|By Steve Weisfeldt||
|February 11, 2013 05:00 PM EST||
Load testing, perhaps more than any other form of testing, is one of those activities that you either choose to do well or risk a result that leaves you worse off than not doing it at all. Half-hearted attempts at load testing yield "results," but too often those results are inaccurate, leading to a false sense of security for anyone who trusts them. This, in turn, leads to the release of applications that are not adequately tested and that experience performance problems soon after entering production.
I was reminded of this not long ago, when I worked with a customer who related an experience that may sound familiar to many of you. This customer was a test engineer for a bank that had recently merged with another bank, effectively doubling their customer base. He was part of a team responsible for load testing a new web application that would serve customers from both of the original banks. Before the application was rolled out, they performed load tests and confirmed that the application could handle the expected number of users with acceptable response times. When the system went live, however, it was slow as molasses - even under user loads less than what the team had tested.
The problem, as you may have guessed, was that the team had not accurately modeled the load. The virtual users used in the testing were a homogenous group that interacted with the system in roughly the same way, from roughly the same geographic locations, at the same network speed. In reality, the customers who came from Bank A tended to perform certain transactions much more frequently than those who came from Bank B. Most of Bank B's customers lived in a different part of the country than those from Bank A. More important, customers from both banks were accessing the application at widely differing connection speeds across a range of browsers. None of these factors were modeled accurately in the load tests the team had performed. In some cases it was because the team simply had not considered them, in others it was because the load testing tool they were using provided no way to handle these differences. In either case, the result was the same; the team had given the "go live" signal to an application that was not ready, basing their decision on inaccurate load test results.
Too often, organizations take a short cut to load testing. They are focused on a single number: how many concurrent users their application will support. As a result they put little effort into script development, and they end up with an unrealistic test - one of little value. I encourage all load testers to think beyond the concurrent users metric and take a closer look at other factors that go into creating a realistic load that will yield more accurate results, including:
- Modeling user activity
- Modeling different connection speeds
- Modeling different browsers and mobile devices
- Modeling geographically distributed users
Parameterizing Scripts to Better Model User Activity
Scripts that simply record a typical user's interaction with a web application and then play it back are not going to yield accurate performance data. As an example, a script that emulates a user logging into a site, searching for a product, placing it in the cart, and checking out does little to test the performance of other user activities such as checking product reviews, accessing detailed specifications, or comparing products.
More important, if the script always logs in as the same user and orders the same product, caching effects will often skew the performance measurements, making response times shorter than they would be under a real-world load. Caching on the web server, application server, and database server all come into play, compounding any caching that is done on the client side.
To minimize caching and similar effects, scripts must be parameterized. In my example above, the script would play back different users searching for different products, and purchasing them via different methods. Ideally the script would use randomization or data customization to fill in every user editable or selectable element on each form of the web application. This script parameterization, combined with creating multiple scripts to address a variety of user interactions, produces a much more realistic user load, and it's a good idea to have a load testing tool that simplifies these tasks.
Generating a Load with a Mixture of Connection Speeds and Network Characteristics
Many testing teams use the fastest available network connections when load testing a server. The belief is that if the application performs well under those connections, it will be guaranteed to work well in production when many real-world users will have slower connections. This is a faulty assumption that leads to performance problems when the application is subjected to real-world users accessing it at a variety of network bandwidths.
Testing with only high-speed connections can mask performance problems that occur only when lower speed connections are used. Slower data speeds will require connections to the server to stay open longer, and eventually the server may reach its limit for the maximum number of open connections.
Of course, testing with only low-speed connections is equally problematic. What's needed is a reasonable mixture of virtual users accessing the server at connection speeds representative of everything from 56K modems for dial-up users to T3 lines.
With more and more users accessing the web via mobile devices, it makes sense to include 3G and 4G connection rates in the mix as well. It's also important to take into account disparities in signal strength that can cause packet loss and increased network latency. Built-in support for incorporating these factors in performance testing is increasingly important, particularly for web applications that serve a high percentage of mobile users.
Emulating Different Browsers and Native Mobile Apps
Interestingly enough (and often surprising to some), not all browsers support the same number of concurrent HTTP connections. This obviously needs to be thought of as well - if a load test models the entire user population accessing a web application with a single browser that supports four connections per server, it neglects the effects of browsers that use twice that number.
This leads to a situation similar to the one that arises with inaccurate modeling of connection speeds - with more concurrent connections, it is not unusual to see slowdowns as a server reaches its limit for simultaneous connections. To minimize these effects, load tests should apply a variety of browser profiles during playback, so that the tests identify the traffic as originating from a realistic mixture of different browsers, including mobile browsers.
