|By Mario Meir-Huber||
|May 20, 2012 02:00 PM EDT||
Infrastructure as a Service and Platform as a Service offer us easy scaling of services. However, scaling is not as easy as it seems to be in the Cloud. If your software architecture isn't done right, your services and applications might not scale as expected, even if you add new instances. As for most distributed systems, there are a couple of guidelines you should consider. I have summed up the ones I use most often for designing distributed systems.
Design for Failure
As Moore stated, everything that can fail, will fail. So it is very clear that a distributed system will fail at a certain time, even though cloud computing providers tell us that it is very unlikely. We had some outages  in the last year of some of the major platforms, and there might be even more of them. Therefore, your application should be able to deal with an outage of your cloud provider. This can be done with different techniques such as distributing an application in more than one availability zone (which should be done anyway). Netflix has a very interesting approach to steadily test their software for errors - they have employed an army of "Chaos Monkeys" . Of course, they are not real monkeys. It is software that randomly takes down different Instances. Netflix produces errors on purpose to see how their system reacts and if it is still performing well. The question is not if there will be another outage; the question is when the next outage will be.
Design for at Least Three Running Systems
For on-premise systems, we always used to do an "N+1" Design. This still applies in the cloud. There should always be one more system available than actually necessary. In the cloud, this can easily be achieved by running your instances in different geographical locations and availability zones. In case one region fails, the other region will take over. Some platforms offer intelligent routing and can easily forward traffic to another zone if one zone is down. However, there is this "rule of three," that basically says you should have three systems available: one for me, one for the customer and one if there is a failure. This will minimize the risk of an outage significantly for you.
Design for Monitoring
We all need to know what is going on in our datacenters and on our systems. Therefore, monitoring is an important aspect for every application you build. If you want to design intelligent monitoring, I/O performance or other metrics are not the only important things. It would be best if your system could "predict" your future load - this could either be done by statistical data you have from your applications‘ history or from your applications‘ domain. If your application is on sports betting, you might have high load on during major sports events. If it is for social games, your load might be higher during the day or when the weather is bad outside. However, your system should be monitored all the time and it should tell you in case a major failure might come up.
Design for Rollback
Large systems are typically owned by different teams in your company. This means that a lot of people work on your systems and rollout happens often. Even though there should be a lot of testing involved, it will still happen that new features will affect other services of your application. To prevent from that, our application should allow an easy rollback mechanism.
Design No State
State kills. If you store states on your systems, this will make load balancing much more complicated for you. State should be eliminated wherever and whenever possible. There are several techniques to reduce or remove state in your application. Modern devices such as tablets or smartphones have sufficient performance to store state information on the client. Every service call should be independent and it shouldn‘t be necessary to have a session state on the server. All session state should be transferred to the client, as described by Roy Fielding . Architectural styles such as ROA support this idea and help you make your services stateless. I will dig into ReST and ROA in one of my upcoming articles since this is really great for distributed systems.
Design to Disable Services
It should be easy to disable services that are not performing well or influencing your system in a way that is poisoning the entire application. Therefore, it will be important to isolate each service from each other, since it should not affect the entire system's functionality. Imagine the comment function of Amazon is not working - this might be essential to make up your mind about buying a book, but it wouldn't prevent you from buying the book.
Design Different Roles
However, with distributed systems we have a lot of servers involved - and it‘s necessary not to scale a front-end or back-end server, but to scale individual services. If there is exactly one front-end system that hosts all roles and a specific service experiences high load, why would it be necessary to scale up all services, even those services that have minor load? You might improve your systems if you have them split up in different roles. As already described by Bertram Meyer  with Command Query Separation, your application should also be split in different roles. This is basically a key thing for SOA applications; however, I still see that most services are not separated. There should be more separation of concerns based on the services. Implement some kind of application role separation for your application and services to improve scaling.
