Microservices Expo Authors: Roger Strukhoff, Liz McMillan, Elizabeth White, Ruxit Blog, Derek Weeks

Related Topics: Microservices Expo

Microservices Expo: Article

SOA - Loosely Coupled...What?

For both technical and business advantages

With the advent of Web services and SOA, we've been seeking to create architectures and systems that are more loosely coupled. Loosely coupled systems provide many advantages including support for late or dynamically binding to other components while running, and can mediate the difference in the component's structure, security model, protocols, and semantics, thus abstracting volatility.

This is in contrast to compile-time or runtime binding, which requires that you bind the components at compile time or runtime (synchronous calls), respectively, and also requires that changes be designed into all components at the same time due to the dependencies. As you can imagine, this type of coupling makes testing and component changes much more difficult.

The advantages of loosely coupled architectures, as found within many SOAs, are apparent to many of us who have built architectures and systems in the past, at least from a technical perspective. However, they have business value as well.
First and foremost, a loosely coupled architecture allows you to replace components, or change components, without having to make reflective changes to other components in the architecture/systems. This means businesses can change their business systems as needed, with much more agility than if the architecture/systems were more tightly coupled. Second, developers can pick and choose the right enabling technology for the job without concerning themselves with technical dependencies, such as security models. Thus, you can build new components using J2EE, which will work and play well with other components written in Cobol or perhaps C++. Same goes for persistence layers, middleware, protocols, etc. You can mix and match to exactly meet your needs, even leverage services that may exist outside of your organization without regard to how that service was created, how it communicates, nor where it is running.

Finally, with this degree of independence, components are protected from each other and can better recover from component failure. If the SOA is designed correctly, the failure of a single component should not take down other components in the system. Thus, loose coupling creates architectures that are more resilient. Moreover, this also lends itself better to creating a failover subsystem, moving from one instance of a component to another without affecting the other components in the SOA.

It should be noted, however, that not all tight coupling is bad. Indeed, in some cases it makes sense to more tightly couple components, such as when the dependencies are critical to the design. An example would be two services that can't work apart and must function as one, and thus are better tightly coupled. You have to look at your requirement, and then determine the degree of coupling required in your architecture, and it may not always be loose coupling.

Now that we know the basic differences between a tightly and loosely coupled architecture, as well as the advantages, perhaps it's a good idea to break down loose coupling into a few basic patterns: location independence, communication independence, security independence, and instance independence.

Location independence refers to the notion that it matters not where the service exists, the other components that need to leverage the service can discovery it within a directory and leverage it through the late binding process. This comes in handy when you're leveraging services that are consistently changing physical and logical locations, especially services outside your organization that you may not own. Your risk calculation service may exist in LA on Monday and in New York on Friday, and it should make no difference to you.

Dynamic discovery is key to this, meaning that calling components can locate service information as needed, and without having to bind tightly to the service. Typically, these services are private, shared, or public service as they exist within the directory.
Communications independence means that all components can talk to each other no matter how they communicate at the interface or protocol levels. Thus, we leverage enabling standards, such as Web services, to mediate the protocol and interface difference.
Security independence refers to the concept of mediating the difference between security models in and between components. This is a bit difficult to pull off, but necessary to any SOA. To enable this pattern, you'll have to leverage a federated security system that's able to create trust between components, no matter which security model is local to the components. This has been the primary force behind the number of federated security standards that have emerged in support of a loosely coupled model and Web services.

Instance independence means that the architecture should support component-to-component communications, using both a synchronous and asynchronous model, and not require that the other component be in any particular state before receiving the request, or the message. Thus, if done right, all of the services should be able to service any requesting component, asynchronously, as well as retain and manage state no matter what the sequencing is.

The need for loosely coupled architecture within your SOA is really not the question. If you have a SOA, you should have a loosely coupled architecture, if done correctly. However, analysis and planning are also part of the mix...understanding your requirements and how each component of your architecture should leverage the other components of your architecture. With a bit of up-front work, you'll find your coupling loose and your SOA successful.

More Stories By David Linthicum

Dave Linthicum is Sr. VP at Cloud Technology Partners, and an internationally known cloud computing and SOA expert. He is a sought-after consultant, speaker, and blogger. In his career, Dave has formed or enhanced many of the ideas behind modern distributed computing including EAI, B2B Application Integration, and SOA, approaches and technologies in wide use today. In addition, he is the Editor-in-Chief of SYS-CON's Virtualization Journal.

For the last 10 years, he has focused on the technology and strategies around cloud computing, including working with several cloud computing startups. His industry experience includes tenure as CTO and CEO of several successful software and cloud computing companies, and upper-level management positions in Fortune 500 companies. In addition, he was an associate professor of computer science for eight years, and continues to lecture at major technical colleges and universities, including University of Virginia and Arizona State University. He keynotes at many leading technology conferences, and has several well-read columns and blogs. Linthicum has authored 10 books, including the ground-breaking "Enterprise Application Integration" and "B2B Application Integration." You can reach him at [email protected] Or follow him on Twitter. Or view his profile on LinkedIn.

Comments (2) View Comments

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.

Most Recent Comments
Mike 10/18/07 04:39:44 PM EDT

Can more be said about "...Thus, we leverage enabling standards, such as Web services, to mediate the protocol and interface difference...."? An example would be nice :) The service is described by WSDL, so there is no option on calling it any other way that WSDL describes. Web services by default indicate HTTP/HTTPS type of protocol....


Peter 10/15/07 06:18:10 PM EDT

I really like the tight coupled is not inheritantly evil approach;) but would really like some samples of when SOA is a VERY bad option. They exist - don't they?

