Welcome!

SDN Journal Authors: Elizabeth White, Liz McMillan, Pat Romanski, Stefan Bernbo, TJ Randall

Related Topics: SDN Journal, Java IoT, Microservices Expo, Containers Expo Blog, @CloudExpo, @BigDataExpo

SDN Journal: Blog Feed Post

Back to Basics: Least Connections Is Not Least Loaded

When load balancing, "least connections" does not mean "least loaded"

Performance is important, and that means it's important that our infrastructure support the need for speed. Load balancing algorithms are an integral piece of the performance equation and can both improve - or degrade - performance.

That's why it's important to understand more about the algorithms than their general selection mechanism. Understanding that round robin is basically an iterative choice, traversing a list one by one is good - but understanding what that means in terms of performance and capacity on different types of applications and application workloads is even better.

We last checked out "fastest response time" and today we're diving into "least connections" which, as stated above, does not mean "least loaded."

INTRA-APPLICATION WORKLOADS 

The industry standard "Least connections" load balancing algorithm uses the number of current connections to each application instance (member) to make its load balancing decision. The member with the least number of active connections is chosen. Pretty simple, right?

The premise of this algorithm is a general assumption that fewer connections (and thus fewer users) means less load and therefore better performance. That's operational axiom #2 at work - if performance decreases as load increases it stands to reason that performance increases as load decreases.

That would be true (and in the early days of load balancing it was true) if all intra-application workloads required the same resources. Unfortunately, that's no longer true and the result is uneven load distribution that leads to unpredictable performance fluctuations as demand increases.

Consider a simple example: a user logging into a system takes at least one if not more database queries to validate credentials and then update the system to indicate the activity. Depending on the nature of the application, other intra-application activities will require different quantities of resources. Some are RAM heavy, others CPU heavy, others file or database heavy. Furthermore, depending on the user in question, the usage pattern will vary greatly. One hundred users can be logged into the same system (requiring at a minimum ten connections) but if they're all relatively idle, the system will be lightly loaded and performing well.

Conversely, another application instance may boast only 50 connections, but all fifty users are heavily active with database queries returning large volumes of data. The system is far more heavily loaded and performance may be already beginning to suffer.

When the next request comes in, however, the load balancer using a "least connections" algorithm will choose the latter member, increasing the burden on that member and likely further degrading performance.

The premise of the least connections algorithm is that the application instance with the fewest number of connections is the least loaded. Except, it's not.

The only way to know which application instance is the least loaded is to monitor its system variables directly, gathering CPU utilization and memory and comparing it against known maximums. That generally requires either SNMP, agents, or other active monitoring mechanisms that can unduly tax the system in and of itself by virtue of consuming resources.

This is a quandary for operations, because "application workload" is simply too broad a generalization. Certainly some applications are more I/O heavy than others, still others are more CPU or connection heavy. But all applications have both a general workload profile and an intra-application workload profile. Understanding the usage patterns - the intra-application workload profile - of an application is critical to being able to determine how best to not only choose a load balancing algorithm but specify any limitations that may provide better overall performance and use of capacity during execution.

As always, being aware of the capabilities and the limitations of a given load balancing algorithm will assist in choosing one that is best able to meet the performance and availability requirements of an application (and thus the business).

Read the original blog entry...

More Stories By Lori MacVittie

Lori MacVittie is responsible for education and evangelism of application services available across F5’s entire product suite. Her role includes authorship of technical materials and participation in a number of community-based forums and industry standards organizations, among other efforts. MacVittie has extensive programming experience as an application architect, as well as network and systems development and administration expertise. Prior to joining F5, MacVittie was an award-winning Senior Technology Editor at Network Computing Magazine, where she conducted product research and evaluation focused on integration with application and network architectures, and authored articles on a variety of topics aimed at IT professionals. Her most recent area of focus included SOA-related products and architectures. She holds a B.S. in Information and Computing Science from the University of Wisconsin at Green Bay, and an M.S. in Computer Science from Nova Southeastern University.

