Developing Applications for the Cloud on the Microsoft Windows Azure™ Platform

Developing Applications for the Cloud on the Microsoft Windows Azure™ Platform


patterns & practices Developer Center

August 2010


How can a company create an application that has truly global reach and that can scale rapidly to meet sudden, massive spikes in demand? Historically, companies had to invest in building an infrastructure capable of supporting such an application themselves and, typically, only large companies would have the available resources to risk such an enterprise. Building and managing this kind of infrastructure is not cheap, especially because you have to plan for peak demand, which often means that much of the capacity sits idle for much of the time. The cloud has changed the rules of the game: by making the infrastructure available on a “pay as you go” basis, creating a massively scalable, global application is within the reach of both large and small companies.

The cloud platform provides you with access to capacity on demand, fault tolerance, distributed computing, data centers located around the globe, and the capability to integrate with other platforms. Someone else is responsible for managing and maintaining the entire infrastructure, and you only pay for the resources that you use in each billing period. You can focus on using your core domain expertise to build and then deploy your application to the data center or data centers closest to the people who use it. You can then monitor your applications, and scale up or scale back as and when the capacity is required.

Yes, by moving applications to the cloud, you’re giving up some control and autonomy, but you’re also going to benefit from reduced costs, increased flexibility, and scalable computation and storage. This guide shows you how to do this.


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This book is the second volume in a planned series about Windows Azure™ technology platform. Volume 1, Moving Applications to the Cloud on the Windows Azure Platform, provides an introduction to Windows Azure, discusses the cost model and application life cycle management for cloud-based applications, and describes how to migrate an existing ASP.NET application to the cloud. This book demonstrates how you can create from scratch a multi-tenant, Software as a Service (SaaS) application to run in the cloud by using the latest versions of the Windows Azure tools and the latest features of the Windows Azure platform. The book is intended for any architect, developer, or information technology (IT) professional who designs, builds, or operates applications and services that run on or interact with the cloud. Although applications do not need to be based on the Microsoft® Windows® operating system to work in Windows Azure, this book is written for people who work with Windows-based systems. You should be familiar with the Microsoft .NET Framework, Microsoft Visual Studio® development system, ASP.NET MVC, and Microsoft Visual C#® development tool.

Common Scenarios


“The Tailspin Scenario” introduces you to the Tailspin company and the Surveys application. It provides an architectural overview of the Surveys application; the following chapters provide more information about how Tailspin designed and implemented the Surveys application for the cloud. Reading this chapter will help you understand Tailspin’s business model, its strategy for adopting the cloud platform, and some of its concerns.

“Hosting a Multi-Tenant Application on Windows Azure” discusses some of the issues that surround architecting and building multi-tenant applications to run on Windows Azure. It describes the benefits of a multi-tenant architecture and the trade-offs that you must consider. This chapter provides a conceptual framework that helps the reader understand some of the topics discussed in more detail in the subsequent chapters.

“Accessing the Surveys Application” describes some of the challenges that the developers at Tailspin faced when they designed and implemented some of the customer-facing components of the application. Topics include the choice of URLs for accessing the surveys application, security, hosting the application in multiple geographic locations, and using the Content Delivery Network to cache content.

“Building a Scalable, Multi-Tenant Application for Windows Azure” examines how Tailspin ensured the scalability of the multi-tenant Surveys application. It describes how the application is partitioned, how the application uses worker roles, and how the application supports on-boarding, customization, and billing for customers.

“Working with Data in the Surveys Application” describes how the application uses data. It begins by describing how the Surveys application stores data in both Windows Azure tables and blobs, and how the developers at Tailspin designed their storage classes to be testable. The chapter also describes how Tailspin solved some specific problems related to data, including paging through data, and implementing session state. Finally, this chapter describes the role that SQL Azure™ technology platform plays in the Surveys application.

“Updating a Windows Azure Service” describes the options for updating a Windows Azure application and how you can update an application with no interruption in service.

“Debugging and Troubleshooting Windows Azure Applications” describes some of the techniques specific to Windows Azure applications that will help you to detect and resolve issues when building, deploying, and running Windows Azure applications. It includes descriptions of how to use Windows Azure Diagnostics and how to use Microsoft IntelliTrace™ with applications deployed to Windows Azure.

Audience Requirements

The book is intended for any architect, developer, or information technology (IT) professional who designs, builds, or operates applications and services that run on or interact with the cloud. Although applications do not need to be based on the Microsoft® Windows® operating system to work in Windows Azure, this book is written for people who work with Windows-based systems. You should be familiar with the Microsoft .NET Framework, Microsoft Visual Studio® development system, ASP.NET MVC, and Microsoft Visual C#® development tool.

System Requirements

These are the system requirements for running the scenarios:

  • Microsoft Windows Vista SP1, Windows 7, or Microsoft Windows Server® 2008 (32-bit or 64-bit)
  • Microsoft Internet Information Services (IIS) 7.0
  • Microsoft .NET Framework 4 or later
  • Microsoft Visual Studio 2010
  • Windows Azure Tools for Microsoft Visual Studio 2010
  • ASP.NET MVC 2.0
  • Windows Identity Foundation
  • Microsoft Anti-Cross Site Scripting Library
  • Moq (to run the unit tests)
  • Enterprise Library Unity Application Block (binaries included in the samples)

Design Goals

Tailspin is a fictitious startup ISV company of approximately 20 employees that specializes in developing solutions using Microsoft® technologies. The developers at Tailspin are knowledgeable about various Microsoft products and technologies, including the .NET Framework, ASP.NET MVC, SQL Server®, and Microsoft Visual Studio® development system. These developers are aware of Windows Azure but have not yet developed any complete applications for the platform.

