Agile Computing Authors: Elizabeth White, John Mertic, Pat Romanski, Liz McMillan, Carmen Gonzalez

Related Topics: @CloudExpo, Microservices Expo, Microsoft Cloud

@CloudExpo: Book Excerpt

Cloud Computing, SOA and Windows Azure - Part 3

Windows Azure Roles

For a complete list of the co-authors and contributors, see the end of the article.

A cloud service in Windows Azure will typically have multiple concurrent instances. Each instance may be running all or a part of the service's codebase. As a developer, you control the number and type of roles that you want running your service.

Web Roles and Worker Roles
Windows Azure roles are comparable to standard Visual Studio projects, where each instance represents a separate project. These roles represent different types of applications that are natively supported by Windows Azure. There are two types of roles that you can use to host services with Windows Azure:

  • Web roles
  • Worker roles

Web roles provide support for HTTP and HTTPS through public endpoints and are hosted in IIS. They are most comparable to regular ASP.NET projects, except for differences in their configuration files and the assemblies they reference.

Worker roles can also expose external, publicly facing TCP/IP endpoints on ports other than 80 (HTTP) and 443 (HTTPS); however, worker roles do not run in IIS. Worker roles are applications comparable to Windows services and are suitable for background ­processing.

Virtual Machines
Underneath the Windows Azure platform, in an area that you and your service logic have no control over, each role is given its own virtual machine or VM. Each VM is created when you deploy your service or service-oriented solution to the cloud. All of these VMs are managed by a modified hypervisor and hosted in one of Microsoft's global data centers.

Each VM can vary in size, which pertains to the number of CPU cores and memory. This is something that you control. So far, four pre-defined VM sizes are provided:

  • Small - 1.7ghz single core, 2GB memory
  • Medium - 2x 1.7ghz cores, 4GB memory
  • Large - 4x 1.7ghz cores, 8GB memory
  • Extra large - 8x 1.7ghz cores, 16GB memory

Notice how each subsequent VM on this list is twice as big as the previous one. This simplifies VM allocation, creation, and management by the hypervisor.

Windows Azure abstracts away the management and maintenance tasks that come along with traditional on-premise service implementations. When you deploy your service into Windows Azure and the service's roles are spun up, copies of those roles are replicated automatically to handle failover (for example, if a VM were to crash because of hard drive failure). When a failure occurs, Windows Azure automatically replaces that "unreliable" role with one of the "shadow" roles that it originally created for your service. This type of failover is nothing new. On-premise service implementations have been leveraging it for some time using clustering and disaster recovery solutions. However, a common problem with these failover mechanisms is that they are often server-focused. This means that the entire server is failed over, not just a given service or service composition.

When you have multiple services hosted on a Web server that crashes, each hosted service experiences downtime between the current server crashing and the time it takes to bring up the backup server. Although this may not affect larger organizations with sophisticated infrastructure too much, it can impact smaller IT enterprises that may not have the capital to invest in setting up the proper type of failover infrastructure.

Also, suppose you discover in hindsight after performing the failover that it was some background worker process that caused the crash. This probably means that unless you can address it quick enough, your failover server is under the same threat of crashing.

Windows Azure addresses this issue by focusing on application and hosting roles. Each service or solution can have a Web frontend that runs in a Web role. Even though each role has its own "active" virtual machine (assuming we are working with single instances), Windows Azure creates copies of each role that are physically located on one or more servers. These servers may or may not be running in the same data center. These shadow VMs remain idle until they are needed.

Should the background process code crash the worker role and subsequently put the underlying virtual machine out of commission, Windows Azure detects this and automatically brings in one of the shadow worker roles. The faulty role is essentially discarded. If the worker role breaks again, then Windows Azure replaces it once more. All of this is happening without any downtime to the solution's Web role front end, or to any other services that may be running in the cloud.

Input Endpoints
Web roles used to be the only roles that could receive Internet traffic, but now worker roles can listen to any port specified in the service definition file. Internet traffic is received through the use of input endpoints. Input endpoints and their listening ports are declared in the service definition (*.csdef) file.