There might be additional principles for distributed systems. I see this article as a rather "living" one and will extend it over the time. I would be interested is your feedback on this. What are your thoughts on distributed systems? Email me at [email protected], use the comment section here or get in touch with me via Twitter at @mario_mh
Verizon Enterprise Solutions is simplifying the cloud-purchasing experience for its clients, with the launch of Verizon Cloud Marketplace, a key foundational component of the company's robust ecosystem of enterprise-class technologies. The online storefront will initially feature pre-built cloud-based services from AppDynamics, Hitachi Data Systems, Juniper Networks, PfSense and Tervela. Available globally to enterprises using Verizon Cloud, Verizon Cloud Marketplace provides a one-stop shop fo...
Nov. 23, 2014 11:00 AM EST Reads: 1,159
Leysin American School is an exclusive, private boarding school located in Leysin, Switzerland. Leysin selected an OpenStack-powered, private cloud as a service to manage multiple applications and provide development environments for students across the institution. Seeking to meet rigid data sovereignty and data integrity requirements while offering flexible, on-demand cloud resources to users, Leysin identified OpenStack as the clear choice to round out the school's cloud strategy. Additional...
Nov. 23, 2014 08:00 AM EST Reads: 1,295
The major cloud platforms defy a simple, side-by-side analysis. Each of the major IaaS public-cloud platforms offers their own unique strengths and functionality. Options for on-site private cloud are diverse as well, and must be designed and deployed while taking existing legacy architecture and infrastructure into account. Then the reality is that most enterprises are embarking on a hybrid cloud strategy and programs. In this Power Panel at 15th Cloud Expo (http://www.CloudComputingExpo.com...
Nov. 23, 2014 07:45 AM EST Reads: 1,373
We are all here because we are sold on the transformative promise of The Cloud. But what good is all of this ephemeral, on-demand infrastructure if your usage doesn't actually improve the agility and speed of your business? How must Operations adapt in order to avoid stifling your Cloud initiative? In his session at DevOps Summit, Damon Edwards, co-founder and managing partner of the DTO Solutions, will highlight the successful organizational, process, and tooling patterns of high-performing c...
Nov. 23, 2014 02:00 AM EST Reads: 1,063
The definition of IoT is not new, in fact it’s been around for over a decade. What has changed is the public's awareness that the technology we use on a daily basis has caught up on the vision of an always on, always connected world. If you look into the details of what comprises the IoT, you’ll see that it includes everything from cloud computing, Big Data analytics, “Things,” Web communication, applications, network, storage, etc. It is essentially including everything connected online from ha...
Nov. 22, 2014 10:00 PM EST Reads: 1,176
Software-driven innovation is becoming a primary approach to how businesses create and deliver new value to customers. A survey of 400 business and IT executives by the IBM Institute for Business Value showed businesses that are more effective at software delivery are also more profitable than their peers nearly 70 percent of the time (1). DevOps provides a way for businesses to remain competitive, applying lean and agile principles to software development to speed the delivery of software that ...
Nov. 22, 2014 08:00 PM EST Reads: 1,461
Docker offers a new, lightweight approach to application portability. Applications are shipped using a common container format and managed with a high-level API. Their processes run within isolated namespaces that abstract the operating environment independently of the distribution, versions, network setup, and other details of this environment. This "containerization" has often been nicknamed "the new virtualization." But containers are more than lightweight virtual machines. Beyond their small...
Nov. 22, 2014 06:45 PM EST Reads: 1,226
The move in recent years to cloud computing services and architectures has added significant pace to the application development and deployment environment. When enterprise IT can spin up large computing instances in just minutes, developers can also design and deploy in small time frames that were unimaginable a few years ago. The consequent move toward lean, agile, and fast development leads to the need for the development and operations sides to work very closely together. Thus, DevOps become...
Nov. 22, 2014 05:45 PM EST Reads: 1,346
Cloud Expo 2014 TV commercials will feature @ThingsExpo, which was launched in June, 2014 at New York City's Javits Center as the largest 'Internet of Things' event in the world.
