Welcome!

SOA & WOA Authors: Craig Ferril, Peter Silva, Carmen Gonzalez, Liz McMillan, Trevor Parsons

Related Topics: Java, SOA & WOA, ColdFusion, .NET, AJAX & REA

Java: Article

Load Testing in Clustered Environments

Clustered Environments: Load Testing for Architectural Validation (P.S. Don’t Extrapolate!)

Load and performance testing web applications will allow you to determine whether or not your deployment will require a clustered environment. When the test results show that the current throughput is restricted by the capacity of the server but target workloads are not yet met, this is a situation where you can achieve higher scalability by implementing clusters to your environment. Clustering achieves higher scalability by introducing more servers or nodes to expand the capacity of the environment. Obviously, the benefits of adding hardware include higher capacity, reliability, availability, and scalability. But also consider that clustering also adds complexity to your deployment by requiring added maintenance and an increased need for deployment/upgrade automation. To ensure quality of the environment you must always validate your clustered environment and prove out the increased scalability. Use a methodical performance testing approach. Don't try to extrapolate! It's not as easy as "3 nodes in a cluster will support 3x the workload."

Why Cluster?
An efficiently tuned deployment will, in turn, display an efficient use of server resources (memory, CPU, i/o, etc). Using a cluster increases the number of servers and distributes the workload amongst several servers. This even distribution of the workload can dramatically increase scalability. Not only can this improve the end user experience by reaching higher workloads with predictable response times but it can increase the reliability and stability of the deployment. The cluster acts as a single server so the loss or shutdown of any of the nodes in the cluster will not result in loss of sessions or application data. In the end, the user experience is less frequently interrupted and isn't affected by a single maxed out server or a loss of a server.

Tuning Tips
When performance or load testing your application uncovers a clear need to introduce clusters or farms to support the target workload, you will want to take into account the following considerations: First you should configure the cluster efficiently for internal maintenance such as data synchronization and heartbeat communications. User sessions which live in memory are more quickly failed over to another node in the cluster instead of persisting them to the database. However, writing the sessions to disk is more permanent which may have its own advantages. Make sure you have tested the performance prices for data synchronization and heartbeat communications. The goal is to configure the cluster to increase scalability with as little overhead as possible.

Load Balancers
Load balancers are generally placed out in front of the clusters. These load balancers can be a software solution or a hardware solution. Their job is to distribute the load evenly to the nodes in the cluster. Just as important, LB's reroute traffic when one node of the cluster goes down. This allows for the "transparency" of several servers acting as one. There are several more mature algorithms for distribution than traditional "round robins." Smarter LB's takes into account the CPU and resource usage and overall load of each server and their job is to direct the request to the least loaded server. The number of active users doesn't always equate to more resources being actively used, rather it depends on the types of transactions being executed - lightweight vs. expensive transactions. Smart LB's will detect workload and direct incoming traffic based on resource usage. Often LB's will use sticky sessions based on the client's cookie and/or IP address to route subsequent requests to the same node of cluster where the user session lives. Whenload testing these types of environments, it's a requirement to have a load tool which supports IP Spoofing. This is used to generate the load of many virtual users using multiple IP addresses all from a single machine. Otherwise, the total load would go to a single cluster node.

Types of Clustering
Clustering can be achieved using a few common techniques. Vertical clustering adds capacity to the deployment by installing multiple nodes of a cluster on a single machine. With this approach you must take into consideration the physical limitations of that machine (CPU, memory, i/o) and be careful not over utilize resources; otherwise adding more nodes becomes pointless due to saturation. Horizontal clusters refer to deploying more physical machines. With this approach, each physical machine can run one or more of the nodes of the cluster. Cloud bursting is a way of having a node both within the LAN and a node in the Cloud to be turned "on" during high volume usage or be strategically placed in different geographical locations. The appropriate technique really depends on the specifics of your environment. If you need more capacity and you have beefy infrastructure servers but do not have enough web servers or app servers to fully utilize the underlying hardware, choose the vertical clustering approach by adding more nodes to the same machine. On the other hand, if more physical resources are needed to handle the workload, then build out a horizontal cluster by adding more hardware and deploying more nodes.

How to Load Test a Cluster?
It's important to take a methodical approach to load testing a clustered environment. Load patterns such as ramping tests allow you to identify the current capacity as well as increased scalability as you add more nodes to the cluster. Remember that doubling the number of nodes in a cluster does not equate to doubling its capacity. Many components impact its performance gain such as the communications between the nodes used to just make the cluster work properly. The resource cost increases dramatically with the number of nodes. Capacity is relative and is dependent on myriad other components within the infrastructure. For example, adding another node to the cluster may give the application layer 2x the throughput (although this is not really possible due to "housekeeping" from internal administration overhead to maintain that cluster), but let's say the single webserver out front is already using all its worker threads, then requests will be queued while waiting for a thread to become available and overall throughput will not increase. Only through the analysis of load test results will you completely understand the increased scalability effects of a cluster. Consider another scenario: You have identified a need for building out a cluster of application servers, however you deploy too many nodes resulting in a backlog of requests on the shared database. Performance and load testing will uncover this vulnerability and many other potential scenarios that could otherwise go undetected. Having a comparison analysis feature built right into the load tool will allow you to run tests back to back, after turning on/off nodes in the cluster, and quickly visualize the differences. Also, having the tool with a built-in cloud load generation feature will save time and money setting up and maintaining the performance architecture environment, especially for high load tests.

