P&P: Developing Applications for the Cloud September 22nd, 2010

Vinod Kumar

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 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. 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.

"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.

Click here to download this release.

An extension to this scenario is being developed for mobile users using Windows Phone 7 devices. Early versions of this are available here: http://wp7guide.codeplex.com

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