1.
Nodejs
Event-Driven concurrency for Web
Applications
Ganesh Iyer
@lastlegion
http://ganeshiyer.net

2.
What is Node
Server-side JavaScript runtime
http://ganeshiyer.net

3.
What is Node
Server-side JavaScript runtime
http://ganeshiyer.net

4.
What is Node
Server-side JavaScript runtime
Built on Google’s V8 Engine
http://ganeshiyer.net

5.
What is Node
Server-side JavaScript runtime
Built on Google’s V8 Engine
http://ganeshiyer.net

6.
What is Node
Server-side JavaScript runtime
Built on Google’s V8 Engine
Why another server side technology?
http://ganeshiyer.net

7.
What is Node
Server-side JavaScript runtime
Built on Google’s V8 Engine
Why another server side technology?
http://ganeshiyer.net

8.
What is Node
Server-side JavaScript runtime
Built on Google’s V8 Engine
Why another server side technology?
http://ganeshiyer.net

9.
What is Node
Server-side JavaScript runtime
Built on Google’s V8 Engine
Why another server side technology?
http://ganeshiyer.net

10.
What is Node
Server-side JavaScript runtime
Built on Google’s V8 Engine
Uses an event-driven, non-blocking I/O model
for building scalable network applications
http://ganeshiyer.net

11.
What is Node
Server-side JavaScript runtime
Built on Google’s V8 Engine
Uses an event-driven, non-blocking I/O model
for building scalable network applications
http://ganeshiyer.net

12.
What is Node
Server-side JavaScript runtime
Built on Google’s V8 Engine
Uses an event-driven, non-blocking I/O model
for building scalable network applications
http://ganeshiyer.net

13.
What is Node
Server-side JavaScript runtime
Built on Google’s V8 Engine
Uses an event-driven, non-blocking I/O model
for building scalable network applications
http://ganeshiyer.net

14.
Concurrency in web
servers
http://ganeshiyer.net

15.
Two main approaches
• Threads
• Events
http://ganeshiyer.net

16.
Thread Based
• Creates a new thread( or process) for handling
a new connection.
http://ganeshiyer.net

17.
Thread Based
• Creates a new thread( or process) for handling
a new connection.
Server Process
http://ganeshiyer.net

18.
Thread Based
• Creates a new thread( or process) for handling
a new connection.
New
Connection
Server Process
http://ganeshiyer.net

19.
Thread Based
• Creates a new thread( or process) for handling
a new connection.
Request
handler
Process
New
Connection
Server Process
http://ganeshiyer.net

20.
Thread Based
• Creates a new thread( or process) for handling
a new connection.
Request
handler
Process
Server Process
http://ganeshiyer.net

21.
Thread Based
• Creates a new thread( or process) for handling
a new connection.
Request
handler
Process
Server Process
http://ganeshiyer.net

22.
Threads used in Apache(MPM)
Prefork
http://ganeshiyer.net

23.
Threads used in Apache(MPM)
Worker
http://ganeshiyer.net

24.
Scalability Issues
There is a maximum number of threads(T’) that a
system can support, beyond which the
throughput decreases.
http://ganeshiyer.net

25.
Scalability Issues
Source: M. Welsh, S. D. Gribble, E. A. Brewer, and D. Culler. A design framework for highly con-current systems. Technical Report
UCB/CSD-00-1108, U.C. Berkeley Computer Science Division, April 2000.
http://ganeshiyer.net

26.
Scalability Issues
Under heavy load a multi-threaded web
server consumers large amounts of memory
http://ganeshiyer.net

27.
Scalability Issues
Under heavy load a multi-threaded web
server consumers large amounts of memory
Single thread stack for each connection
http://ganeshiyer.net

28.
Scalability Issues
Under heavy load a multi-threaded web
server consumers large amounts of memory
Single thread stack for each connection
Overhead due to context-switching and
scheduling increases drastically with large
number of threads
http://ganeshiyer.net

29.
Event Based
http://ganeshiyer.net

30.
Event Based
States
Event Event Handler
Loop
Event Queue
http://ganeshiyer.net

31.
Event Based
Event Emitters
States
Event Event Handler
Loop
Event Queue
http://ganeshiyer.net

32.
Event Based
Event Emitters
States
Event Event Handler
Loop
Event Queue
http://ganeshiyer.net

33.
Event Based
Use an event loop
http://ganeshiyer.net

34.
Event Based
Use an event loop
Multiple connections are mapped to a single
thread.
http://ganeshiyer.net

35.
Event Based
Use an event loop
Multiple connections are mapped to a single
thread.
This Thread handles all occurring events from
I/O operations of these connections and
requests.
http://ganeshiyer.net

36.
Improved scalability
Source: M. Welsh, S. D. Gribble, E. A. Brewer, and D. Culler. A design framework for highly con-current systems. Technical Report
UCB/CSD-00-1108, U.C. Berkeley Computer Science Division, April 2000.
http://ganeshiyer.net

37.
Improved scalability
The event loop has a queue of event handlers
that it executes in order.
The overhead when switching from one event
handler to the next time is much lower.
http://ganeshiyer.net

