Microsoft Azure: Enterprise Application Development: Straight talking advice on how to design and build enterprise applications for the cloud

Before we hop into the cloud, let's talk about who this book is for. Who are "enterprise developers"? In the United States, over half of the economy is small businesses, usually privately owned, with a couple dozen of employees and revenues up to the millions of dollars. The applications that run these businesses have lower requirements because of smaller data volumes and a low number of application users. A single server may host several applications. Many of the business needs for these companies can be met with off-the-shelf software requiring little to no modification.

The minority of the United States economy is made up of huge publicly owned corporations–think Microsoft, Apple, McDonald's, Coca-Cola, Best Buy, and so on. These companies have thousands of employees and revenues in the billions of dollars. Because these companies are publicly owned, they are subject to tight regulatory scrutiny. The applications utilized by these companies must faithfully keep track of an immense amount of data to be utilized by hundreds or thousands of users, and must comply with all matters of regulations. The infrastructure for a single application may involve dozens of servers. A team of consultants is often retained to install and maintain the critical systems of a business, and there is often an ecosystem of internal applications built around the enterprise systems that are just as critical. These are the applications we consider to be "enterprise applications", and the people who develop and extend them are "enterprise developers". The high availability of cloud platforms makes them attractive for hosting these critical applications, and there are many options available to the enterprise developer. This books focuses on Microsoft's cloud development platform named Azure. Throughout this book, we'll develop a simple example application as an introduction to the different facets of Microsoft's Windows Azure platform, and we'll also discuss concepts useful to the enterprise developer, including security and costs, during the course of our application's development.

At its most basic, cloud computing is moving applications accessible from our internal network onto an internet (cloud)-accessible space. We're essentially renting virtual machines in someone else's data center, with the capabilities for immediate scale-out, failover, and data synchronization. In the past, having an Internet-accessible application meant we were building a website with a hosted database. Cloud computing changes that paradigm–our application could be a website, or it could be a client installed on a local PC accessing a common data store from anywhere in the world. The data store could be internal to our network or itself hosted in the cloud. The following diagram outlines three ways in which cloud computing can be utilized for an application. In option 1, both data and application have been hosted in the cloud, the second option is to host our application in the cloud and our data locally, and the third option is to host our data in the cloud and our application locally.

The expense (or cost) model is also very different. In our local network, we have to buy the hardware and software licenses, install and configure the servers, and finally we have to maintain them. All this counts in addition to building and maintaining the application! In cloud computing, the host usually handles all the installation, configuration, and maintenance of the servers, allowing us to focus mostly on the application. The direct costs of running our application in the cloud are only for each machine-hour of use and storage utilization.

The individual pieces of cloud computing have all been around for some time. Shared mainframes and supercomputers have for a long time billed the end users based on that user's resource consumption. Space for websites can be rented on a monthly basis. Providers offer specialized application hosting and, relatively recently, leased virtual machines have also become available. If there is anything revolutionary about cloud computing, then it is its ability to combine all the best features of these different components into a single affordable service offering.

Cloud computing sounds great so far, right? So, what are some of the tangible benefits of cloud computing? Does cloud computing merit all the attention? Let's have a look at some of the advantages:

Cloud computing sounds wonderful so far, but nothing is perfect. There are aspects of cloud computing that will involve compromising, and in some cases, may make cloud computing infeasible for a company; let's have a look at a few of those:

Cloud computing requires more than just a server room, and the different providers employ different technologies. In all cases, cloud computing relies on data centers in multiple geographic locations, with multiple redundancies of everything. It's quite a challenge to locate an area that is geologically stable and relatively free from severe weather events or other natural disasters, making redundancies of locations, in addition to redundancies of utilities, a necessity.

Cloud data centers have moved away from the "racks-in-a-room" or "raised floor" design of traditional data centers. One of the more common designs for cloud data centers is to modify a shipping container to hold racks of servers, and then linking multiple containers together into a large center. The container-based design is used more for stability, space efficiency, and physical isolation of machines. A forty-foot tall rack of servers would be highly unstable and extremely difficult to manage. But a stack of four containers is very stable, and each container is as easy to manage as a small server room. It's also more efficient to cool a number of small rooms as compared to a giant warehouse.

