Introduction Research Approach More in depth Till now and further on

PhD. ColloquiumTenant-dependent Variability Patterns in Online

Business Software

Jaap Kabbedijk, MSc.

Utrecht University

June 05, 2012

Introduction Research Approach More in depth Till now and further on

Outline

Introduction

Research Approach

More in depthMulti-tenancySoftware Patterns

Till now and further on

Introduction Research Approach More in depth Till now and further on

Who am I?

• Jaap Kabbedijk

• Business Informatics

• PhD. candidate• Multi-tenancy• Online variability• Variability patterns

• Running, Fiction

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Personal

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Introduction Research Approach More in depth Till now and further on

Professional

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Requirements Engineering: Customer Involvement

Kabbedijk J., Brinkkemper S., Jansen S., van der Veldt B. (2009).Customer Involvement in Requirements Management: Lessonsfrom Mass Market Software Development. 17th IEEE InternationalRequirements Engineering Conference, 281-286

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Requirements Engineering: Decision Making

Kabbedijk J., Wnuk K., Regnell B., Brinkkemper S. (2010). WhatDecision Characteristics Influence Decision Making inMarket-Driven Large-Scale Software Product Line Development?16th International Working Conference on RequirementsEngineering: Foundation for Software Quality, 42-53

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Software Ecosystems

Kabbedijk J., Jansen S. (2011). Steering Insight: An Explorationof the ruby Software Ecosystem. 2nd International Conference onSoftware Business. Lecture Notes in Business InformationProcessing(80),44-55

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PaaS: the reason I’m here now

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Product as a Service

• 4 year project

• Started 01/01/2011

• Two perspectives

• Two PhD’s

• NWO/ICT-Regie funded

• Cooperation challenge

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So now I research...

Tenant-dependent Variability Patterns in Online BusinessSoftware

Introduction Research Approach More in depth Till now and further on

Outline

Introduction

Research Approach

More in depthMulti-tenancySoftware Patterns

Till now and further on

Introduction Research Approach More in depth Till now and further on

Research Motivation

• Customers have specific requirements for the software they use

• Offering specific on-premises variants can be hard to:• Manage• Update• Maintain

• Complying to customer specific requirements in a SaaSenvironment has drawbacks:

• Difficulty with scalability• Difficulty with maintainability• Architectural erosion

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Main Project Goal

Minimizing the total cost of ownership (TCO), by profiting ofthe economy of scale of the SaaS deployment model, whilekeeping flexibility in offering functionality to customers

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What will we do?

What will we do in order to answer the question:

“How to facilitate variability in Multi-tenant Software as aService deployments?”

Variability patterns!

Introduction Research Approach More in depth Till now and further on

What will we do?

What will we do in order to answer the question:

“How to facilitate variability in Multi-tenant Software as aService deployments?”

Variability patterns!

Introduction Research Approach More in depth Till now and further on

Case Companies

• AFAS

• Exact

• MP-Objects

• Mendix

• Centric

• 15 others!

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How to get the patterns?

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Gathering patterns

• Through case studies

• Out of literature

• Using the Seminar on Software Patterns

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Evaluating the patterns (1/2)

• Scalability - How does the software product behave if thecustomer base grows?

• Maintainability - How easy can the software be maintainedwhen this pattern is applied?

• Reusability - How is the reuse of parts of the softwareinfluenced when applying this pattern?

• Security - What is the risk in terms of security ofimplementing this pattern?

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Evaluating the patterns (2/2)

• Complexity - How complex is the the implementation of theresulting software product?

• Flexibility - How well can the pattern cope with differentsystem environments?

• Required Changed - How much should be changed to asolution that does not yet implement the pattern?

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How to evaluate them?

• Project workshops

• Case company interviews

• Case company evaluation sessions

• Academic focus groups

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Outline

Introduction

Research Approach

More in depthMulti-tenancySoftware Patterns

Till now and further on

Introduction Research Approach More in depth Till now and further on

Multi-tenancy

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Where do you want to live?

