Developing MyTrafficCamLeong Hean Hong

#HackerspaceJB #HSJB

About

● MTC shows traffic condition for JB-SG travellers

● MTC aggregates cameras from different sources

● I talk about how it works● Share collected data● Describe some of the challenges

System Design

Sponsor: JLP Technologies

System Design

● Camera sources○ LTA (Singapore)○ LLM (Malaysia)○ Own camera @ Menara Cyberport

● Providing feed to○ Mobile clients (iOS + Android)○ Partner’s website

Sponsor: Common Extract

Components In Web Service

Sponsor: Hongineer

Software Stack

● CentOS● Apache● PHP 5.2

○ GluePHP (micro-framework)○ Twig Templating library

Sponsor: Property.cc

Development Tools

● Sublime Text○ Programming editor

● Filezilla○ For deployment on production server

● Git○ Source control

● Bitbucket○ Free private repo○ Code backup

Defining API

● Client makes request via HTTP● Response in JSON● API specifications documented in Google

Doc○ Establish standardization across team

Defining API

CodeFu Techniques

Time-sensitive Photopublic static function photoURL($camId) {

$time = time();

return "/photo/{$camId}/{$time}/".self::genHash($camId, $time);

}

Add timestamp to photo URL, expires in 5 seconds

Tie Photo To Client’s IPpublic static function photoURL($camId) {

return strtr('http://:host/v1api/photo/:camId/:hash', array(

':host' => $_SERVER['HTTP_HOST'],

':camId' => $camId,

':hash' => self::photoHash($camId)

));

}

protected static function photoHash($camId) {

return sha1(self::HASH_KEY.$camId.$_SERVER['REMOTE_ADDR']);

}

Prevent reuse of photo across devices

Rate-limiting Control

● Log IP address● Allow not more than 10 requests per second

per IP○ Currently we have only 6 cameras

AnalyticsGrowing from 6K to 8K visitors

Busy night...

Analytics

More traffic in Sat/Sun

Challenges

● LLM Camera down frequently● Need more cameras● Cost of running MTC

Challenges

Running Out Of Bandwidth

18.50 GB in July 2014

1.73 GB from single host

Feedbacksupport@mytrafficcam.com