Multi-tenant software applications serve different organizations from a single instance and help to save development, maintenance, and administration costs. The architectural concepts of these applications and their relation to emerging platform-as-a-service (PaaS) environments are still not well understood, so that it is hard for many developers to design and implement such an application. Existing attempts at a structured documentation of the underlying concepts are either technology-specific or restricted to certain details. We propose documenting the concepts as a new architectural style. This paper initially describes the architectural properties, elements, views, and constraints of this style. We illustrate how the architectural elements are implemented in current PaaS environments, such as Force.com, Windows Azure, and Google App Engine.

1. Towards an
Architectural Style
for Multi-tenant
Software Systems
Dr.-Ing. Heiko Koziolek
Industrial Software Systems
ABB Corporate Research
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2. Source: salesforce.com
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3. 28.04.2008:
„SAPs neue Mittelstandssoftware
‚Business By Design‘ klemmt“
25.10.2008:
„SAP will sich von
Outsourcing-Tochter trennen“
19.02.2009:
„SAP dementiert Verkaufsstopp
für ‚Business by Design‘“
Source: heise.de
3

4. Single-Tenancy Multi-Tenancy
Tenant1 Tenant2 Tenant3 Tenant1 Tenant2 Tenant3
App App App App
Database Database Database Database
OS OS OS OS
Hardware Hardware Hardware Hardware
4

5. Challenges
Lack of Ad-hoc Technology
Documentation Solutions Focus
5

6. Architectural Styles
An architectural /style is a coordinated set of
 Client Server  Blackboard
architectural constraints that restricts
 Pipe-and-Filter  C2
the roles / features of architectural elements
and the  Peer-to-Peer
allowed relationshipsREST (WWW)
 among those elements
within any architecture that conforms to that style.
 Mobile Code  SPIAR (AJAX) [Fielding2000]
Idea: Multi-tenancy Style
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7. Resource Sharing Elasticity
Architectural
Architectural
Properties
Properties
Maintainability Customizability
7

8. SPOSAD Style for Multi-Tenancy
Client Tier Application Tier Data Tier
Application Multi-tenant
Browser Cache (optional)
Load Balancer
Threads Database
REST
Asynch,
Customization Synch Data
REST Transfer
Meta-Data Meta-Data
Rich Client
Manager
8

9. SPOSAD Style for Multi-Tenancy
Client Tier Application Tier Data Tier
Elasticity Maintainability
Application Multi-tenant
Browser Cache (optional)
Load Balancer
Threads Database
REST
Asynch,
Customization Synch Data
REST Transfer
Meta-Data Meta-Data
Rich Client
Manager
Customizability Resource Sharing 9

10. Multi-tenant Database
Private Table Layout Extension Table Layout Universal Table Layout
10

11. Multi-tenant Database
Private Table Layout Extension Table Layout Universal Table Layout
Account27
AID Name Robot Speed Account33
1 ABC X 20 AID Name
2 DEF Y 50 1 GHI
Account46
AID Name Lines
1 JKM 12
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12. Multi-tenant Database
Private Table Layout Extension Table Layout Universal Table Layout
Industrial-Account
Tenant ID Row Robot Speed
Account-Extension
27 0 X 20
Tenant ID Row AID Name
27 1 Y 50
27 0 1 ABC
27 1 2 DEF Telecommunication-Account
33 0 1 GHI Tenant ID Row Lines
46 0 1 JKM 46 0 12
12

13. Multi-tenant Database
Private Table Layout Extension Table Layout Universal Table Layout
Universal
Tenant ID Table Col1 Col2 Col3 Col4 Col5 Col6
27 0 1 ABC X 20 - -
27 0 2 DEF Y 50 - -
33 1 1 GHI - - - -
46 2 1 JKM 12 - - -
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14. Shared
Single Code Base
Architectural
Architectural Data Resources
Constraints
Properties
STATE
Customization Component Stateless Application Tier
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15. Architectural Trade-offs
Resource Sharing
vs. Security / Availability
Complexity
vs. Time to market
Customizability
vs. Maintainability
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16. Evaluation?
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17. Client Tier Application Tier Data Tier
Virtual Application Customized
Components Oracle RAC
Application Multi-tenant
Browser Cache (optional)
Load Balancer
Threads Database
REST
Asynch,
Customization Synch Data
REST Transfer
Meta-Data Meta-Data
Rich Client
Manager
Universal Table
Runtime Engine
Layout
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18. Client Tier Application Tier Data Tier
Web / Worker Blobs, Tables,
Roles SQL Azure
Application Multi-tenant
Browser Cache (optional)
Load Balancer
Threads Database
REST
Asynch,
Customization Synch Data
REST Transfer
Meta-Data Meta-Data
Rich Client
Manager
Worker Role
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19. Client Tier Application Tier Data Tier
JSP / Servlet,
Google Big Table
Python
Application Multi-tenant
Browser Cache (optional)
Load Balancer
Threads Database
REST
Asynch,
Customization Synch Data
REST Transfer
Meta-Data Meta-Data
Rich Client
Manager
App Engine
Services
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20. …and SAP? ?
27.01.2010
„Mit dem Featurepack 2.5,
das Mitte dieses Jahres erscheint,
bekommt Business ByDesign
eine Multi-Tenant-Architektur“
Peter Lorenz
Leiter SME Solutions SAP
Source: isreport.de
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21. Conclusions
Multi-tenancy as an Architectural Style
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