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Pros and cons

House Apartment

Effective use of land - +Privacy + -Infrastructure sharing - +Maintenance cost sharing - +Freedom + -

House:Privacy and FreedomApartment:Cost and Efficiency

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What does this have to do with software?

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Traditional Delivery Life Cycle

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Traditional Deployment Model

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Traditional: Characteristics

• Think about the ‘House’ example

• Customers have to install and update their own software

• Customers manage their own data

• Every customers needs his own server to deploy the product

• Customizations can easily be done per customer

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Traditional: Disadvantages

• High initial costs for customers

• Hard to keep up with updates

• Lack of expert knowledge

• High change of data loss

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Application Server Provider

• Data not responsibility customer

• Application is hosted at a thirdparty

• Multiple products are hosted onthe same machine

• More efficient use of servercompared to the traditional way

• Every customer has his ownproduct on the server

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Different Environments

• Data not responsibility customer

• Everyone uses the sameproduct, but gets his ownenvironment and database

• Only one codebase

• Reasonably scalable

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Multi-user Solution

• Software as a Service (thinkabout the ‘apartment’ example)

• Data not responsibility customer

• A product is offered completelyas a ‘service’

• Possibility to serve large numberof customers with a limitedamount of servers

• Facebook, Grooveshark, etc.

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Perfect Solution?

• Lower cost for customers

• Higher safety of data for the customer

• Efficient server use for the hosting provider

• But...where are the customizations?

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Multi-tenancy

• Data not responsibility customer

• A product is offered completely‘as a service’

• Possibility to serve large numberof customers with a limitedamount of servers

• Tenants (customers) can havespecific functionality

• Combination between the‘house’ and ‘apartment’ example

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Overview ASP to Multi-tenancy

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Multi-tenancy: Holy Grail?

• A hosted solution

• Sharing of:• Hardware• Software• Development Cost• Deployment Cost• Maintenance Cost

• Possibility for variability in theproduct

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Why is not everything multi-tenant?

• It is a hype, but many people do not know what it is exactly

• Great flexibility in a product can make it difficult to maintain

• Single point of failure

• Safety

• But most of all...most companies don’t know HOW toimplement variability!

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What is variability?

• Possibility to adapt a software product to a specific situation• Different platform• Different country• Different customer wishes

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Variability Moments

• During Design - Different product for Linux than forWindows

• During Compilation - Point to different sections of codewhile compiling software for a specific phone

• Linking at installation - Linking a product to severaladditional modules

• Run-time - When a user of an on-line system wants tochange something

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Run-time variability

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How to get the variability in a software product?

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Software Patterns

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It all started in 1977...

• Christopher Alexander

• Architect / Landscapeplanner

• Identified towns ascollections of patterns

• 253 patterns formingtogether a patternlanguage

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Street Cafe

“The street cafe provides a unique setting, special tocities: a place where people can sit lazily, legitimately, beon view, and watch the world go by... Encourage localcafes to spring up in each neighborhood. Make themintimate places, with several rooms, open to a busy path,where people can sit with coffee or a drink and watch theworld go by. Build the front of the cafe so that a set oftables stretch out of the cafe, right into the street.”

Christopher Alexander, A Pattern Language, p. 437,439

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First Software Pattern: MVC

• Model View Controller

• Smalltalk-80

• Data is separate fromrepresentation

• Still used today

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Big break through: GoF

• Gang of Four (1994)

• Gamma, Helm, Johnson,Vlissides

• 23 patterns, became themost famous patterns

• Object Oriented

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GoF examples

• Composite

• Abstract Factory

• Singleton

• Observer

• Memento

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GoF: Describing a pattern

• Name

• Intent - What does the pattern do?

• Motivation - How does the solution solve the problem?

• Applicability - When can the pattern be applied?

• Structure - Graphical representation

• Consequences - What happens when the solution isimplemented? Both benefits and liabilities

• Known Uses - A good example of real use. Preferably indifferent domains

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POSA: A System of Patterns

• Pattern-Oriented SoftwareArchitecture

• Buschman et al.