Easy loosely coupled systems work great, esp for internet services. Eg. a StockQuote Service which inputs a String, and outputs a string. And it is displayed only once on user login. Web App pings the service, and displays results which are likely cached. Ez.

A much harder scenario is if every page the user traverses, every stock on the page content must be listed, along with history, graphs, news items, etc. Lets say this is a intranet service, with 5 consuming apps. Maybe much more performant with jdbc/hibernate/spring bean? What if each app is worried only about its own "set" of stocks? Might be a horrible example, but I think you get what i am asking ;)

@MicroservicesExpo Stories
As we enter the final week before the 19th International Cloud Expo | @ThingsExpo in Santa Clara, CA, it's time for me to reflect on six big topics that will be important during the show. Hybrid Cloud This general-purpose term seems to provide a comfort zone for many enterprise IT managers. It sounds reassuring to be able to work with one of the major public-cloud providers like AWS or Microsoft Azure while still maintaining an on-site presence.
19th Cloud Expo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterpri...
Without lifecycle traceability and visibility across the tool chain, stakeholders from Planning-to-Ops have limited insight and answers to who, what, when, why and how across the DevOps lifecycle. This impacts the ability to deliver high quality software at the needed velocity to drive positive business outcomes. In his general session at @DevOpsSummit at 19th Cloud Expo, Eric Robertson, General Manager at CollabNet, will discuss how customers are able to achieve a level of transparency that e...
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, will discuss how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team a...
As software becomes more and more complex, we, as software developers, have been splitting up our code into smaller and smaller components. This is also true for the environment in which we run our code: going from bare metal, to VMs to the modern-day Cloud Native world of containers, schedulers and microservices. While we have figured out how to run containerized applications in the cloud using schedulers, we've yet to come up with a good solution to bridge the gap between getting your conta...
SYS-CON Events announced today that 910Telecom 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. Housed in the classic Denver Gas & Electric Building, 910 15th St., 910Telecom is a carrier-neutral telecom hotel located in the heart of Denver. Adjacent to CenturyLink, AT&T, and Denver Main, 910Telecom offers connectivity to all major carriers, Internet service providers, Internet backbones and ...
DevOps theory promotes a culture of continuous improvement built on collaboration, empowerment, systems thinking, and feedback loops. But how do you collaborate effectively across the traditional silos? How can you make decisions without system-wide visibility? How can you see the whole system when it is spread across teams and locations? How do you close feedback loops across teams and activities delivering complex multi-tier, cloud, container, serverless, and/or API-based services?
Today every business relies on software to drive the innovation necessary for a competitive edge in the Application Economy. This is why collaboration between development and operations, or DevOps, has become IT’s number one priority. Whether you are in Dev or Ops, understanding how to implement a DevOps strategy can deliver faster development cycles, improved software quality, reduced deployment times and overall better experiences for your customers.
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 @...
This is a no-hype, pragmatic post about why I think you should consider architecting your next project the way SOA and/or microservices suggest. No matter if it’s a greenfield approach or if you’re in dire need of refactoring. Please note: considering still keeps open the option of not taking that approach. After reading this, you will have a better idea about whether building multiple small components instead of a single, large component makes sense for your project. This post assumes that you...
What do dependency resolution, situational awareness, and superheroes have in common? Meet Chris Corriere, a DevOps/Software Engineer at Autotrader, speaking on creative ways to maximize usage of all of the above. Mark Miller, Community Advocate and senior storyteller at Sonatype, caught up with Chris to learn more about what his team is up to.
@DevOpsSummit has been named the ‘Top DevOps Influencer' by iTrend. iTrend processes millions of conversations, tweets, interactions, news articles, press releases, blog posts - and extract meaning form them and analyzes mobile and desktop software platforms used to communicate, various metadata (such as geo location), and automation tools. In overall placement, @DevOpsSummit ranked as the number one ‘DevOps Influencer' followed by @CloudExpo at third, and @MicroservicesE at 24th.
JetBlue Airways uses virtual environments to reduce software development costs, centralize performance testing, and create a climate for continuous integration and real-time monitoring of mobile applications. The next BriefingsDirect Voice of the Customer performance engineering case study discussion examines how JetBlue Airways in New York uses virtual environments to reduce software development costs, centralize performance testing, and create a climate for continuous integration and real-tim...
At its core DevOps is all about collaboration. The lines of communication must be opened and it takes some effort to ensure that they stay that way. It’s easy to pay lip service to trends and talk about implementing new methodologies, but without action, real benefits cannot be realized. Success requires planning, advocates empowered to effect change, and, of course, the right tooling. To bring about a cultural shift it’s important to share challenges. In simple terms, ensuring that everyone k...
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 ...
A completely new computing platform is on the horizon. They’re called Microservers by some, ARM Servers by others, and sometimes even ARM-based Servers. No matter what you call them, Microservers will have a huge impact on the data center and on server computing in general. Although few people are familiar with Microservers today, their impact will be felt very soon. This is a new category of computing platform that is available today and is predicted to have triple-digit growth rates for some ...
As the world moves toward more DevOps and Microservices, application deployment to the cloud ought to become a lot simpler. The Microservices architecture, which is the basis of many new age distributed systems such as OpenStack, NetFlix and so on, is at the heart of Cloud Foundry - a complete developer-oriented Platform as a Service (PaaS) that is IaaS agnostic and supports vCloud, OpenStack and AWS. Serverless computing is revolutionizing computing. In his session at 19th Cloud Expo, Raghav...
So you think you are a DevOps warrior, huh? Put your money (not really, it’s free) where your metrics are and prove it by taking The Ultimate DevOps Geek Quiz Challenge, sponsored by DevOps Summit. Battle through the set of tough questions created by industry thought leaders to earn your bragging rights and win some cool prizes.
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...
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...