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. The Windows Azure Architecture Guide shows you how to do this.

Who This Book Is For

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.  

Why This Book Is Pertinent Now

In general, the cloud has become a viable option for making your applications accessible to a broad set of customers. In particular, Windows Azure now has in place a complete set of tools for developers and IT professionals. Developers can use the tools they already know, such as Visual Studio, to write their applications for the cloud. In addition, Windows Azure provides a complete, simulated environment known as the development fabric that developers can use to locally write, test, and debug their applications before they deploy them to the cloud. There are also tools and an API to manage your Windows Azure accounts. This book shows you how to use all these tools in the context of a common scenario—how to develop a brand new, multi-tenant, SaaS application for Windows Azure.

How This Book Is Structured

"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.

What You Need to Use the Code

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)

Who's Who

As mentioned earlier, this book uses a sample application that illustrates how to implement applications for the cloud. A panel of experts comments on the development efforts. The panel includes a cloud specialist, a software architect, a software developer, and an IT professional. The delivery of the sample application can be considered from each of these points of view. The following table lists these experts.

	Bharath is a cloud specialist. He checks that a cloud-based solution will work for a company and provide tangible benefits. He is a cautious person, for good reasons. "Implementing a single-tenant application for the cloud is easy. Realizing the benefits that a cloud-based solution can offer to a multi-tenant applications is not always so straight-forward".
	Jana is a software architect. She plans the overall structure of an application. Her perspective is both practical and strategic. In other words, she considers the technical approaches that are needed today and the direction a company needs to consider for the future. "It's not easy to balance the needs of the company, the users, the IT organization, the developers, and the technical platforms we rely on."
	Markus is a senior software developer. He is analytical, detail-oriented, and methodical. He's focused on the task at hand, which is building a great cloud-based application. He knows that he's the person who's ultimately responsible for the code. "For the most part, a lot of what we know about software development can be applied to the cloud. But, there are always special considerations that are very important."
	Poe is an IT professional who's an expert in deploying and running applications in the cloud. Poe has a keen interest in practical solutions; after all, he's the one who gets paged at 03:00 when there's a problem. "Running applications in the cloud that are accessed by thousands of users involves some big challenges. I want to make sure our cloud apps perform well, are reliable, and are secure. The reputation of Tailspin depends on how users perceive the applications running in the cloud."

If you have a particular area of interest, look for notes provided by the specialists whose interests align with yours.