The Surveys application is the first of several innovative online services that Tailspin wants to take to market. As a startup, Tailspin wants to develop and launch these services with a minimal investment in hardware and IT personnel. Tailspin hopes that some of these services will grow rapidly, and the company wants to have the ability to respond quickly to increasing demand. Similarly, it fully expects some of these services to fail, and it does not want to be left with redundant hardware on its hands.


The Surveys application enables Tailspin’s customers to design a survey, publish the survey, and collect the results of the survey for analysis. A survey is a collection of questions, each of which can be one of several types such as multiple-choice, numeric range, or free text. Customers begin by creating a subscription with the Surveys service, which they use to manage their surveys and to apply branding by using styles and logo images. Customers can also select a geographic region for their account, so that they can host their surveys as close as possible to the survey audience. The Surveys application allows users to try out the application for free, and to sign up for one of several different packages that offer different collections of services for a monthly fee.

Customers who have subscribed to the Surveys service (or who are using a free trial) access the Subscribers website that enables them to design their own surveys, apply branding and customization, and collect and analyze the survey results. Depending on the package they select, they have access to different levels of functionality within the Surveys application. Tailspin expects its customers to be of various sizes and from all over the world, and customers can select a geographic region for their account and surveys.

The architecture of the Surveys Application is straightforward and one that many other Windows Azure applications use. The core of the application uses Windows Azure web roles, worker roles, and storage. Figure below shows the three groups of users who access the application: the application owner, the public, and subscribers to the Surveys service (in this example, Adatum and Fabrikam).

It also highlights how the application uses SQL Azure™ technology platform to provide a mechanism for subscribers to dump their survey results into a relational database to analyze the results in detail. This guide discusses the design and implementation in detail and describes the various web and worker roles that comprise the Surveys application.


Some of the specific issues that the guide covers include how Tailspin implemented the Surveys application as a multi-tenant application in Windows Azure and how the developers designed the application to be testable. The guide describes how Tailspin handles the integration of the application’s authentication mechanism with a customer’s own security infrastructure by using a federated identity with multiple partners model. The guide also covers the reasoning behind the decision to use a hybrid data model that uses both Windows Azure Storage and SQL Azure. Other topics covered include how the application uses caching to ensure the responsiveness of the Public website for survey respondents, how the application automates the on-boarding and provisioning process, how the application leverages the Windows Azure geographic location feature, and the customer-billing model adopted by Tailspin for the Surveys application.


This guide, like many patterns & practices deliverables, is associated with a community site. On this community site, you can post questions, provide feedback, or connect with other users for sharing ideas. Community members can also help Microsoft plan and test future guides, and download additional content such as extensions and training material.

Future Plans

An extension to this scenario is being developed for mobile users using Windows Phone 7 devices. Early versions of this are available here:

A third part is planned to cover integration scenarios as well as new capabilities. Check the community site for updates.

Feedback and Support

Questions? Comments? Suggestions? To provide feedback about this guide, or to get help with any problems, please visit the Windows Azure guidance Community site. The message board on the community site is the preferred feedback and support channel because it allows you to share your ideas, questions, and solutions with the entire community. This content is a guidance offering, designed to be reused, customized, and extended. It is not a Microsoft product. Code-based guidance is shipped “as is” and without warranties. Customers can obtain support through Microsoft Support Services for a fee, but the code is considered user-written by Microsoft support staff.

Authors and Contributors

This guide was produced by the following individuals:

  • Program and Product Management: Eugenio Pace
  • Architect: David Hill
  • Subject Matter Experts: Dominic Betts, Scott Densmore, Ryan Dunn, Steve Marx, and Matias Woloski
  • Development: Federico Boerr (Southworks), Scott Densmore, Matias Woloski (Southworks)
  • Test team: Masashi Narumoto, Kirthi Royadu (Infosys Ltd.), Lavanya Selvaraj (Infosys Ltd.)
  • Edit team: Dominic Betts, RoAnn Corbisier, Alex Homer, and Tina Burden
  • Book design and illustrations: Ellen Forney, John Hubbard (eson), Katie Niemer and Eugenio Pace.
  • Release Management: Richard Burte

We want to thank the customers, partners, and community members who have patiently reviewed our early content and drafts. Among those, we want to highlight the exceptional contributions of David Aiken, Graham Astor (Avanade), Edward Bakker (Inter Access), Vivek Bhatnagar (Microsoft), Patrick Butler Monterde (Microsoft), Shy Cohen, James Conard, Brian Davis (Longscale), Aashish Dhamdhere (Windows Azure, Microsoft), Andreas Erben (DAENET), Giles Frith , Eric L. Golpe (Microsoft), Johnny Halife (Southworks), Alex Homer, Simon Ince, Joshy Joseph, Andrew Kimball, Milinda Kotelawele (Longscale), Mark Kottke (Microsoft), Chris Lowndes (Avanade), Dianne O’Brien (Windows Azure, Microsoft), Steffen Vorein (Avanade), Brad Wilson (ASP.NET Team), Michael Wood (Strategic Data Systems).

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