• Five volumes: 1996 to2007

• Not only OO

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POSA: classification

• Architectural Patterns

• Design Patterns

• Idioms

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Architectural Patterns

“An architectural pattern expresses a fundamentalstructural organization schema for software systems. Itprovides a set of predefined subsystems, specifies theirresponsibilities, and includes rules and guidelines fororganizing the relationships between them.”

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Design Patterns

“A design pattern provides a scheme for refining thesubsystems or components of a software system, or therelationships between them. It describes acommonly-recurring structure of communicatingcomponents that solves a general design problem within aparticular context.”

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Idioms

“An idiom is a low-level pattern specific to aprogramming language. an idiom describes how toimplement particular aspects of components or therelationships between them using the features of thegiven language.”

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Recap

“A pattern is a solution to a problem that arises within aspecific context”

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So, we need...

• Context

• Problem

• Solution

Is this it? Do we miss something?

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We also need

• Goodness

• Recurrence

Until we say something about that, it is still a proto-pattern

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If one of both lacks...

• Bad Pattern

• Dysfunctional Pattern

• Anti-Pattern

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Diagrammability

• Christopher Alexander stated:

“If you can’t draw a diagram of it, it isn’t a pattern”

• Beware...it is not always the other way around

• UML is no silver bullet

• A diagram has to be interpreted, not implemented

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So, what do I want to find?

• Identification - Name and classification for identifying thepattern

• Context - Situation giving rise to a problem

• Problem - Set of forces repeatedly arising in the context

• Solution - Configuration to balance the forces

• Consequences - Consequences arising from application of thepattern. General, but specifically aimed at variability

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But also

• Example(s)

• Diagram(s)

• Details

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Outline

Introduction

Research Approach

More in depthMulti-tenancySoftware Patterns

Till now and further on

Introduction Research Approach More in depth Till now and further on

Publication: Variability in Multi-tenant Environments

Need for Variability

Nee

d f

or

reso

urc

e sh

arin

g

CustomSoftwareSolution

StandardMulti-tenant

Solution

SPLSolution

ConfigurableMulti-tenant

Solution

PA

AS

IAA

Sa

b

a

b

a+b

a = Business Growthb = Customer Requirements Growth

Kabbedijk J., Jansen S. (2011). Variability in Multi-tenantEnvironments: Architectural Design Patterns from Industry.Variability at the 30th International Conference on ConceptualModeling (LNCS), 6999, 151-160

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Pattern Example

• In a warehousing system, customer A wants an SMS to besend to the truck driver when an order is picked, after whichthe order is removed from the system. Customer B howeverdoes not want any SMS to be send, but does want anapproval by a manager before a picked order is removedfrom the system

• How can we solve this workflow related problem?

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Pre/Post Update Hooks (1/3)

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Pre/Post Update Hooks (2/3)

• Intent - To provide the possibility for tenants to have customfunctionality just before or after an event

• Motivation - To let the software product fit the tenantsbusiness processes best, extra actions could be made availableto tenants before or after an event is called

• Solution - The use of a component able of calling othercomponents before and after the update of data. Thetenant-specific modules are listed in a separate table

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Pre/Post Update Hooks (3/3)

• Explanation - See image

• Consequences - Extra optional components have to beavailable in the software system in order to be able toimplement this pattern

• Example - In a bookkeeping program, tenants can choose,whether they want to update a third party service as well byusing a component that uses the API of a third party serviceto make changes there. If so, the FunctionalComponent cancall the third party communicator after an internal update isrequested

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Publication: CQRS

Kabbedijk J., Jansen S., Brinkkemper S. (2012). A Case Study ofthe Variability Consequences of the CQRS Pattern in OnlineBusiness Software. 17th European Conference on PatternLanguages of Programs (EuroPLoP)

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Seminar on Software Patterns

• 26 students in 13 groups

• 16 different case companies

• Reviewed research approach

• Reviewed proto-pattern

• Reviewed draft-paper

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Student Projects

Numerous student projects on:

• Pattern Adoption

• Variability Patterns

• SaaS flexibility

• Variable SaaS pricing

• Multi-tenancy Deployment Patterns

• Multi-tenancy Literature Study

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And now?

• Do something with the patternseminar

• Evaluate patterns

• Publish!

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Questions