Windows Azure is often referred to as a platform, but what is actually inside that platform? As you have seen in the previous sections, Windows Azure offers a place where you can run your website, but during the evolution of the platform, more and more features were added. Beside running a client-facing Internet application, it also offers a place where you can run your application code that has no user interface at all (long-running computations or asynchronous tasks), It even offers the possibility of deploying a Windows Server 2008 R2 image to migrate your legacy applications to the cloud and offer the same level of scalability and availability. The underlying infrastructure of every type of role (web, worker, or VM) is a virtual machine that is handled by Windows Azure and that takes care of load balancing and failover. The pricing for every role type is similar and is based on the size of the underlying virtual machine. The details of the pricing models are described in Chapter 7, The Billing Aspect of Windows Azure.
The Windows Azure platform offers three different types of roles:
Web roles
Worker roles
VM roles
This section explains the differences between these different role types.
Web roles run an Internet Information Services web server that can be used to host your frontend web application. It is easy to deploy a web role, and load balancing is included in the offering. You can use both the HTTP and HTTPS protocols.
A worker role is typically used for long-running or asynchronous tasks that require no user input. A common application scenario is a configuration that consists of both web and worker roles, where the web roles are as thin as possible, only handling traffic and being highly responsive to the user. The worker roles take care of the actual work (placing an order, performing a workflow). Queuing mechanisms enable loose coupling and offer you the ability to achieve fine-grained scaling (for example, only scale up your web roles to enhance).
Virtual Machine (VM) roles allow you to deploy your own Windows Server 2008 R2 image to Windows Azure and host it in a hosted service, just like you do with a web or worker role. Applicable scenarios are applications that require OS customizations or native applications running in a standalone fashion. The VM role allows full control of the application environment (for example, registry settings or the old-fashioned .ini files) and enables you to migrate existing applications quickly to Windows Azure and benefit from the PaaS abilities the platform offers. Applications that take a long time to install or that require user input, or applications that are stateless, are suitable candidates to deploy as a VM role. A VM role gives you control over the virtual machine and allows you to build a suitable image from scratch, upload it to Windows Azure, and get it running. You can install software on the VM image and then upload it.
Just like web and worker roles, VM roles benefit from the automation Windows Azure offers, such as load balancing and failover. Full administrator privileges allow you to connect to the VM role and perform OS tweaking and troubleshooting. The cost structure for a VM role is the same as that of web and worker roles, in that you pay by the hour and based on the actual instance size.
Windows Azure offers both a relational Database-as-a-Service feature and a way to synchronize traditional SQL Server databases with SQL Azure databases and vice versa.
Note
The Database-as-a-Service offering used to be called SQL Azure, but in the June 2012 release of Windows Azure, Microsoft decided to rename it to SQL Database.
Windows Azure offers a relational Database-as-a-Service. Windows SQL Database (formerly known as SQL Azure) is a scalable and highly available database service and can be available in just seconds. It is built on top of SQL Server technology and offers (mostly) comparable functionality. The main difference from a developer perspective is that you do not connect to a SQL Server but directly to a database (it is Database-as-a-Service after all). Using SQL Database keeps you from installing, configuring and managing any servers or databases, including mirroring and implementing failover procedures.
SQL Database is still what you expect it to be—a fully relational database system that can be queried by SQL statements (or Linq, of course). After creating a SQL Database, you are able to reach it not only from your cloud application, but also from your on-premises environment. It fits perfectly into a hybrid or distributed scenario where tiers are spread all over on-premises and cloud systems.
Using SQL Database offers the following:
Use the same tools and knowledge you already have, such as the Management Studio and T-SQL: There is no need to learn new technologies or API to use the full power of SQL Database
The ability to grow in size up to 150 GB: SQL Database is getting more and more enterprise-ready both in size of the offered SLAs and high availability
Scale out easily: Using SQL Database Federations drastically simplifies the scaling out to multiple databases to grow beyond the 150 GB limit and to support multi-tenant solutions
Fast creation of databases: Getting a database online is just a click and a few seconds away
Data Sync is a mechanism that provides easy synchronization between SQL Database and SQL Server database premises. Setting up Data Sync is just a matter of configuration and releases you from writing complex database scripts to synchronize and export/import data. Data Sync offers a fine-grained control on what tables or columns to synchronize, or even a subset of rows and columns. Combining Data Sync together with, for example, Traffic Manager, enables you to create geographically wide applications where both application and data are as close as possible to your customers.