@CloudExpo Stories
Enterprise IT has been in the era of Hybrid Cloud for some time now. But it seems most conversations about Hybrid are focused on integrating AWS, Microsoft Azure, or Google ECM into existing on-premises systems. Where is all the Private Cloud? What do technology providers need to do to make their offerings more compelling? How should enterprise IT executives and buyers define their focus, needs, and roadmap, and communicate that clearly to the providers?
The many IoT deployments around the world are busy integrating smart devices and sensors into their enterprise IT infrastructures. Yet all of this technology – and there are an amazing number of choices – is of no use without the software to gather, communicate, and analyze the new data flows. Without software, there is no IT. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, Dave McCarthy, Director of Products at Bsquare Corporation; Alan Williamson, Principal...
Video experiences should be unique and exciting! But that doesn’t mean you need to patch all the pieces yourself. Users demand rich and engaging experiences and new ways to connect with you. But creating robust video applications at scale can be complicated, time-consuming and expensive. In his session at @ThingsExpo, Zohar Babin, Vice President of Platform, Ecosystem and Community at Kaltura, discussed how VPaaS enables you to move fast, creating scalable video experiences that reach your aud...
Get deep visibility into the performance of your databases and expert advice for performance optimization and tuning. You can't get application performance without database performance. Give everyone on the team a comprehensive view of how every aspect of the system affects performance across SQL database operations, host server and OS, virtualization resources and storage I/O. Quickly find bottlenecks and troubleshoot complex problems.
President Obama recently announced the launch of a new national awareness campaign to "encourage more Americans to move beyond passwords – adding an extra layer of security like a fingerprint or codes sent to your cellphone." The shift from single passwords to multi-factor authentication couldn’t be timelier or more strategic. This session will focus on why passwords alone are no longer effective, and why the time to act is now. In his session at 19th Cloud Expo, Chris Webber, security strateg...
Amazon has gradually rolled out parts of its IoT offerings in the last year, but these are just the tip of the iceberg. In addition to optimizing their back-end AWS offerings, Amazon is laying the ground work to be a major force in IoT – especially in the connected home and office. Amazon is extending its reach by building on its dominant Cloud IoT platform, its Dash Button strategy, recently announced Replenishment Services, the Echo/Alexa voice recognition control platform, the 6-7 strategic...
"We are an all-flash array storage provider but our focus has been on VM-aware storage specifically for virtualized applications," stated Dhiraj Sehgal of Tintri in this SYS-CON.tv interview at 19th Cloud Expo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
"We are a leader in the market space called network visibility solutions - it enables monitoring tools and Big Data analysis to access the data and be able to see the performance," explained Shay Morag, VP of Sales and Marketing at Niagara Networks, in this SYS-CON.tv interview at 19th Cloud Expo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Whether your IoT service is connecting cars, homes, appliances, wearable, cameras or other devices, one question hangs in the balance – how do you actually make money from this service? The ability to turn your IoT service into profit requires the ability to create a monetization strategy that is flexible, scalable and working for you in real-time. It must be a transparent, smoothly implemented strategy that all stakeholders – from customers to the board – will be able to understand and comprehe...
More and more brands have jumped on the IoT bandwagon. We have an excess of wearables – activity trackers, smartwatches, smart glasses and sneakers, and more that track seemingly endless datapoints. However, most consumers have no idea what “IoT” means. Creating more wearables that track data shouldn't be the aim of brands; delivering meaningful, tangible relevance to their users should be. We're in a period in which the IoT pendulum is still swinging. Initially, it swung toward "smart for smart...
Complete Internet of Things (IoT) embedded device security is not just about the device but involves the entire product’s identity, data and control integrity, and services traversing the cloud. A device can no longer be looked at as an island; it is a part of a system. In fact, given the cross-domain interactions enabled by IoT it could be a part of many systems. Also, depending on where the device is deployed, for example, in the office building versus a factory floor or oil field, security ha...
An IoT product’s log files speak volumes about what’s happening with your products in the field, pinpointing current and potential issues, and enabling you to predict failures and save millions of dollars in inventory. But until recently, no one knew how to listen. In his session at @ThingsExpo, Dan Gettens, Chief Research Officer at OnProcess, discussed recent research by Massachusetts Institute of Technology and OnProcess Technology, where MIT created a new, breakthrough analytics model for s...
In IT, we sometimes coin terms for things before we know exactly what they are and how they’ll be used. The resulting terms may capture a common set of aspirations and goals – as “cloud” did broadly for on-demand, self-service, and flexible computing. But such a term can also lump together diverse and even competing practices, technologies, and priorities to the point where important distinctions are glossed over and lost.
SYS-CON Events has announced today that Roger Strukhoff has been named conference chair of Cloud Expo and @ThingsExpo 2017 New York. The 20th Cloud Expo and 7th @ThingsExpo will take place on June 6-8, 2017, at the Javits Center in New York City, NY. "The Internet of Things brings trillions of dollars of opportunity to developers and enterprise IT, no matter how you measure it," stated Roger Strukhoff. "More importantly, it leverages the power of devices and the Internet to enable us all to im...
"We are the public cloud providers. We are currently providing 50% of the resources they need for doing e-commerce business in China and we are hosting about 60% of mobile gaming in China," explained Yi Zheng, CPO and VP of Engineering at CDS Global Cloud, in this SYS-CON.tv interview at 19th Cloud Expo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
"We are a custom software development, engineering firm. We specialize in cloud applications from helping customers that have on-premise applications migrating to the cloud, to helping customers design brand new apps in the cloud. And we specialize in mobile apps," explained Peter Di Stefano, Vice President of Marketing at Impiger Technologies, in this SYS-CON.tv interview at 19th Cloud Expo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
When it comes to cloud computing, the ability to turn massive amounts of compute cores on and off on demand sounds attractive to IT staff, who need to manage peaks and valleys in user activity. With cloud bursting, the majority of the data can stay on premises while tapping into compute from public cloud providers, reducing risk and minimizing need to move large files. In his session at 18th Cloud Expo, Scott Jeschonek, Director of Product Management at Avere Systems, discussed the IT and busin...
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at 20th Cloud Expo, Ed Featherston, director/senior enterprise architect at Collaborative Consulting, will discuss the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
What happens when the different parts of a vehicle become smarter than the vehicle itself? As we move toward the era of smart everything, hundreds of entities in a vehicle that communicate with each other, the vehicle and external systems create a need for identity orchestration so that all entities work as a conglomerate. Much like an orchestra without a conductor, without the ability to secure, control, and connect the link between a vehicle’s head unit, devices, and systems and to manage the ...
Financial Technology has become a topic of intense interest throughout the cloud developer and enterprise IT communities. Accordingly, attendees at the upcoming 20th Cloud Expo at the Javits Center in New York, June 6-8, 2017, will find fresh new content in a new track called FinTech.