PNa9OMajw9w

32. hBps://www.youtube.com/watch?v=PNa9OMajw9w

33. hBps://www.youtube.com/watch?v=PNa9OMajw9w

34. hBps://www.youtube.com/watch?v=PNa9OMajw9w

35. Entering Node.js
• Single thread for your code
• … but I/O run in parallel
• Handle thousand of concurrent with single connecHon
• Need to be careful with CPU-intensive code

36. But..,
It's sHll possible
to write
blocking code in
Node.js

37. Blocking Node.js Code

38. Blocking Node.js Code

39. Non-Blocking Node.js Code

40. Most of Node.js is JavaScript

41. Node.js !== Browser JavaScript

42. global || GLOBAL
How to create global variables
(no window in Node.js) ???

43. global has properHes

44. global.__filename
global.__dirname
global.module
global.require()

45. global.process or process

46. with process, you can do…!!
• Access CLI input?
• Get system info: OS, plaoorm, memory usage,
versions, etc.?
• Read env vars (passwords!)?

47. process.env
process.argv
process.pid
process.cwd()
process.exit()
process.kill()
hBps://nodejs.org/api/process.html

48. Who likes and
understands
callbacks?

49. callbackhell.com

51. Handling Callback Hell
• Async.js
• Promises (NaHve, Bluebird, Q)
• Generatos / co module
• async/wait (Node v7 and v8)

52. How to handle
async errors?

53. Handling Async Errors
• Event Loop: Async errors are harder to handle/debug,
because system loses context of the error. Then,
applicaHon crashes.
• Try/catch is not good enough, but for sync errors try/
catch works fine

54. Best PracHces for Async Errors?
• Listen to all “on error” events
• Listen to uncaughtExcepHon
• Use domain (sos deprecated) or AsyncWrap
• Log, log, log & Trace
• NoHfy (opHonal)
• Exit & Restart the process

55. on(‘error’)
Anything that inherits from or creates an instance of the
above: Express, LoopBack, Sails, Hapi, etc.

56. uncaughtExcepHon
uncaughtExcepHon is a very crude mechanism for excepHon
handling. An unhandled excepHon means your applicaHon - and
by extension Node.js itself - is in an undefined state. Blindly
resuming means anything could happen.

57. How to deal with uncaughtExcepHon
• You applicaHon shouldn’t have uncaughtexcepHons. This is clearly insane.
• You should let your applicaHon crash, find uncaught excepHons and fix them.
This is clearly insane.
• You should swallow errors silently. This is what lots of people do and it is bad.
• You should let your applicaHon crash, log errors and restart your process with
something like pm2, forever, upstart or monit. This is pragmaHc.
• TesHng… TesHng.. TesHng...

58. uncaughtExcepHon Examples

59. Events
Events are part of core and supported by most of
the core modules while more advanced paBerns
such as promises, generators, async/await are
not.

60. Events == Node Observer Pa_ern
• Subject
• Observers (event listeners) on a subject
• Event triggers

61. Events in Node.js

62. Events in Node.js

63. Listeners

64. Problems with Large Data
• Speed: Too slow because has to load all
• Buffer limit: ~1Gb
• Overhyped

65. • Every acHon on a computer is an event. Like when
a connecHon is made or a file is opened
• In node.js an event can be described simply as a
string with a corresponding callback.

66. Stream
AbstracHons for conHnuous
chunking of data
a stream is a sequence of data elements made available over Hme.
hBps://en.wikipedia.org/wiki/Stream_(compuHng)

67. No need to wait for
the enHre resource to load

68. Streams Inherit from
Event Emi_er

69. Streams are Everywhere!
• HTTP requests and responses
• Standard input/output (stdin&stdout)
• File reads and writes

70. List naHve Node.js objects implement the
streaming interface

71. Read & Write Steam

72. Streams and Buffer Demo

73. Results

74. Streams Resources
Stream automated workshop: hBps://github.com/substack/
stream-adventure
$ sudo npm install -g stream-adventure
$ stream-adventure
hBps://github.com/substack/stream-handbook

75. How to scale a single
threaded system?

76. Cluster Usage
• Master: starts workers
• Worker: do the job, e.g., HTTP server
• Number of processes = number of CPUs

77. Cluster

78. pm2
hBps://github.com/Unitech/pm2
hBp://pm2.keymetrics.io
Advantages:
• Load-balancer and other features
• 0s reload down-Hme, i.e., forever alive
• Good test coverage

79. Node.js at Urbanhire

80. 99.5% Urbanhire code
write with Node.js

81. Use Case
• Express REST API (Microservices)
• Scraping engine
• RealHme NoHficaHon
• Streaming data from MongoDB to ElasHcserch
• Queue message with NSQ
• Cronjob

82. One Last Thing

83. Atwood’s Law
Any applicaHon that can be
wriBen in JavaScript,
will eventually be writen in
JavaScript
Codinghorror.com

84. Thank You
Be a part our Team
hBps://www.urbanhire.com/careers