Besides SQL Database, Windows Azure also offers other storage capabilities that are secure, highly scalable, and available.
All data in the Windows Azure storage is replicated at least three times in the same datacenter to offer high availability and prevent the loss of data. Window Azure storage offers:
Blobs: A storage service that enables storing any arbitrary data, such as video or other binaries
Tables: A storage service that enables storing information in a tabular fashion with rows and columns
Queue: A storage service that enables messaging between applications or parts of your application
Windows Azure Drive: A storage service that enables users to mount a Blob as a drive
Binary Large Object (blob) storage is a storage service that allows you to store massive data such as video and audio into the cloud in a logical structure and offers you the same advantages as Windows Azure does with its other services, such as availability, scalability, and redundancy.
Table Storage has the ability to store data in a tabular way, with rows and columns. It is possible to store different entities in the same table. It is not possible to create foreign keys between Table Storage tables (a NoSQL database).
Queues provide a way to enable messaging between your services in a reliable way. It can help you build scalable, loosely-coupled applications by implementing message-based communication between parts of your application.
Windows Azure drive allows you to mount a blob as an NTFS VHD, and a drive letter is assigned to it. You can use traditional IO API (System.IO namespace) to manipulate Windows Azure drive.
We will go into much more detail and provide different code examples on how to use Windows Azure Storage in Chapter 4, Storing Your Data.
SQL Azure reporting allows you to enrich your Windows Azure application with reporting capabilities in a way you did before, by using SQL server reporting 2008 R2. This removes the need for on-premises installations of reporting servers but still enables you to create rich reports with tables, charts, and other compelling visualizations, and to additionally scale your reports and benefit from the underlying Windows Azure Platform-as-a-Service capabilities.
SQL Database reporting offers you the ability to:
Benefit from the pay-per-use philosophy that Windows Azure offers
Take advantage of the scalability and high availability the platform offers
Generate reports in multiple file formats, such as Excel, Word, and PDF
Make use of the same tools as Business Intelligence Design Studio
Provide access to reports and data in a secure, authenticated, and authorized manner
The Windows Azure platform offers a powerful mechanism to build secure messaging and relay capabilities for your distributed and loosely coupled applications. Applications may be on-premises, in the cloud or hybrid.
Integrate your enterprise application, running in your own datacenters, with applications running on Windows Azure. Use the Service Bus to build applications that can scale out more easily and reduce dependencies between components within your distributed applications.
Service Bus offers brokered messaging, meaning a scalable way to store messages, and the ability to implement a publish/subscribe pattern by using topics and subscriptions, allowing you to publish messages to hundreds of subscribers. Beside messaging, Service Bus also offers relayed messaging, enabling your applications running on Windows Azure to call back to applications running inside your datacenter. It lowers the burden on maintaining NATs and firewalls, keeping you focused on the actual business value of your applications.
Content delivery networks (CDNs) enable you to move your data close to your clients. There are multiple CDN nodes all over the world, and the CDN caches your data at locations as close to your customers as possible, to enhance performance. CDN can cache static content like pictures, movies, and software, as well as streaming media. CDN can be turned on, both on hosted services and storage accounts. Enabling CDN on your data is just a click away in the Windows Azure portal; see the following screenshot:
Windows Azure offers a caching mechanism that is distributed and in-memory. It is distributed, because the physical memory of different servers can be used as a single entity. It is in memory, because the cached items are stored in physical memory only and will not be swapped to disk or whatsoever, to keep up the high performance.
Using caching can speed up your application and minimize the round trips needed to your database or other stores. Typical candidates for caching are frequently used, read-only data (such as lookup tables), user session data (such as a shopping cart), and typical application data that requires a "singleton" approach.
