Microsoft Azure 101
Microsoft has many solutions in the public cloud. The IaaS and PaaS services focus on Azure services, formerly known as Windows Azure, but rightly renamed, as many services are not Windows-centric. Although the focus of this book is on services related to infrastructure, primarily IaaS, this section will provide a high-level overview of all the key Azure services. It’s important to fully understand the capabilities that are available.
Figure 1.6 shows the three main building blocks of the Azure platform along with the networking and traffic management services that enable various types of connectivity. Azure Compute provides the primary compute capabilities, including virtual machines, cloud services, websites, plus the fabric controller, which manages all the virtual machines and hosts that provide the Azure platform. Azure Data Services, as the name suggests, provides storage, backup, and the SQL Server capabilities in the cloud, including relational databases (which are not available in the core Microsoft Azure component). Finally, the Azure App Services provide services such as access control, caching, directory services, and a service bus for communication between components within and outside of Azure. An Azure Marketplace facilitates the buying and selling of Azure applications, components, and datasets.
Figure 1.6 The three main building blocks of the Azure Platform: Azure, App Services, and Data Services
Once you decide what servers, storage, load balancing, and other goodness is needed to run your applications, you need to decide where you want those capabilities hosted. Microsoft has many datacenters distributed throughout the world; Azure applications can run from any of them. There are currently four datacenters in the United States, and two each in Europe and Asia regions. When an application is deployed to Azure, the customer can select where the application should be deployed. All Azure datacenters are paired to provide protection from site failure and data is replicated.
In the next sections, I will introduce you to many of the services available in Azure. Understand that it is a constantly changing service, and my focus is to simply provide you with an idea of the scope of services. For the most up-to-date list of available services and to get more details, visit http://azure.microsoft.com/en-us/services/. Those services I will be covering in detail throughout the book, such as Azure Active Directory, Azure Automation, Azure Traffic Manager, and of course the networking, won’t be covered in this chapter. (I have another 400 or so pages to tell you about those.) Microsoft often releases new services in a preview mode. You need to apply for preview services before you can use them. To check to see the previews that are available and to sign up, use the Preview website here:
http://azure.microsoft.com/en-us/services/preview/
Microsoft Azure Compute
The main building block of the Azure platform is Microsoft Azure itself. Here you’ll find the key capabilities that enable the cloud-based hosting of applications and data. As Azure has evolved, so too has the naming and hierarchy of services. If you were able to look at what Azure was a year ago, the components would seem different from those I’m describing today.
The virtual machine, as shown in Figure 1.7, is the part that actually runs the applications, which could be a website, some custom middleware code, or some legacy application. All of the compute capabilities are enabled through virtual machines, which vary in size. Although virtual machines are directly accessible and used with Azure IaaS, other services, such as PaaS, websites, networking, and so on, are built using virtual machines; they simply may not be visible to you. I will focus on the IaaS virtual machines in this chapter.
Figure 1.7 The main components that make up Microsoft Azure Compute
A web role acts as the web server for your web applications, such as ASP.NET, Classic ASP, PHP, Python, and Node.js. The web role leverages IIS to run the web applications. If you request five instances of a website role for your web application, then behind the scenes, five virtual machines running IIS are created and load balanced, and all run your web code. If in the future you want additional instances, you just request additional instances, and Azure automatically creates new instances of the web role, deploys your custom code, and adds those new instances to the load balancing. Azure websites, which are separate from the web roles, provide a very fast way to deploy a web application.
A worker role is used to run tasks for backend applications that are not IIS web applications but leverage PaaS. As with the web role, when you deploy your application, you tell Azure how many instances of the role you want, and Azure distributes your application to all instances and balances load. Using worker roles, you can run applications such as Java Virtual Machines or Apache Tomcat. This is where the Azure flexibility shines.
You can use any combination of web roles, worker roles, and VMs to support your application. Some applications may only require web roles, some may need web and worker roles, and some can be deployed using just VMs. The point is the flexibility is there to create roles that meet the needs of the application you are deploying.
Azure Compute also features a Mobile Services set. These services are designed to provide the backend for mobile applications running on Windows, iOS, and Android platforms. Numerous services are available; some of the most useful allow integration into authentication services, such as Microsoft and Facebook accounts, and provide the ability to push notifications to devices.
An auto-scale capability allows multiple Azure virtual machines to be grouped together using a construct known as an availability set. Through configuration, you can specify the minimum and maximum number of virtual machines that should run and how scaling should be performed. For example, if CPU requirements in each VM exceed a certain amount, scaling should occur. To accomplish this, you must precreate all the possible virtual machines in the set. The Azure auto-scale then simply stops (deprovisions) and starts them as needed and optimizes your charges so that only the VMs needed are running. As of this writing, auto-scale will not automatically create new instances of virtual machines from a template. Azure does make it easy to request and instantly deploy additional instances of a role. Auto-scale also allows you to leverage the System Center App Controller, and you can programmatically request new instances by writing your own auto-scaling functionality.
The Azure fabric controller itself seems to work magic. As a customer, you can deploy your application, and Azure just spins up as many instances as you say. You can scale up or down at any time. Your service is always available per the Azure “99.95 %” monthly service level agreement (SLA). The operating systems and dependent services are constantly patched and tuned. The magic is enabled by the Azure fabric controller, which itself is a distributed application running on Azure that has a fabric agent that runs on all the virtual machines (except IaaS VMs) and hosts that make up the Azure compute fabric. The fabric controller constantly monitors, and if it sees a problem, it can spin up new instances of a role. If a request is made for more instances of a role, the fabric controller creates the new instances and adds them to the load balancer configuration. The fabric controller handles all patching and updates (again, except those VMs that are IaaS). Patching and updating is a key reason that Azure applications can be covered by the “99.95 %” SLA. You must deploy at least two instances of any role to take advantage of this capability, as the fabric controller will take down one instance, patch it, and then once that instance is running again, take down the other. As you have more and more instances, more instances can be patched simultaneously by grouping role instances in upgrade domains. When patching occurs, all instances within an upgrade domain are brought down and updated at the same time. Then, once complete, the next upgrade