38.
Nodejs
http://ganeshiyer.net

39.
Why Server-side JavaScript?
Unified language for both front end an backend
http://ganeshiyer.net

40.
Why Server-side JavaScript?
Unified language for both front end an backend
Increased programmer productivity
http://ganeshiyer.net

41.
Why Server-side JavaScript?
Unified language for both front end an backend
Increased programmer productivity
Code reuse
http://ganeshiyer.net

42.
Why Server-side JavaScript?
Unified language for both front end an backend
Increased programmer productivity
Code reuse
exchange of data using JSON
http://ganeshiyer.net

43.
Why Server-side JavaScript?
Unified language for both front end an backend
Increased programmer productivity
Code reuse
exchange of data using JSON
Speed!
http://ganeshiyer.net

44.
Why Server-side JavaScript?
Unified language for both front end an backend
Increased programmer productivity
Code reuse
exchange of data using JSON
Speed! Contrary to popular belief, Javascript
with the V8 engine performs is faster than
PHP, Ruby and Python
http://ganeshiyer.net

45.
Nodejs Architecture
http://ganeshiyer.net

46.
Architecture
JavaScript
C++
http://ganeshiyer.net

47.
Architecture
JavaScript
C++
JavaScript Engine
http://ganeshiyer.net

48.
Architecture
JavaScript
C++
Event-based fully
asynchronous I/O library.
http://ganeshiyer.net

49.
Architecture
JavaScript
C++
The event loop
http://ganeshiyer.net

50.
Architecture
JavaScript
C++
Exposes OS features like
file handling, sockets
etc. Functionality for
HTTP, DNS etc http://ganeshiyer.net

51.
The EventDriven model
http://ganeshiyer.net

52.
Nodejs
http://ganeshiyer.net

53.
Nodejs: Hello World
http://ganeshiyer.net

54.
Nodejs: Hello World
Output
$ Hello World
http://ganeshiyer.net

55.
Hello World revisited
VS
Synchronous Asynchronous
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56.
Hello World revisited
VS
Output
$ hello
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57.
Hello World revisited
VS
Output
$ hello 2 seconds later
http://ganeshiyer.net

58.
Hello World revisited
VS
Output
$ hello 2 seconds later
$ world
http://ganeshiyer.net

59.
Hello World revisited
VS
Output New request to
Node
$ hello During those two seconds
http://ganeshiyer.net

60.
Hello World revisited
VS
Output New requests
to Node
$ hello During those two seconds
http://ganeshiyer.net

61.
Hello World revisited
VS
Since it is non-blocking
Output
$ hello 2 seconds later $ hello 2 seconds later $ hello 2 seconds later
$ world $ world $ world
Response Response Response
http://ganeshiyer.net

62.
Creating an HTTP server
http://ganeshiyer.net

63.
Creating an HTTP server
Require http
module
http://ganeshiyer.net

64.
Creating an HTTP server
Callback executed on
each request
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65.
Static file serving web server
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66.
Static file serving web server
Parsing
the url for
pathname
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67.
Node provides low-level functionality
For buliding web-applications we require higher
functionality
Node has a lot of packages that help!
http://ganeshiyer.net

68.
Node Ecosystem
http://ganeshiyer.net

69.
Package management with npm
Predominant package manager for node
To install ‘express’ package
http://ganeshiyer.net

70.
Connect.js : Middleware for nodejs
Essential middleware required for developing
web applications
Implements logging, caching, cookies, sessions
etc.
http://ganeshiyer.net

71.
Connect.js : Middleware for nodejs
Essential middleware required for developing web applications
• logger request logger with custom format support
• csrf Cross-site request forgery protection
• basicAuth basic http authentication
• bodyParser extensible request body parser
• json application/json parser
• urlencoded application/x-www-form-urlencoded parser
• cookieParser cookie parser
• session session management support with bundled MemoryStore
• cookieSession cookie-based session support
• staticCache memory cache layer for the static() middleware
http://ganeshiyer.net

72.
Connect.js : Middleware for nodejs
http://ganeshiyer.net

73.
Express.js : A MVC framework for web
Applications
http://ganeshiyer.net

74.
Express.js : A MVC framework for web
Applications
Model View Controller
http://ganeshiyer.net

75.
Express.js : A MVC framework for web
Applications
Model View Controller
Performs RESTful routing
http://ganeshiyer.net

76.
Express.js : A MVC framework for web
Applications
Model View Controller
Performs RESTful routing
Uses Templating for rendering html
http://ganeshiyer.net

77.
Scalability across multiple
cores/servers
http://ganeshiyer.net

78.
Scalability across multiple
cores/servers
Node is single threaded!
http://ganeshiyer.net

79.
Scalability across multiple
cores/servers
Node is single threaded!
How is going to scale on my multi-core server!?
http://ganeshiyer.net

80.
Scalability across multiple
cores/servers
Start child processes on multiple
cores/servers.
One process manages flow of events and
other cores for doing computation.
http://ganeshiyer.net

81.
Scalability across multiple
cores/servers
Cluster is an extensible multi-core server
manager for node.js.
http://ganeshiyer.net

82.
Questions?
http://ganeshiyer.net

83.
Thank You
http://ganeshiyer.net