Mobile devices, in fact, present a new set of challenges for load testers (see Best Practices for Load Testing Mobile Applications, Part 1 and Best Practices for Load Testing Mobile Applications, Part 2), aside from the network connection issues I've already covered. Many companies now have a separate mobile version of their site, with content tailored specifically for mobile users. Again, to perform a valid load test on such sites, a test engineer must be able to override the browser identification during playback so that the virtual user appears to be using a mobile browser.
What about native mobile applications? There is no browser involved, so you'll need a testing solution that can record, parameterize, and play back the network traffic originating from the mobile device. For some cases this can be done via a proxy, but for some apps this is not an available option. These apps may call for a tunneling approach in which the testing tool acts as a DNS server. Even if you're not facing this situation today, you may want to see if your testing tool supports this feature so you're prepared when you do need it.
Generating a Geographically Distributed Load
Unless your end-user community is accessing your application from a single location, initiating tests solely from inside your datacenter is unlikely to represent a realistic load. Such tests fail to take into account the effects of third-party servers and content delivery networks that may sit between your users and your web application.
Using the cloud to generate load as part of your testing can better model a geographically distributed user base, one that may include users from around the world, enabling test engineers to generate realistic, large-scale tests across multiple regions. Cloud testing complements internal, lab-based tests and ideally test scripts from one domain are reused in the other. With separate performance metrics for each geographic region in hand, engineers can see where performance issues are likely to arise on a region-by-region basis.
If users are accessing your web site from all over the world, load testing from the cloud helps you model that reality. When this capability is combined with tests that incorporate parameterized scripts, browser differences, support for mobile apps, and a variety of connection speeds and network effects, you can trust the accuracy of your test results.
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportuni...
Jul. 23, 2016 10:15 PM EDT Reads: 2,400
From wearable activity trackers to fantasy e-sports, data and technology are transforming the way athletes train for the game and fans engage with their teams. In his session at @ThingsExpo, will present key data findings from leading sports organizations San Francisco 49ers, Orlando Magic NBA team. By utilizing data analytics these sports orgs have recognized new revenue streams, doubled its fan base and streamlined costs at its stadiums. John Paul is the CEO and Founder of VenueNext. Prior ...
Jul. 23, 2016 09:30 PM EDT Reads: 1,936
A critical component of any IoT project is what to do with all the data being generated. This data needs to be captured, processed, structured, and stored in a way to facilitate different kinds of queries. Traditional data warehouse and analytical systems are mature technologies that can be used to handle certain kinds of queries, but they are not always well suited to many problems, particularly when there is a need for real-time insights.
Jul. 23, 2016 08:45 PM EDT Reads: 1,637
CenturyLink has announced that application server solutions from GENBAND are now available as part of CenturyLink’s Networx contracts. The General Services Administration (GSA)’s Networx program includes the largest telecommunications contract vehicles ever awarded by the federal government. CenturyLink recently secured an extension through spring 2020 of its offerings available to federal government agencies via GSA’s Networx Universal and Enterprise contracts. GENBAND’s EXPERiUS™ Application...
Jul. 23, 2016 08:30 PM EDT Reads: 1,764
"My role is working with customers, helping them go through this digital transformation. I spend a lot of time talking to banks, big industries, manufacturers working through how they are integrating and transforming their IT platforms and moving them forward," explained William Morrish, General Manager Product Sales at Interoute, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
Jul. 23, 2016 08:30 PM EDT Reads: 2,010
Big Data engines are powering a lot of service businesses right now. Data is collected from users from wearable technologies, web behaviors, purchase behavior as well as several arbitrary data points we’d never think of. The demand for faster and bigger engines to crunch and serve up the data to services is growing exponentially. You see a LOT of correlation between “Cloud” and “Big Data” but on Big Data and “Hybrid,” where hybrid hosting is the sanest approach to the Big Data Infrastructure pro...
Jul. 23, 2016 08:00 PM EDT Reads: 1,777
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo Silicon Valley Call for Papers is now open.
Jul. 23, 2016 08:00 PM EDT Reads: 2,408
The IoT is changing the way enterprises conduct business. In his session at @ThingsExpo, Eric Hoffman, Vice President at EastBanc Technologies, discussed how businesses can gain an edge over competitors by empowering consumers to take control through IoT. He cited examples such as a Washington, D.C.-based sports club that leveraged IoT and the cloud to develop a comprehensive booking system. He also highlighted how IoT can revitalize and restore outdated business models, making them profitable ...
Jul. 23, 2016 07:15 PM EDT Reads: 1,863
We all know the latest numbers: Gartner, Inc. forecasts that 6.4 billion connected things will be in use worldwide in 2016, up 30 percent from last year, and will reach 20.8 billion by 2020. We're rapidly approaching a data production of 40 zettabytes a day – more than we can every physically store, and exabytes and yottabytes are just around the corner. For many that’s a good sign, as data has been proven to equal money – IF it’s ingested, integrated, and analyzed fast enough. Without real-ti...
