ii-national online examination system-ascnt10

ASCNT 2010 CDAC NOIDA

C-56/1 & B-30 Sector 62 -Noida

National Online Examination System: An Architectural Perspective

Pradeep Kumar , Pankaj Nirwan , P Govind Raj


Background

• NASSCOM Recommendation to the Government of India• DIT realizing the initiative through C-DAC• Objective: Design and Develop a robust, fault tolerant,

secure, and scalable and an adaptive system through which examinations can be delivered on an “on demand” basis in selected examination centers spread across the country.

• Implementation Phases– Phase 1: Software for conducting exams at National Levels to

be rolled out.– Phase 2: Collaborative environment for collecting Questions

into the question bank.


Why not use Standard LMS ?

• Designed to deliver content and manage the teaching learning process.

• Not designed to handle large system loads• Computer Adaptive Testing is not

incorporated.


Functional Requirements

Result Generation

Exam Conduction

Manage Questions

Matrix/Vector Creation Question Pool Management Module

Admit Card Generation

Registration

Demographic Details Photographs Booking of Exam Slot Payment through Gateway/DD


Non Functional Requirements

• No Vendor Lock in.• Scale Out Vs Scale Up.• Ease of Extendibility• High System Throughput• High Availability• Security/Privacy• Key Escrow Mechanisms


High Level Architecture

• Blaze DS

• Blaze DS

• Remoting Tier

• Flash Player

• Flash Player

• Browser/AIR• Browser/AIR

• UI on Flex

• UI on Flex

• Presentation Tier

• Business Tier

• ORM Hibernate

• ORM Hibernate • D

B• D

B

• Spring Core

• Context

• AOP

• Transaction

• JDBC

• Security • ORM

• ORM

Tier

• Data Tier

• Persistence

• Logging

• Tomcat on Tuned JVM



Blaze DSBlaze DS

Remoting Tier

Flash PlayerFlash Player

Browser/AIRBrowser/AIR

UI on FlexUI on Flex

Presentation Tier

Business Tier

ORM Hibernate

ORM Hibernate DBDB

Spring Core

Context

AOP

Transaction

JDBC

Security ORM

ORM Tier

Data Tier

Persistence

Logging

Tomcat on Tuned JVM

AS3 VO Java



Blaze DSBlaze DS

Remoting Tier




Presentation Tier

Business Tier

ORM Hibernate

ORM Hibernate DBDB

Spring Core

Context

AOP

Transaction

JDBC

Security ORM

ORM Tier

Data Tier

Persistence

Logging

Tomcat on Tuned JVM

AS3 VO



Blaze DSBlaze DS

Remoting Tier




Presentation Tier

Business Tier

ORM Hibernate

ORM Hibernate DBDB

Spring Core

Context

AOP

Transaction

JDBC

Security ORM

ORM Tier

Data Tier

Persistence

Logging

Tomcat on Tuned JVM

AS3 VO Java VO



Blaze DSBlaze DS

Remoting Tier




Presentation Tier

Business Tier

ORM Hibernate

ORM Hibernate DBDB

Spring Core

Context

AOP

Transaction

JDBC

Security ORM

ORM Tier

Data Tier

Persistence

Logging

Tomcat on Tuned JVM

AMF


Business Tier: Spring

• Aspect Orientation Design– Declarative Transaction Management– Security

• Lightweight– Use POJO’s to manage transactions ,

persistence , communication , job scheduling , batch processing etc.

• Productive– Easy to learn.– Jolt’s productivity Award 2006


Security Subsystem

Application Logic

Security Subsystem

LDAP Biometric Authentication

Database Storing Credentials


Security Subsystem Architecture

• Request

• Login Credentials

• Login Credentials are put in Flex User Interface.

• BlazeDS Channel

Authentication

• The BlazeDS Channel Authentication would be done using Spring Security by contacting a User Repository.

• FilterInvocationInterceptor

• URIInterceptor

• MethodSecurityInterceptor

• TransactionProxy

• Spring Security Interceptors


Role Based Access Control

• Access Decision through AcessDecisionManagers– Affirmative Based Access decision Manager– Role Voter

• Grant access of the resource to the user that has the same role as required by the resource


DEPLOYMENT ARCHITECTURE


Horizontal Clustered Environment

LB

LB

Active Passive Clustered Load Balancer based on Apache mod_proxy , mod_proxy _balancer



LB

LB

Tomcat Application ServerLoad Balancing: ByByte / ByRequest

Tomcat 1

Tomcat 1



LB

LB

Design Deviates from conventional HA Solution

Tomcat 1

Tomcat 1

MYSQL


Horizontal Clustered Environment in NOES

LB

LB

Tomcat 1

Tomcat 1

MYSQL

TERRA

COTA

MYSQL


Transparent Clustering


Transparent Clustering

HA is available as a service of JVM


KEY DESIGN PRINCIPLES


Typical Exam Session Performance



No DB I/O during Exam



Hibernate2nd Level

Cache



Async. Commit


ISSUES FACED DURING IMPLEMENTATION


Integrating Flex and Spring

• Integration Flex and Spring– Not intuitive– BlazeDS Extensions were designed– Later , later 2009 community support

• Transaction– MySQL Storage Engines– Transaction Management for Non DB

operations– Use of Self Reference instead of this pointer


Conclusion and Future Work• Exams Conducted

– C-DAC PG Examinations– C-DAC Recruitment Exams

• Across the country in 10 C-DAC Centers for 10 days

– 300 successful runs of Exam Conduction– DOEACC ‘CCC’ Examination at 4 Regional DOEACC

Centers.

• Initial Stress Testing 5,000 users using 2 Tomcat Servers– Trying to scale further

• Efforts in integration with Eucalyptus and federate across different C-DAC/DOEACC Data centres in the country.

• Using Query Optimization with Hibernate on the Fly.


THANK YOU


Aspect Orientated Design

Module 1 Module 1 Module n



Module 1 Module 2 Module n

Security

Logging



Module 1(core Concerns)

Module 2 (Core concerns)

Module n (Core Concerns)

Security (Cross Cutting Concerns)

Logging(Cross Cutting Concerns)


OOD to Model Cross Cutting Concerns

Module 1: Functional Req. Module 2: Functional Req.

Cross Cutting Concern



OOD to Model Cross Cutting Concerns




•Code Scattering•Code Tangling


AOD to Model Cross Cutting Concerns



Aspect

WeavedWeaved


Aspect Orientation at Business Tier

• Logging• Transaction Management

– Declarative Transactions– Annotations (@Transactional

PROPOGATION_LEVEL)

• Access Control Mechanism– Annotations based RBAC at method

invocation level.

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