Keep in mind that when you specify the port for your worker role to listen on, Windows Azure isn't actually going to assign that port to the worker. In reality, the load balancer will open two ports-one for the Internet and the other for your worker role. Suppose you wanted to create an FTP worker role and in your service definition file you specify port 21. This tells the fabric load balancer to open port 21 on the Internet side, open pseudo-random port 33476 on the LAN side, and begin routing FTP traffic to the FTP worker role.

In order to find out which port to initialize for the randomly assigned internal port, use the RoleEnvironment.CurrentRoleInstance.InstanceEndpoints["FtpIn"].IPEndpoint object.

Inter-Role Communication
Inter-Role Communication (IRC) allows multiple roles to talk to each other by exposing internal endpoints. With an internal endpoint, you specify a name instead of a port number. The Windows Azure application fabric will assign a port for you automatically and will also manage the name-to-port mapping.

Here is an example of how you would specify an internal endpoint for IRC:

<ServiceDefinition xmlns=
ServiceDefinition" name="HelloWorld">
<WorkerRole name="WorkerRole1">
<InternalEndpoint name="NotifyWorker" protocol="tcp" />

Example 1
In this example, NotifyWorker is the name of the internal endpoint of a worker role named WorkerRole1. Next, you need to define the internal endpoint, as follows:

RoleInstanceEndpoint internalEndPoint =
WorkerRole.factory = new ChannelFactory<IClientNotification>(binding);

Example 2
You only need to specify the IP endpoint of the other worker role instances in order to communicate with them. For example, you could get a list of these endpoints with the following routine:

var current = RoleEnvironment.CurrentRoleInstance;
var endPoints = current.Role.Instances
.Where(instance => instance != current)
.Select(instance => instance.InstanceEndpoints["NotifyWorker"]);

Example 3
IRC only works for roles in a single application deployment. Therefore, if you have multiple applications deployed and would like to enable some type of cross-application role communication, IRC won't work. You will need to use queues instead.

Summary of Key Points

  • Windows Azure roles represent different types of supported applications or services.
  • There are two types of roles: Web roles and worker roles.
  • Each role is assigned its own VM.

•   •   •

This excerpt is from the book, "SOA with .NET & Windows Azure: Realizing Service-Orientation with the Microsoft Platform", edited and co-authored by Thomas Erl, with David Chou, John deVadoss, Nitin Ghandi, Hanu Kommapalati, Brian Loesgen, Christoph Schittko, Herbjörn Wilhelmsen, and Mickie Williams, with additional contributions from Scott Golightly, Daryl Hogan, Jeff King, and Scott Seely, published by Prentice Hall Professional, June 2010, ISBN 0131582313, Copyright 2010 SOA Systems Inc. For a complete Table of Contents please visit: www.informit.com/title/0131582313

David Chou is a technical architect at Microsoft and is based in Los Angeles. His focus is on collaborating with enterprises and organizations in such areas as cloud computing, SOA, Web, distributed systems, and security.

John deVadoss leads the Patterns & Practices team at Microsoft and is based in Redmond, WA.

Thomas Erl is the world's top-selling SOA author, series editor of the Prentice Hall Service-Oriented Computing Series from Thomas Erl (www.soabooks.com), and editor of the SOA Magazine (www.soamag.com).

Nitin Gandhi is an enterprise architect and an independent software consultant, based in Vancouver, BC.

Hanu Kommalapati is a Principal Platform Strategy Advisor for a Microsoft Developer and Platform Evangelism team based in North America.

Brian Loesgen is a Principal SOA Architect with Microsoft, based in San Diego. His extensive experience includes building sophisticated enterprise, ESB and SOA solutions.

Christoph Schittko is an architect for Microsoft, based in Texas. His focus is to work with customers to build innovative solutions that combine software + services for cutting edge user experiences and the leveraging of service-oriented architecture (SOA) solutions.

Herbjörn Wilhelmsen is a consultant at Forefront Consulting Group, based in Stockholm, Sweden. His main areas of focus are Service-Oriented Architecture, Cloud Computing and Business Architecture.

