|By Thomas Erl||
|August 28, 2010 10:00 AM EDT||
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.
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.
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 (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:
<InternalEndpoint name="NotifyWorker" protocol="tcp" />
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);
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"]);
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.
Enterprises have been using both Big Data and virtualization for years. Until recently, however, most enterprises have not combined the two. Big Data's demands for higher levels of performance, the ability to control quality-of-service (QoS), and the ability to adhere to SLAs have kept it on bare metal, apart from the modern data center cloud. With recent technology innovations, we've seen the advantages of bare metal erode to such a degree that the enhanced flexibility and reduced costs that cl...
Oct. 28, 2016 12:00 AM EDT Reads: 625
SYS-CON Events announced today that Niagara Networks 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. Niagara Networks offers the highest port-density systems, and the most complete Next-Generation Network Visibility systems including Network Packet Brokers, Bypass Switches, and Network TAPs.
Oct. 28, 2016 12:00 AM EDT Reads: 1,449
In his session at Cloud Expo, Robert Cohen, an economist and senior fellow at the Economic Strategy Institute, will provide economic scenarios that describe how the rapid adoption of software-defined everything including cloud services, SDDC and open networking will change GDP, industry growth, productivity and jobs. This session will also include a drill down for several industries such as finance, social media, cloud service providers and pharmaceuticals.
Oct. 28, 2016 12:00 AM EDT Reads: 2,144
Everyone knows that truly innovative companies learn as they go along, pushing boundaries in response to market changes and demands. What's more of a mystery is how to balance innovation on a fresh platform built from scratch with the legacy tech stack, product suite and customers that continue to serve as the business' foundation. In his General Session at 19th Cloud Expo, Michael Chambliss, Head of Engineering at ReadyTalk, will discuss why and how ReadyTalk diverted from healthy revenue an...
Oct. 27, 2016 10:30 PM EDT Reads: 3,082
SYS-CON Events announced today that Transparent Cloud Computing (T-Cloud) Consortium 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. The Transparent Cloud Computing Consortium (T-Cloud Consortium) will conduct research activities into changes in the computing model as a result of collaboration between "device" and "cloud" and the creation of new value and markets through organic data proces...
Oct. 27, 2016 10:30 PM EDT Reads: 1,508
Intelligent machines are here. Robots, self-driving cars, drones, bots and many IoT devices are becoming smarter with Machine Learning. In her session at @ThingsExpo, Sudha Jamthe, CEO of IoTDisruptions.com, will discuss the next wave of business disruption at the junction of IoT and AI, impacting many industries and set to change our lives, work and world as we know it.
Oct. 27, 2016 10:30 PM EDT Reads: 541
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
Oct. 27, 2016 10:30 PM EDT Reads: 9,800
In today's uber-connected, consumer-centric, cloud-enabled, insights-driven, multi-device, global world, the focus of solutions has shifted from the product that is sold to the person who is buying the product or service. Enterprises have rebranded their business around the consumers of their products. The buyer is the person and the focus is not on the offering. The person is connected through multiple devices, wearables, at home, on the road, and in multiple locations, sometimes simultaneously...
Oct. 27, 2016 10:30 PM EDT Reads: 3,834
Established in 1998, Calsoft is a leading software product engineering Services Company specializing in Storage, Networking, Virtualization and Cloud business verticals. Calsoft provides End-to-End Product Development, Quality Assurance Sustenance, Solution Engineering and Professional Services expertise to assist customers in achieving their product development and business goals. The company's deep domain knowledge of Storage, Virtualization, Networking and Cloud verticals helps in delivering ...
Oct. 27, 2016 10:15 PM EDT Reads: 1,162
In the 21st century, security on the Internet has become one of the most important issues. We hear more and more about cyber-attacks on the websites of large corporations, banks and even small businesses. When online we’re concerned not only for our own safety but also our privacy. We have to know that hackers usually start their preparation by investigating the private information of admins – the habits, interests, visited websites and so on. On the other hand, our own security is in danger bec...
Oct. 27, 2016 10:15 PM EDT Reads: 677
SYS-CON Events announced today that Hitrons 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. Hitrons Solutions Inc. is distributor in the North American market for unique products and services of small and medium-size businesses, including cloud services and solutions, SEO marketing platforms, and mobile applications.
Oct. 27, 2016 10:00 PM EDT Reads: 2,110
OnProcess Technology has announced it will be a featured speaker at @ThingsExpo, taking place November 1 - 3, 2016, in Santa Clara, California. Dan Gettens, OnProcess’ Chief Analytics Officer, will discuss how Internet of Things (IoT) data can be leveraged to predict product failures, improve uptime and slash costly inventory stock. @ThingsExpo is an annual gathering of IoT and cloud developers, practitioners and thought-leaders who exchange ideas and insights on topics ranging from Big Data in...
Oct. 27, 2016 09:45 PM EDT Reads: 537
As companies adopt the cloud-to-streamline workflow, deployment hasn’t been very seamless because of IT concerns surrounding security risks. The cloud offers many benefits, but protecting and securing information can be tricky across multiple cloud providers and remains IT’s overall responsibility. In his session at 19th Cloud Expo, Simon Bain, CEO of SearchYourCloud, will address security compliance issues associated with cloud applications and how document-level encryption is critical for sup...
Oct. 27, 2016 09:15 PM EDT Reads: 373
More and more companies are looking to microservices as an architectural pattern for breaking apart applications into more manageable pieces so that agile teams can deliver new features quicker and more effectively. What this pattern has done more than anything to date is spark organizational transformations, setting the foundation for future application development. In practice, however, there are a number of considerations to make that go beyond simply “build, ship, and run,” which changes ho...
Oct. 27, 2016 09:00 PM EDT Reads: 3,703
SYS-CON Events announced today that Impiger Technologies will exhibit in Booth #109 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. Impiger Technologies is a world-class, enterprise software product engineering company specializing in Mobile Application Development, Cloud Applications, Microsoft Technology Solutions, Web Technology and Telecom Services. Impiger Technologies helps enterprises improve busi...
Oct. 27, 2016 08:45 PM EDT Reads: 318
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...
Oct. 27, 2016 07:45 PM EDT Reads: 1,463
The explosion of new web/cloud/IoT-based applications and the data they generate are transforming our world right before our eyes. In this rush to adopt these new technologies, organizations are often ignoring fundamental questions concerning who owns the data and failing to ask for permission to conduct invasive surveillance of their customers. Organizations that are not transparent about how their systems gather data telemetry without offering shared data ownership risk product rejection, regu...
Oct. 27, 2016 07:15 PM EDT Reads: 314
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 ...
Oct. 27, 2016 05:45 PM EDT Reads: 1,192
SYS-CON Events announced today that Embotics, the cloud automation company, 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. Embotics is the cloud automation company for IT organizations and service providers that need to improve provisioning or enable self-service capabilities. With a relentless focus on delivering a premier user experience and unmatched customer support, Embotics is the fas...
Oct. 27, 2016 05:00 PM EDT Reads: 1,069
SYS-CON Events announced today that Cloudbric, a leading website security provider, 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. Cloudbric is an elite full service website protection solution specifically designed for IT novices, entrepreneurs, and small and medium businesses. First launched in 2015, Cloudbric is based on the enterprise level Web Application Firewall by Penta Security Sys...
Oct. 27, 2016 04:30 PM EDT Reads: 1,346