Nov. 22, 2014 05:30 PM EST Reads: 1,344
An entirely new security model is needed for the Internet of Things, or is it? Can we save some old and tested controls for this new and different environment? In his session at @ThingsExpo, New York's at the Javits Center, Davi Ottenheimer, EMC Senior Director of Trust, reviewed hands-on lessons with IoT devices and reveal a new risk balance you might not expect. Davi Ottenheimer, EMC Senior Director of Trust, has more than nineteen years' experience managing global security operations and asse...
Nov. 22, 2014 05:30 PM EST Reads: 1,177
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 Internet of @ThingsExpo, James Kirkland, Chief Ar...
Nov. 21, 2014 09:15 PM EST Reads: 1,292
Technology is enabling a new approach to collecting and using data. This approach, commonly referred to as the "Internet of Things" (IoT), enables businesses to use real-time data from all sorts of things including machines, devices and sensors to make better decisions, improve customer service, and lower the risk in the creation of new revenue opportunities. In his General Session at Internet of @ThingsExpo, Dave Wagstaff, Vice President and Chief Architect at BSQUARE Corporation, discuss the ...
Nov. 21, 2014 08:00 PM EST Reads: 1,362
The security devil is always in the details of the attack: the ones you've endured, the ones you prepare yourself to fend off, and the ones that, you fear, will catch you completely unaware and defenseless. The Internet of Things (IoT) is nothing if not an endless proliferation of details. It's the vision of a world in which continuous Internet connectivity and addressability is embedded into a growing range of human artifacts, into the natural world, and even into our smartphones, appliances, a...
Nov. 21, 2014 08:00 PM EST Reads: 1,311
"BSQUARE is in the business of selling software solutions for smart connected devices. It's obvious that IoT has moved from being a technology to being a fundamental part of business, and in the last 18 months people have said let's figure out how to do it and let's put some focus on it, " explained Dave Wagstaff, VP & Chief Architect, at BSQUARE Corporation, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Nov. 21, 2014 07:00 PM EST Reads: 1,235
The 4th International DevOps Summit, co-located with16th International Cloud Expo – being held June 9-11, 2015, at the Javits Center in New York City, NY – announces that its Call for Papers is now 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 large...
Nov. 21, 2014 06:45 PM EST Reads: 1,197
"Our premise is Docker is not enough. That's not a bad thing - we actually love Docker. At ActiveState all our products are based on open source technology and Docker is an up-and-coming piece of open source technology," explained Bart Copeland, President & CEO of ActiveState Software, in this SYS-CON.tv interview at DevOps Summit at Cloud Expo®, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Nov. 20, 2014 10:30 PM EST Reads: 1,294
DevOps Summit 2015 New York, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that it is now accepting Keynote Proposals. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long development cycles that produce software that is obsolete...
Nov. 20, 2014 09:00 PM EST Reads: 1,482
Infor has announced a new feature Infor CloudSuite™ Aerospace & Defense (A&D) to aid compliance with International Traffic in Arms Regulations (ITAR). The ITAR function will serve as a complementary function for new or existing Infor CloudSuite A&D customers, to facilitate compliance for Infor customers that are creating a US defense article or performing a US defense service and wish to benefit from cloud-services. The ITAR regulation serves to manage handling and access requirements for dat...
Nov. 20, 2014 07:00 PM EST Reads: 1,296
What do a firewall and a fortress have in common? They are no longer strong enough to protect the valuables housed inside. Like the walls of an old fortress, the cracks in the firewall are allowing the bad guys to slip in - unannounced and unnoticed. By the time these thieves get in, the damage is already done and the network is already compromised. Intellectual property is easily slipped out the back door leaving no trace of forced entry. If we want to reign in on these cybercriminals, it's hig...
Nov. 20, 2014 07:00 PM EST Reads: 1,163