Mickey Williams leads the Technology Platform Group at Neudesic, based in Laguna Hills,

Scott Golightly is currently an Enterprise Solution Strategist with Advaiya, Inc; he is also a Microsoft Regional Director with more than 15 years of experience helping clients to create solutions to business problems with various technologies.

Darryl Hogan is an architect with more than 15 years experience in the IT industry. Darryl has gained significant practical experience during his career as a consultant, technical evangelist and architect.

As a Senior Technical Product Manager at Microsoft, Kris works with customers, partners, and industry analysts to ensure the next generation of Microsoft technology meets customers' requirements for building distributed, service-oriented solutions.

Jeff King has been working with the Windows Azure platform since its first announcement at PDC 2008 and works with Windows Azure early adopter customers in the Windows Azure TAP

Scott Seely is co-founder of Tech in the Middle, www.techinthemiddle.com, and president of Friseton, LLC.

More Stories By Thomas Erl

Thomas Erl is a best-selling IT author and founder of Arcitura Education Inc., a global provider of vendor-neutral educational services and certification that encompasses the Cloud Certified Professional (CCP) and SOA Certified Professional (SOACP) programs from CloudSchool.com™ and SOASchool.com® respectively. Thomas has been the world's top-selling service technology author for nearly a decade and is the series editor of the Prentice Hall Service Technology Series from Thomas Erl, as well as the editor of the Service Technology Magazine. With over 175,000 copies in print world-wide, his eight published books have become international bestsellers and have been formally endorsed by senior members of many major IT organizations and academic institutions. To learn more, visit: www.thomaserl.com

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.

