ussd renderer redux

USSD Renderer ReduxMobME Engineering Saturdays 002Vishnu Gopal

Agenda

Why Redux?

Implementation

Evented & Synchrony

Redux Internals

Calculator using Redux

Next Steps

Why Redux?

Mobile Network Operator

USSD Device

Mobile Subscriber

USSD App

MobME Server

Why Redux?

Vodafone

Comviva USSD Gateway

98468190XX

USSD Flow

USSD Renderer Redux

Why Redux?Comviva USSD Gateway

USSD Renderer Redux

MS Mobile Subscriber

MS Initiated MS -> USSD Network Initiated USSD -> MS

Request USSD -> MSResponse MS -> USSDNotify USSD -> MS (end)

Why Redux?

Slow, > 5s

Single simple response

Lots of sessions

Stateful

No extra HTTP features.

Fast, < 0.5s

Multiple resources

Minimal sessions

Stateless

Cookies, pipelining, etc.

HTTP USSD

Why Redux?Comviva USSD Gateway

USSD Renderer Redux

Protocol HTTPA USSD Response is converted to a HTTP Request with these

parameters:msisdn, input, shortcode

Why Redux?

http://host:port/ussd-121?msisdn=<msisdn>&input=

“Welcome to 121! Press 1 for Umbrellas and 2 for Raincoats”

http://host:port/ussd-121?msisdn=<msisdn>&input=2

“Thank you for choosing Raincoats. A customer service representative will shortly give you a call.”

Why Redux?

USSDRenderer

Mature, truckload of

featuresPython & YAML

Forking Processes

ProceduralNot TDDed

Why Redux?

USSDRenderer Redux

Baby, subset of features Ruby

Evented

Classes, Modular, Helpers

TDDed

Implementation: Evented

USSD Renderer

Reusable Worker Pool ->

USSD Worker ProcessMS

Worker Exhaustion When Requests are Slow

MS

MS

MS

USSD Worker Process

USSD Worker Process

USSD Worker Process

Implementation: Evented

USSD Renderer

Single Threaded Evented

Worker ->

MS

Can only saturate one core

MS

MS

MS

USSD Worker Process

Less memory, Less CPU

Implementation: Evented

Works the same way CPUs work

Pauses a request and handles another when it is waiting for input and output.

Keyboard input/output

Network requests, like HTTP API calls.

When the request finishes, a callback is fired to let the request know status (error or success)

Implementation: Evented

USSD Renderer

Single Threaded Evented

Worker ->

MS-1 USSD Worker Process

MS-2

Operator Balance

API (slow)

A B

CD

Once C is finished, MS-1 receives a callback on success, errback on failure

Implementation: Evented

a = EM::HTTPRequest.new(“http://google.com/”).get

a.callback { p a.response }

a.errback { p a.response_header.status }

Implementation: Synchrony

a = EM::HTTPRequest.new(“http://google.com/”).get

if a.response_header.status == 500

p “error”

else

p a.response

end

Implementation: Redux

Request

Input

Process

Request Notify

Implementation: Redux

Request

Input

Process

Request

Notify

Node 1Input

Process

Node 2

Implementation: Redux

index {

request {

prompt “Enter your name:”

}

process { |input|

notify “Hello #{input}!”

}

}

Implementation: Reduxindex {

request {

prompt “Enter your name:”

}

process { |input|

session[:name] = input

switch :age

}

}

age {

request {

prompt “Enter your age:”

}

process { |input|

notify “Hello #{input} year old #{session[:name]}”

}

}

Writing a Redux Calculator

Next StepsLots more features!

Menu pagination with prefixes and suffixes

Message interpolation

Redis session store

Lots of helpers for common tasks: redis, mysql, url calls

Play around with the template to create your own USSD app!

Finis.Questions?