For Azure, Microsoft has taken the container concept a little farther. Microsoft's Azure containers (called Generation 4 Modular Data Centers or G4MDC) are not based on a shipping container, although the end design resembles one. Technically, Microsoft's containers are classified as air handling units and the servers as heaters. Cooling is achieved by pulling outside air through filters, into the container, and around the servers at high velocity. In fact, some of Microsoft's new data centers won't even have roofs! Each G4MDC unit is completely self-contained with airflow regulation, and its own connections for power and bandwidth. Each 40-foot unit can accommodate up to 2,000 servers, and some of Microsoft's facilities will house 400,000 to 500,000 servers.

Usually, cloudy skies are a bad thing–many a day at the beach has been ruined by an abundance of clouds. But in the case of cloud computing, the more clouds, the better! The number of providers of cloud computing services is increasing, but for the enterprise developer, the three major options at the time of writing are from Google, Amazon, and Microsoft.

Google's cloud offering is named the Google AppEngine, and currently supports Python and Java languages. Data are stored in the Google AppEngine data store, a proprietary database utilizing Google Query Language (GQL). For the interested developer, Google offers a free plan with multiple applications.

Amazon has several cloud offerings, all under the Amazon Web Services umbrella, including Simple DB, Elastic Compute Cloud (EC2), Simple Storage Service (S3), and Amazon Virtual Private Cloud (VPC). Simple DB and S3 are data-storage options that are used for everything from compressed backup locations to simple content delivery networks. EC2 is a service that allows us to create a virtual machine to our specifications, and upload it to our cloud-hosting account. We are still completely responsible for the care and feeding of our VM, but Amazon provides the hosting infrastructure. The Amazon VPC is our own private IP block carved out of Amazon's Web Services. The Amazon VPC can be made part of our local network by means of VPN from our firewall to our isolated cloud storage, gaining much of the benefits of cloud storage with the convenience of a local network resource.

Last but not least (and the star of this book) is Microsoft's Azure. Azure actually comprises three services, each of which can be used independently or combined into a completely cloud-based application. When most people speak of Azure, they're speaking of Windows Azure, which is the operating system, application hosting as well as simple storage services. The second piece of Azure is one that has generated a great deal of excitement—SQL Azure. SQL Azure is an almost feature complete version of SQL Server 2008. The final piece of the Windows Azure platform is the

AppFabric, which provides connection and authentication services along with the Service Bus–an enterprise service bus implementation capable of bridging two different enterprises.

There have been many products and services making great promises to the enterprise developer, and a lot of the chatter about cloud computing at times makes it seem like this is yet another buzzword that will pass. Looking at the companies that have made the move to the various cloud platforms makes us think otherwise. Even before its official release, companies such as Domino's, Kelly Blue Book, and Coca-Cola Enterprises had already adapted applications for Azure, and many more case studies were posted from PDC 2009. To underscore the flexibility of the Azure platform, Domino's application is written in Java and served by Tomcat.

No cloud computing platform can be all things to all people. Each platform differs in its capabilities and service offerings, and price can be a factor as well. Enterprise applications typically include a database back end, and Google's lack of a relational database and limited language support (Python and some flavors of Java) make it a tough sell for enterprises that require a full database and use .NET technologies. With Amazon's services, we need to build our own virtual machine (or start with a pre-built one), but we are still responsible for licensing costs, removing the price advantage. Microsoft's Azure platform is designed to be a very happy medium–a wide range of languages can be used, there are no licensing costs, and Azure has some advanced features such as Access Control and Service Bus not found in other cloud offerings. One thing is for sure–with three big players in the cloud computing game, the services will become more feature rich, less expensive, and in the end, the consumers will benefit greatly.

The presence of so many large applications in the cloud is not proof positive enough to conclude that cloud computing is the way of the future, but such rapid adoption speaks well of the advantages of cloud-based applications, especially the time to develop them. The promise of cloud computing platforms is that they are stable, scalable, easy to develop, and are cost effective. Time will tell which providers perform the best, but even at this early stage there are plenty of case studies to observe.

This chapter served as an overview of cloud computing, from a definition to covering a few advantages and disadvantages. We delved a little into the physical infrastructure of a cloud data center and finished up with a brief overview of the three main enterprise providers (Google, Amazon, and Microsoft). The cloud computing offerings have emerged and grown in a very short period of time, sparking not only a great deal of conversation, but also a fair amount of adoption.