Jul. 23, 2016 07:00 PM EDT Reads: 858
I wanted to gather all of my Internet of Things (IOT) blogs into a single blog (that I could later use with my University of San Francisco (USF) Big Data “MBA” course). However as I started to pull these blogs together, I realized that my IOT discussion lacked a vision; it lacked an end point towards which an organization could drive their IOT envisioning, proof of value, app dev, data engineering and data science efforts. And I think that the IOT end point is really quite simple…
Jul. 23, 2016 06:15 PM EDT Reads: 785
With 15% of enterprises adopting a hybrid IT strategy, you need to set a plan to integrate hybrid cloud throughout your infrastructure. In his session at 18th Cloud Expo, Steven Dreher, Director of Solutions Architecture at Green House Data, discussed how to plan for shifting resource requirements, overcome challenges, and implement hybrid IT alongside your existing data center assets. Highlights included anticipating workload, cost and resource calculations, integrating services on both sides...
Jul. 23, 2016 06:00 PM EDT Reads: 1,878
"We are a well-established player in the application life cycle management market and we also have a very strong version control product," stated Flint Brenton, CEO of CollabNet,, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
Jul. 23, 2016 05:30 PM EDT Reads: 1,713
The IoT has the potential to create a renaissance of manufacturing in the US and elsewhere. In his session at 18th Cloud Expo, Florent Solt, CTO and chief architect of Netvibes, discussed how the expected exponential increase in the amount of data that will be processed, transported, stored, and accessed means there will be a huge demand for smart technologies to deliver it. Florent Solt is the CTO and chief architect of Netvibes. Prior to joining Netvibes in 2007, he co-founded Rift Technologi...
Jul. 23, 2016 05:00 PM EDT Reads: 934
Unless your company can spend a lot of money on new technology, re-engineering your environment and hiring a comprehensive cybersecurity team, you will most likely move to the cloud or seek external service partnerships. In his session at 18th Cloud Expo, Darren Guccione, CEO of Keeper Security, revealed what you need to know when it comes to encryption in the cloud.
Jul. 23, 2016 04:00 PM EDT Reads: 2,301
We're entering the post-smartphone era, where wearable gadgets from watches and fitness bands to glasses and health aids will power the next technological revolution. With mass adoption of wearable devices comes a new data ecosystem that must be protected. Wearables open new pathways that facilitate the tracking, sharing and storing of consumers’ personal health, location and daily activity data. Consumers have some idea of the data these devices capture, but most don’t realize how revealing and...
Jul. 23, 2016 04:00 PM EDT Reads: 1,974
What are the successful IoT innovations from emerging markets? What are the unique challenges and opportunities from these markets? How did the constraints in connectivity among others lead to groundbreaking insights? In her session at @ThingsExpo, Carmen Feliciano, a Principal at AMDG, will answer all these questions and share how you can apply IoT best practices and frameworks from the emerging markets to your own business.
Jul. 23, 2016 03:45 PM EDT Reads: 1,505
Basho Technologies has announced the latest release of Basho Riak TS, version 1.3. Riak TS is an enterprise-grade NoSQL database optimized for Internet of Things (IoT). The open source version enables developers to download the software for free and use it in production as well as make contributions to the code and develop applications around Riak TS. Enhancements to Riak TS make it quick, easy and cost-effective to spin up an instance to test new ideas and build IoT applications. In addition to...
Jul. 23, 2016 03:30 PM EDT Reads: 1,838
You think you know what’s in your data. But do you? Most organizations are now aware of the business intelligence represented by their data. Data science stands to take this to a level you never thought of – literally. The techniques of data science, when used with the capabilities of Big Data technologies, can make connections you had not yet imagined, helping you discover new insights and ask new questions of your data. In his session at @ThingsExpo, Sarbjit Sarkaria, data science team lead ...
Jul. 23, 2016 03:15 PM EDT Reads: 816
Extracting business value from Internet of Things (IoT) data doesn’t happen overnight. There are several requirements that must be satisfied, including IoT device enablement, data analysis, real-time detection of complex events and automated orchestration of actions. Unfortunately, too many companies fall short in achieving their business goals by implementing incomplete solutions or not focusing on tangible use cases. In his general session at @ThingsExpo, Dave McCarthy, Director of Products...
Jul. 23, 2016 03:00 PM EDT Reads: 1,652
Ask someone to architect an Internet of Things (IoT) solution and you are guaranteed to see a reference to the cloud. This would lead you to believe that IoT requires the cloud to exist. However, there are many IoT use cases where the cloud is not feasible or desirable. In his session at @ThingsExpo, Dave McCarthy, Director of Products at Bsquare Corporation, will discuss the strategies that exist to extend intelligence directly to IoT devices and sensors, freeing them from the constraints of ...
Jul. 23, 2016 02:30 PM EDT Reads: 1,702