@ThingsExpo Stories
Successful digital transformation requires new organizational competencies and capabilities. Research tells us that the biggest impediment to successful transformation is human; consequently, the biggest enabler is a properly skilled and empowered workforce. In the digital age, new individual and collective competencies are required. In his session at 19th Cloud Expo, Bob Newhouse, CEO and founder of Agilitiv, will draw together recent research and lessons learned from emerging and established ...
Enterprise IT has been in the era of Hybrid Cloud for some time now. But it seems most conversations about Hybrid are focused on integrating AWS, Microsoft Azure, or Google ECM into existing on-premises systems. Where is all the Private Cloud? What do technology providers need to do to make their offerings more compelling? How should enterprise IT executives and buyers define their focus, needs, and roadmap, and communicate that clearly to the providers?
One of biggest questions about Big Data is “How do we harness all that information for business use quickly and effectively?” Geographic Information Systems (GIS) or spatial technology is about more than making maps, but adding critical context and meaning to data of all types, coming from all different channels – even sensors. In his session at @ThingsExpo, William (Bill) Meehan, director of utility solutions for Esri, will take a closer look at the current state of spatial technology and ar...
SYS-CON Events announced today that Streamlyzer will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Streamlyzer is a powerful analytics for video streaming service that enables video streaming providers to monitor and analyze QoE (Quality-of-Experience) from end-user devices in real time.
You have great SaaS business app ideas. You want to turn your idea quickly into a functional and engaging proof of concept. You need to be able to modify it to meet customers' needs, and you need to deliver a complete and secure SaaS application. How could you achieve all the above and yet avoid unforeseen IT requirements that add unnecessary cost and complexity? You also want your app to be responsive in any device at any time. In his session at 19th Cloud Expo, Mark Allen, General Manager of...
SYS-CON Media announced today that @WebRTCSummit Blog, the largest WebRTC resource in the world, has been launched. @WebRTCSummit Blog offers top articles, news stories, and blog posts from the world's well-known experts and guarantees better exposure for its authors than any other publication. @WebRTCSummit Blog can be bookmarked ▸ Here @WebRTCSummit conference site can be bookmarked ▸ Here
Cloud based infrastructure deployment is becoming more and more appealing to customers, from Fortune 500 companies to SMEs due to its pay-as-you-go model. Enterprise storage vendors are able to reach out to these customers by integrating in cloud based deployments; this needs adaptability and interoperability of the products confirming to cloud standards such as OpenStack, CloudStack, or Azure. As compared to off the shelf commodity storage, enterprise storages by its reliability, high-availabil...
The IoT industry is now at a crossroads, between the fast-paced innovation of technologies and the pending mass adoption by global enterprises. The complexity of combining rapidly evolving technologies and the need to establish practices for market acceleration pose a strong challenge to global enterprises as well as IoT vendors. In his session at @ThingsExpo, Clark Smith, senior product manager for Numerex, will discuss how Numerex, as an experienced, established IoT provider, has embraced a ...
DevOps is being widely accepted (if not fully adopted) as essential in enterprise IT. But as Enterprise DevOps gains maturity, expands scope, and increases velocity, the need for data-driven decisions across teams becomes more acute. DevOps teams in any modern business must wrangle the ‘digital exhaust’ from the delivery toolchain, "pervasive" and "cognitive" computing, APIs and services, mobile devices and applications, the Internet of Things, and now even blockchain. In this power panel at @...
SYS-CON Events announced today that Super Micro Computer, Inc., a global leader in Embedded and IoT solutions, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 7-9, 2017, at the Javits Center in New York City, NY. Supermicro (NASDAQ: SMCI), the leading innovator in high-performance, high-efficiency server technology, is a premier provider of advanced server Building Block Solutions® for Data Center, Cloud Computing, Enterprise IT, Hadoop/Big Data, HPC and ...
SYS-CON Events announced today that SoftNet Solutions will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. SoftNet Solutions specializes in Enterprise Solutions for Hadoop and Big Data. It offers customers the most open, robust, and value-conscious portfolio of solutions, services, and tools for the shortest route to success with Big Data. The unique differentiator is the ability to architect and ...
In the next forty months – just over three years – businesses will undergo extraordinary changes. The exponential growth of digitization and machine learning will see a step function change in how businesses create value, satisfy customers, and outperform their competition. In the next forty months companies will take the actions that will see them get to the next level of the game called Capitalism. Or they won’t – game over. The winners of today and tomorrow think differently, follow different...
“Media Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. CloudBerry Backup is a leading cross-platform cloud backup and disaster recovery solution integrated with major public cloud services, such as Amazon Web Services, Microsoft Azure and Google Cloud Platform.
In past @ThingsExpo presentations, Joseph di Paolantonio has explored how various Internet of Things (IoT) and data management and analytics (DMA) solution spaces will come together as sensor analytics ecosystems. This year, in his session at @ThingsExpo, Joseph di Paolantonio from DataArchon, will be adding the numerous Transportation areas, from autonomous vehicles to “Uber for containers.” While IoT data in any one area of Transportation will have a huge impact in that area, combining sensor...
More and more brands have jumped on the IoT bandwagon. We have an excess of wearables – activity trackers, smartwatches, smart glasses and sneakers, and more that track seemingly endless datapoints. However, most consumers have no idea what “IoT” means. Creating more wearables that track data shouldn't be the aim of brands; delivering meaningful, tangible relevance to their users should be. We're in a period in which the IoT pendulum is still swinging. Initially, it swung toward "smart for smar...
@ThingsExpo has been named the Top 5 Most Influential M2M Brand by Onalytica in the ‘Machine to Machine: Top 100 Influencers and Brands.' Onalytica analyzed the online debate on M2M by looking at over 85,000 tweets to provide the most influential individuals and brands that drive the discussion. According to Onalytica the "analysis showed a very engaged community with a lot of interactive tweets. The M2M discussion seems to be more fragmented and driven by some of the major brands present in the...
The best way to leverage your Cloud Expo presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering Cloud Expo and @ThingsExpo will have access to these releases and will amplify your news announcements. More than two dozen Cloud companies either set deals at our shows or have announced their mergers and acquisitions at Cloud Expo. Product announcements during our show provide your company with the most reach through our targeted audiences.
November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Penta Security is a leading vendor for data security solutions, including its encryption solution, D’Amo. By using FPE technology, D’Amo allows for the implementation of encryption technology to sensitive data fields without modification to schema in the database environment. With businesses having their data become increasingly more complicated in their mission-critical applications (such as ERP, CRM, HRM), continued ...
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at @ThingsExpo, James Kirkland, Red Hat's Chief Arch...
SYS-CON Events announced today that Enzu will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to focus on the core of their online busine...