Business considerations for node.js applications

6000 Greenwood Plaza Blvd Suite 110 Greenwood Village, CO 80111 303.798.5458 www.aspenware.com

Business Considerations for Node.js Applications

Michael Filbin [email protected]

Agenda… •  Definitions •  Introduction to Node.js •  Problems it attempts to solve •  Drawbacks and challenges to adoption •  Use cases and case studies •  Hello World example (if time) •  Summary and conclusion


Who Am I? •  Consultant at Aspenware Internet Solutions Inc. •  Background in Open Source technologies •  Currently JavaScript engineer at Pearson •  Member of Linux and Free Software foundations •  Co-founder of Gogy Inc.


Who Are You?


Acknowledgements


Key Terms…

•  API: A collection of publically exposed methods to facilitate use of a library

•  Asynchronous: The execution of a function and its result are not mutually exclusive.

•  JavaScript Runtime: Optimizes and executes JavaScript code

•  Language Binding: Uses of one programming language to ‘wrap’ a library in another

•  Callback: A reference to executable code that is passed as an argument to a function.

•  I/O Operations: Operations that involve reading/writing data through some time of interface.

•  Procedural Programming: Programs are expressed in terms of steps (procedures) to be carried out

•  Event-driven Programming: Execution of a program is carried out in response to events.

•  Blocking Process: A process that prevents the continuation of execution until it returns.

Brief Introduction to Node Business Considerations for Node.js Applications

What Is Node?


What does Node do? •  API for interacting with low-level system libraries

asynchronously •  Leverages features inherent in the JavaScript language •  Intends to manage concurrency, latency, parallelism


1 L1 Cache 3 L2 Cache 14 RAM 250 Hard Disk 41000000 Network 240000000

3 14 250

41000000

240000000

0

50000000

100000000

150000000

200000000

250000000

300000000 Processor C

ycles

Visualizing Latency


Web Application Life Cycle?


Route Request to Controller Action

Make Database Query

Operate on results

Respond to Request

Write to log file

Traditional Scaling Model…



Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results


Make Database Query

Operate on results

Respond to Request

Operate on results

Resource Limited Scaling


Load Balancer

Web Server

App Server

App Server

Database Search Engine

Resource Limited Scaling


Node’s Execution Model •  Using an event loop

•  Event occurs (emitted) •  Non-I/O operations return immediately •  I/O operations defer to libeio or libuv •  I/O interrupt received and callback is executed •  Data returned to client

RESTful Web Services with Node.js

Event 1

…

Event N

libeio

libuv

FS Network Crypto

All on a single thread on a single processor

Event Loop Analogy

RESTful Web Services with Node.js

Node Architecture…

V8 RunLme

libeio

libuv

Async DNS

OpenSSL


Scaling Node Applications:


Load Balancer / Reverse Proxy

Database

App Server

Search Engine

Content Delivery Network (CDN)

Managing Node Dependencies •  ‘Requiring’ external libraries is handled though the

CommonJS module pattern. •  3rd party libraries distributed though NPM package

management tool •  Packages can be installed globally or locally •  Application dependencies can be expressed in a manifest

file (package.json)


Including Dependencies


<script type="text/javascript" src="scripts/myscript.js"></script>

Including Dependencies


// System-wide (global) libraries/modules // Stored in /usr/local/lib/node_modules var path = require('path'); var fileSystem = require('fileSystem') // Local (project) libraries // ./node_modules var restify = require('restify'); var nconf = require('nconf'); // Including scripts from somewhere in // the file system var MyModel = require("./lib/models/MyModel");

Use Cases for Node.js •  Creating REST APIs (JSON APIs) •  Creating chat servers or messaging clients •  Single-page RIA •  Data Streaming


Challenges to Adoption


Evolving API


•  (2012.01.06 – 24.10.2012): 46 Releases! •  Minor, even release number is stable •  Minor, odd release number is development

Windows Support •  Was written originally for *NIX systems •  Node core largely supports WIN, 3rd party libs… not so

much •  Build tools recently switched to better support WIN


Error Handling & Debugging •  Asynchronous code breaks call stacks •  For synchronous code, you must handle exceptions

carefully (try/catch) •  For asynchronous code, you must pass errors around to

callbacks


Example:


outerFunction(arg1, arg2, function (callback){ if(!arg1 || !arg2){ return callback(new Error("Are you forgetting something?")); } else { return innerFunction(ar1, arg2, function (error, data){ if(error){ callback(error); } else { try{ var json = JSON.parse(data) callback(null, json); } catch(error){ callback(error); } } }) }

});

Asynchronous Code is Complex •  Deeply nested callbacks can become difficult to read &

maintain


Single Threaded


Entire Stack Must Be Non-Blocking


Case Studies


Linkedin •  Originally build on Rails Application Framework •  Need to composite service calls for the client •  Persistent socket connections •  Much smaller code base (~50Kb when minified) •  Reduce the amount of memory leak (from mongrel) •  Benchmarked at 20X faster •  Using 10% original resource (from 30 servers to just 3! &

300MB or RAM to just over 30MB) •  More Stable


Node.js ApplicaLon MongoDB Database

Linkedin Mobile Architecture

Credit: Kirin Prasad, Linkedin Mobile Engineer Business Considerations for Node.js Applications

iOS Android Mobile Web

Client Libraries

Mobile Server

Bg. Queue Tracking Data

Service Data Service

Other Process

Yammer •  Similar use case as LinkedIn (cross-domain proxy) •  JSON Out/JSON In


Resources: •  Concurrent Programming for Scalable Web Architectures, Benjamine Erb.

http://berb.github.com/diploma-thesis/community/042_serverarch.html •  Benchmark Comparisons:

http://shootout.alioth.debian.org/u64/benchmark.php?test=all&lang=nodejs&lang2=fsharp


Conclusion


Summation •  Node.js leverages an evented programming model

to handle concurrency and availability •  Because Node does not rely on threads/processes to

scale, it can use considerably fewer resources •  Fewer resources means lower cost •  More concurrent users means greater revenue

potential •  Because node support the real-time web, you can

improve your user’s experience


6000 Greenwood Plaza Blvd Suite 110 Greenwood Village, CO 80111 303.798.5458 www.aspenware.com

Michael Filbin Michael Filbin, Software Developer [email protected]

Business considerations for node.js applications

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