Virtual network offers networking capabilities that help you migrate and integrate applications and release you from the plumbing burden of low-level networking issues.
Virtual network consists of two major concepts:
Windows Azure Connect
Traffic Manager
New features were added in June 2012 and are mentioned in Chapter 11, What's New in Windows Azure.
Windows Azure Connect (WAC) enables you to create network connectivity between applications running on Windows Azure and resources in your own datacenter. Setting up a "secure" connection based on IPSec between Windows Azure roles (web, worker, or VM) requires an agent to be installed on your local, on-premises machine that needs to be reached from the cloud. This mechanism does not require any changes to your network topology. Consider WAC as being a VPN, not on a gateway level but on a machine level.
Windows Azure Traffic Manager (WATM) enables fine-grained control on load balancing incoming traffic to multiple hosted services. By default, Windows Azure load balances all incoming web requests equally over the role instances. WATM enables load balancing across different hosted services with different DNS names. This can enhance performance (reducing network latency, but increasing the necessary hops) and availability by setting up "standby" hosted services that handle incoming requests if your primary hosted service is completely down.
By managing the traffic to your services, it is possible to ensure high performance, availability, and robustness of your services. WATM can provide a failover mechanism when it detects that one of your services is down. WATM detects some when a service is down and immediately reroutes traffic to the next closest (configured) service.
WATM policies can be set up on the Windows Azure portal very quickly and offer you three types of load balancing methods:
Based on performance: WATM directs traffic to the hosted service with the least internet latency. Remember that this is only applicable if your hosted service is deployed in multiple Windows Azure regions.
Based on failover: Traffic is directed to one single hosted service, but when the WATM is unable to detect a "heartbeat", it changes the DNS records and redirects all the traffic to the hosted service next in line. When this phenomenon occurs, your application will be unavailable for a few minutes, since the WATM needs to detect the heartbeat failure and update the DNS records.
Based on round robin: The WATM uses a round-robin algorithm to equally spread traffic among every hosted service configured in the policy, as defined in the Windows Azure portal. When a listed hosted service is unavailable (no heartbeat), it is automatically removed from the round-robin list.
Windows Azure Active Directory (WAAD) is a cloud service that offer identity and access functionality to both Windows Azure applications, on-premise applications, applications in a hybrid scenario, and even to Microsoft Office 365, the online SaaS equivalent to Microsoft Office. WAAD relies on the proven technology and capabilities of Active Directory, so that migrating your application to the cloud can be made easier.
Access Control Services (ACS) can offer end users a single sign-on experience across all cloud and hybrid applications. You can move your authentication and authorization logic away from your core applications and make it highly configurable by moving it to ACS. ACS is built on open industry standards, such as WS-Trust and WS-Federation, and SAML 2.0 and Simple Web Token, allowing non-Microsoft programming languages to access the WAAD capabilities as well. An internet portal is available, allowing you to set up authentication and authorization rules outside the boundaries of your application.
ACS offers you:
Single sign-on capabilities: Moving away from custom identity stores and authorization logic enables you to focus on the core functionality of your application.
Interoperability with your corporate Active Directory via ADFS: Allowing you to deploy, for example, your intranet applications to cloud and still maintain the single sign-on experience.
Incorporation of identity providers: Enabling you to make use of popular social media such as Facebook and identity, such as Google, Yahoo!, and Windows Live ID. A detailed example of using Facebook as an identity provider is given in Chapter 6, Key Features Explained.
Windows Azure Marketplace allows you to access SaaS applications and datasets comparable with an app store. You can also offer your applications on the marketplace and open up a global market for your product and/or datasets. Windows Azure Marketplace allows you to:
Access datasets and services from third parties: Security, audit trails (who accessed what resource at which time), billing, and authentication are handled by the Marketplace and let you focus on your application. Open standards such as OAuth and OData allow you to reach beyond platform borders.
Quickly monetize your SaaS solution or datasets and enable financial transactions all over the world in different currencies: Create trial offers and terms of use, and report on usage, traffic, and sales.
Search for data or services that suit your needs.