Welcome!

Agile Computing Authors: Elizabeth White, Yeshim Deniz, Liz McMillan, ManageEngine IT Matters, 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=
"http://schemas.microsoft.com/ServiceHosting/2008/10/
ServiceDefinition" name="HelloWorld">
<WorkerRole name="WorkerRole1">
<Endpoints>
<InternalEndpoint name="NotifyWorker" protocol="tcp" />
</Endpoints>
</WorkerRole>
</ServiceDefinition>

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 =
RoleEnvironment.CurrentRoleInstance.
InstanceEndpoints["NotificationService"];
this.serviceHost.AddServiceEndpoint(
typeof(INameOfYourContract),
binding,
String.Format("net.tcp://{0}/NotifyWorker",
internalEndPoint.IPEndpoint));
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

Authors
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,

Contributors
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
DevOps at Cloud Expo – being held October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA – announces that its Call for Papers is open. Born out of proven success in agile development, cloud computing, and process automation, DevOps is a macro trend you cannot afford to miss. From showcase success stories from early adopters and web-scale businesses, DevOps is expanding to organizations of all sizes, including the world's largest enterprises – and delivering real r...
In his opening keynote at 20th Cloud Expo, Michael Maximilien, Research Scientist, Architect, and Engineer at IBM, will motivate why realizing the full potential of the cloud and social data requires artificial intelligence. By mixing Cloud Foundry and the rich set of Watson services, IBM's Bluemix is the best cloud operating system for enterprises today, providing rapid development and deployment of applications that can take advantage of the rich catalog of Watson services to help drive insigh...
As cloud adoption continues to transform business, today's global enterprises are challenged with managing a growing amount of information living outside of the data center. The rapid adoption of IoT and increasingly mobile workforce are exacerbating the problem. Ensuring secure data sharing and efficient backup poses capacity and bandwidth considerations as well as policy and regulatory compliance issues.
SYS-CON Events announced today that Cloud Academy will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Cloud Academy is the industry’s most innovative, vendor-neutral cloud technology training platform. Cloud Academy provides continuous learning solutions for individuals and enterprise teams for Amazon Web Services, Microsoft Azure, Google Cloud Platform, and the most popular cloud computing technologies. Ge...
The 21st International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Machine Learning and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding busin...
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend @CloudExpo | @ThingsExpo, June 6-8, 2017, at the Javits Center in New York City, NY and October 31 - November 2, 2017, Santa Clara Convention Center, CA. Learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
SYS-CON Events announced today that Progress, a global leader in application development, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Enterprises today are rapidly adopting the cloud, while continuing to retain business-critical/sensitive data inside the firewall. This is creating two separate data silos – one inside the firewall and the other outside the firewall. Cloud ISVs ofte...
SYS-CON Events announced today that Interoute has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Interoute is the owner operator of Europe's largest network and a global cloud services platform, which encompasses over 70,000 km of lit fiber, 15 data centers, 17 virtual data centers and 33 colocation centers, with connections to 195 additional partner data centers. Our full-service Unifie...
Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assis...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 21st International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. @ThingsExpo Silicon Valley Call for Papers is now open.
SYS-CON Events announced today that delaPlex will exhibit at SYS-CON's @ThingsExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. delaPlex pioneered Software Development as a Service (SDaaS), which provides scalable resources to build, test, and deploy software. It’s a fast and more reliable way to develop a new product or expand your in-house team.
DevOps is often described as a combination of technology and culture. Without both, DevOps isn't complete. However, applying the culture to outdated technology is a recipe for disaster; as response times grow and connections between teams are delayed by technology, the culture will die. A Nutanix Enterprise Cloud has many benefits that provide the needed base for a true DevOps paradigm.
Existing Big Data solutions are mainly focused on the discovery and analysis of data. The solutions are scalable and highly available but tedious when swapping in and swapping out occurs in disarray and thrashing takes place. The resolution for thrashing through machine learning algorithms and support nomenclature is through simple techniques. Organizations that have been collecting large customer data are increasingly seeing the need to use the data for swapping in and out and thrashing occurs ...
SYS-CON Events announced today that DivvyCloud will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. DivvyCloud software enables organizations to achieve their cloud computing goals by simplifying and automating security, compliance and cost optimization of public and private cloud infrastructure. Using DivvyCloud, customers can leverage programmatic Bots to identify and remediate common cloud problems in rea...
SYS-CON Events announced today that Tintri, Inc, a leading provider of enterprise cloud infrastructure, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Tintri offers an enterprise cloud platform built with public cloud-like web services and RESTful APIs. Organizations use Tintri all-flash storage with scale-out and automation as a foundation for their own clouds – to build agile development environments...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
Every successful software product evolves from an idea to an enterprise system. Notably, the same way is passed by the product owner's company. In his session at 20th Cloud Expo, Oleg Lola, CEO of MobiDev, will provide a generalized overview of the evolution of a software product, the product owner, the needs that arise at various stages of this process, and the value brought by a software development partner to the product owner as a response to these needs.
SYS-CON Events announced today that Cloudistics, an on-premises cloud computing company, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Cloudistics delivers a complete public cloud experience with composable on-premises infrastructures to medium and large enterprises. Its software-defined technology natively converges network, storage, compute, virtualization, and management into a ...
SYS-CON Events announced today that Technologic Systems Inc., an embedded systems solutions company, will exhibit at SYS-CON's @ThingsExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Technologic Systems is an embedded systems company with headquarters in Fountain Hills, Arizona. They have been in business for 32 years, helping more than 8,000 OEM customers and building over a hundred COTS products that have never been discontinued. Technologic Systems’ pr...
SYS-CON Events announced today that Tappest will exhibit MooseFS at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. MooseFS is a breakthrough concept in the storage industry. It allows you to secure stored data with either duplication or erasure coding using any server. The newest – 4.0 version of the software enables users to maintain the redundancy level with even 50% less hard drive space required. The software func...