|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.
Bert Loomis was a visionary. This general session will highlight how Bert Loomis and people like him inspire us to build great things with small inventions. In their general session at 19th Cloud Expo, Harold Hannon, Architect at IBM Bluemix, and Michael O'Neill, Strategic Business Development at Nvidia, discussed the accelerating pace of AI development and how IBM Cloud and NVIDIA are partnering to bring AI capabilities to "every day," on-demand. They also reviewed two "free infrastructure" pr...
Apr. 23, 2017 08:45 PM EDT Reads: 565
The explosion of new web/cloud/IoT-based applications and the data they generate are transforming our world right before our eyes. In this rush to adopt these new technologies, organizations are often ignoring fundamental questions concerning who owns the data and failing to ask for permission to conduct invasive surveillance of their customers. Organizations that are not transparent about how their systems gather data telemetry without offering shared data ownership risk product rejection, regu...
Apr. 23, 2017 05:30 PM EDT Reads: 825
The Internet of Things is clearly many things: data collection and analytics, wearables, Smart Grids and Smart Cities, the Industrial Internet, and more. Cool platforms like Arduino, Raspberry Pi, Intel's Galileo and Edison, and a diverse world of sensors are making the IoT a great toy box for developers in all these areas. In this Power Panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists discussed what things are the most important, which will have the most profound e...
Apr. 23, 2017 03:30 PM EDT Reads: 1,916
@ThingsExpo has been named the Most Influential ‘Smart Cities - IIoT' Account and @BigDataExpo has been named fourteenth by Right Relevance (RR), which provides curated information and intelligence on approximately 50,000 topics. In addition, Right Relevance provides an Insights offering that combines the above Topics and Influencers information with real time conversations to provide actionable intelligence with visualizations to enable decision making. The Insights service is applicable to eve...
Apr. 23, 2017 02:15 PM EDT Reads: 2,360
SYS-CON Events announced today that Grape Up will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct. 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Grape Up is a software company specializing in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market across the U.S. and Europe, Grape Up works with a variety of customers from emergi...
Apr. 23, 2017 02:00 PM EDT Reads: 1,588
SYS-CON Events announced today that Hitachi, the leading provider the Internet of Things and Digital Transformation, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Hitachi Data Systems, a wholly owned subsidiary of Hitachi, Ltd., offers an integrated portfolio of services and solutions that enable digital transformation through enhanced data management, governance, mobility and analytics. We help globa...
Apr. 23, 2017 01:45 PM EDT Reads: 1,810
In his keynote at @ThingsExpo, Chris Matthieu, Director of IoT Engineering at Citrix and co-founder and CTO of Octoblu, focused on building an IoT platform and company. He provided a behind-the-scenes look at Octoblu’s platform, business, and pivots along the way (including the Citrix acquisition of Octoblu).
Apr. 23, 2017 10:15 AM EDT Reads: 632
SYS-CON Events announced today that SoftLayer, an IBM Company, has been named “Gold Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. SoftLayer, an IBM Company, provides cloud infrastructure as a service from a growing number of data centers and network points of presence around the world. SoftLayer’s customers range from Web startups to global enterprises.
Apr. 23, 2017 09:45 AM EDT Reads: 1,839
Multiple data types are pouring into IoT deployments. Data is coming in small packages as well as enormous files and data streams of many sizes. Widespread use of mobile devices adds to the total. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists will look at the tools and environments that are being put to use in IoT deployments, as well as the team skills a modern enterprise IT shop needs to keep things running, get a handle on all this data, and deli...
Apr. 23, 2017 07:45 AM EDT Reads: 1,882
20th Cloud Expo, taking place June 6-8, 2017, at the Javits Center in New York City, NY, 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.
Apr. 23, 2017 04:45 AM EDT Reads: 2,793
SYS-CON Events announced today that Super Micro Computer, Inc., a global leader in compute, storage and networking technologies, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Supermicro (NASDAQ: SMCI), the leading innovator in high-performance, high-efficiency server technology, is a premier provider of advanced server Building Block Solutions® for Data Center, Cloud Computing, Enterprise IT, Hadoop/...
Apr. 23, 2017 04:00 AM EDT Reads: 1,755
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...
Apr. 23, 2017 03:45 AM EDT Reads: 4,727
Judith Hurwitz is president and CEO of Hurwitz & Associates, a Needham, Mass., research and consulting firm focused on emerging technology, including big data, cognitive computing and governance. She is co-author of the book Cognitive Computing and Big Data Analytics, published in 2015. Her Cloud Expo session, "What Is the Business Imperative for Cognitive Computing?" is scheduled for Wednesday, June 8, at 8:40 a.m. In it, she puts cognitive computing into perspective with its value to the busin...
Apr. 23, 2017 03:15 AM EDT Reads: 3,468
Cognitive Computing is becoming the foundation for a new generation of solutions that have the potential to transform business. Unlike traditional approaches to building solutions, a cognitive computing approach allows the data to help determine the way applications are designed. This contrasts with conventional software development that begins with defining logic based on the current way a business operates. In her session at 18th Cloud Expo, Judith S. Hurwitz, President and CEO of Hurwitz & ...
Apr. 23, 2017 01:45 AM EDT Reads: 8,703
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.
Apr. 22, 2017 11:45 PM EDT Reads: 2,108
SYS-CON Events announced today that Interoute, owner-operator of one of Europe's largest networks and a global cloud services platform, has been named “Bronze Sponsor” of SYS-CON's 20th Cloud Expo, which will take place on June 6-8, 2017 at the Javits Center in New York, New York. Interoute is the owner-operator of one of Europe's largest networks and a global cloud services platform which encompasses 12 data centers, 14 virtual data centers and 31 colocation centers, with connections to 195 add...
Apr. 22, 2017 11:15 PM EDT Reads: 1,529
The age of Digital Disruption is evolving into the next era – Digital Cohesion, an age in which applications securely self-assemble and deliver predictive services that continuously adapt to user behavior. Information from devices, sensors and applications around us will drive services seamlessly across mobile and fixed devices/infrastructure. This evolution is happening now in software defined services and secure networking. Four key drivers – Performance, Economics, Interoperability and Trust ...
Apr. 22, 2017 09:15 PM EDT Reads: 3,513
Grape Up is a software company, specialized in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market across the USA and Europe, we work with a variety of customers from emerging startups to Fortune 1000 companies.
Apr. 22, 2017 08:00 PM EDT Reads: 1,935
Cybersecurity is a critical component of software development in many industries including medical devices. However, code is not always written to be robust or secure from the unknown or the unexpected. This gap can make medical devices susceptible to cybersecurity attacks ranging from compromised personal health information to life-sustaining treatment. In his session at @ThingsExpo, Clark Fortney, Software Engineer at Battelle, will discuss how programming oversight using key methods can incre...
Apr. 22, 2017 05:45 PM EDT Reads: 3,709
Apr. 22, 2017 11:00 AM EDT Reads: 4,149