The Right Approach?
Adding clustering to a deployment allows a web application to achieve higher workloads and gives the advantage of higher availability. However, you must conduct performance tests in order to build out an efficient cluster which meets your goals. Don't forget to weigh the benefits vs. added maintenance complexity/cost. Clusters require a high level of expertise to implement and maintain so they aren't the best solution in every situation. Make sure all moving parts are documented and insist on a complete architectural diagram for future systems administrators (diagrams to include hierarchical transaction pathways as well as location of each node in the cluster including the admin consoles). In the end it's all about delivering the best possible end user experience and in many cases clustering is an excellent solution for increasing scalability of your web deployments.

More Stories By Rebecca Clinard

Rebecca Clinard is a Senior Performance Engineer at Neotys, a provider of load testing software for Web applications. Previously, she worked as a web application performance engineer for Bowstreet, Fidelity Investments, Bottomline Technologies and Timberland companies, industries spanning retail, financial services, insurance and manufacturing. Her expertise lies in creating realistic load tests and performance tuning multi-tier deployments. She has been orchestrating and conducting performance tests since 2001. Clinard graduated from University of New Hampshire with a BS and also holds a UNIX Certificate from Worcester Polytechnic Institute.

@ThingsExpo Stories
SYS-CON Events announced today that Windstream, a leading provider of advanced network and cloud communications, has been named “Silver Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. Windstream (Nasdaq: WIN), a FORTUNE 500 and S&P 500 company, is a leading provider of advanced network communications, including cloud computing and managed services, to businesses nationwide. The company also offers broadband, phone and digital TV services to consumers primarily in rural areas.
"There is a natural synchronization between the business models, the IoT is there to support ,” explained Brendan O'Brien, Co-founder and Chief Architect of Aria Systems, in this SYS-CON.tv interview at the 15th International Cloud Expo®, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
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), moderated by Ashar Baig, Research Director, Cloud, at Gigaom Research, Nate Gordon, Director of T...
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 hardware to software, or as we like to say, it’s an Internet of many different things. The difference ...

ARMONK, N.Y., Nov. 20, 2014 /PRNewswire/ --  IBM (NYSE: IBM) today announced that it is bringing a greater level of control, security and flexibility to cloud-based application development and delivery with a single-tenant version of Bluemix, IBM's platform-as-a-service. The new platform enables developers to build ap...

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.
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 assessments, including a decade of leading incident response and digital forensics. He is co-author of t...
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 Architect for the Internet of Things and Intelligent Systems at Red Hat, described how to revolutioniz...
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 real benefits to focus on, how to understand the requirements of a successful solution, the flow of ...
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, and physical persons. In the IoT vision, every new "thing" - sensor, actuator, data source, data con...
"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.
Focused on this fast-growing market’s needs, Vitesse Semiconductor Corporation (Nasdaq: VTSS), a leading provider of IC solutions to advance "Ethernet Everywhere" in Carrier, Enterprise and Internet of Things (IoT) networks, introduced its IStaX™ software (VSC6815SDK), a robust protocol stack to simplify deployment and management of Industrial-IoT network applications such as Industrial Ethernet switching, surveillance, video distribution, LCD signage, intelligent sensors, and metering equipment. Leveraging technologies proven in the Carrier and Enterprise markets, IStaX is designed to work ac...
C-Labs LLC, a leading provider of remote and mobile access for the Internet of Things (IoT), announced the appointment of John Traynor to the position of chief operating officer. Previously a strategic advisor to the firm, Mr. Traynor will now oversee sales, marketing, finance, and operations. Mr. Traynor is based out of the C-Labs office in Redmond, Washington. He reports to Chris Muench, Chief Executive Officer. Mr. Traynor brings valuable business leadership and technology industry expertise to C-Labs. With over 30 years' experience in the high-tech sector, John Traynor has held numerous...
Bit6 today issued a challenge to the technology community implementing Web Real Time Communication (WebRTC). To leap beyond WebRTC’s significant limitations and fully leverage its underlying value to accelerate innovation, application developers need to consider the entire communications ecosystem.
The 3rd International @ThingsExpo, 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 Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - computers, smartphones, tablets, and sensors - connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades.
The Internet of Things is not new. Historically, smart businesses have used its basic concept of leveraging data to drive better decision making and have capitalized on those insights to realize additional revenue opportunities. So, what has changed to make the Internet of Things one of the hottest topics in tech? In his session at @ThingsExpo, Chris Gray, Director, Embedded and Internet of Things, discussed the underlying factors that are driving the economics of intelligent systems. Discover how hardware commoditization, the ubiquitous nature of connectivity, and the emergence of Big Data a...
Almost everyone sees the potential of Internet of Things but how can businesses truly unlock that potential. The key will be in the ability to discover business insight in the midst of an ocean of Big Data generated from billions of embedded devices via Systems of Discover. Businesses will also need to ensure that they can sustain that insight by leveraging the cloud for global reach, scale and elasticity.
SYS-CON Events announced today that IDenticard will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. IDenticard™ is the security division of Brady Corp (NYSE: BRC), a $1.5 billion manufacturer of identification products. We have small-company values with the strength and stability of a major corporation. IDenticard offers local sales, support and service to our customers across the United States and Canada. Our partner network encompasses some 300 of the world's leading systems integrators and security s...
IoT is still a vague buzzword for many people. In his session at @ThingsExpo, Mike Kavis, Vice President & Principal Cloud Architect at Cloud Technology Partners, discussed the business value of IoT that goes far beyond the general public's perception that IoT is all about wearables and home consumer services. He also discussed how IoT is perceived by investors and how venture capitalist access this space. Other topics discussed were barriers to success, what is new, what is old, and what the future may hold. Mike Kavis is Vice President & Principal Cloud Architect at Cloud Technology Pa...
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. The next @ThingsExpo will take place November 4-6, 2014, at the Santa Clara Convention Center, in Santa Clara, California. Since its launch in 2008, Cloud Expo TV commercials have been aired and CNBC, Fox News Network, and Bloomberg TV. Please enjoy our 2014 commercial.