Load Testing Blog
Load Testing Basics: How Many Concurrent Users is Enough?
How Many Users Can Your Website Handle?
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The most common question regarding a website’s performance is not how fast the website is or how it scales, but something more fundamental:
What should the performance goal be in terms of concurrent users?
Should it be one hundred concurrent users? A thousand? Ten thousand? Does it require one server or a hundred to handle the load?
There’s a good reason for how many times this question comes up: it’s tricky and … Continue reading »
Web Performance at the Software Test Professionals Conference
Michael Czeiszperger, founder of Web Performance, Inc., will be speaking in the Performance Testing track at the upcoming Software Testing Professionals Conference March 22-24 in Nashville, TN. The talk is called Wishful Thinking and Poor Planning: Load Testing in the Real World, and is based on experience with over 590 clients. This session discusses how to deal with what actually happens in the real world of performance testing: ill-defined or non-existent customer requirements, truncated budgets and schedules, and mysterious crashes under load. This talk will outline the best ways to make sure a website meets all performance requirements despite … Continue reading »
Load Testing Back to Basics: Avoiding the KeepAliveTimeout Race Condition
You’ve recorded your test case, configured your datasets, and run your replays. You start up the load test and … you see numerous errors like this:
“The connection with the server was unexpectedly closed before starting the response.”
What’s going on? Well, one common reason for this error is a connection-related race condition between Load Tester and the web server due to the server’s configured persistent connection timeout.
Persistent connections are an HTTP mechanism for minimizing network connection overhead between the browser and the web server. If the client has the Connection request header set to Keep-Alive, and the server responds with the … Continue reading »
IE Performance Tip: avoid repeating <img> tags
This tip is more for those users who have developed a sophisticated data-crunching interface to their app. On one screen, for simplicity, the app gives a long list of data, without pagination controls being created by the user (such as a “View All” feature). To keep it pretty, each line has a visual icon or some surrounding images. Sound familiar? For example, let’s say the list is created by a testing system, indicating which tests were passed and which failed. The list may look something like:
For this example, we’ve created a few lengthy files to measure IE’s rendering performance. They … Continue reading »
Garbage Collector Performance under Load
The overwhelming majority of dynamic internet-facing applications are built on garbage collected runtimes such as Java and .NET. Garbage collection is popular because it promotes rapid application development. On the other hand, whenever a system is demonstrating unexpectedly poor performance, the garbage collector invariably surfaces as a possible suspect. Our advanced server analysis module even hooks into garbage collection performance monitoring on the .NET platform.
The reality, however, is that modern garbage collectors are very good.
Fact: Our company has been in business since 1999. In this time, no one can recall ever encountering a system with a performance problem that could … Continue reading »
Drupal: Caching and Database Scalability
Note: This is Part 4 of an ongoing series on Drupal performance and load testing. If you haven’t already, read the introduction.
Summary
We measured Drupal’s performance with respect to database size, demonstrating flat performance regardless of the size of the database. We also got some good data demonstrating Drupal’s behavior with caching.
Procedure
We re-created our previous test platform: a stock Drupal installation on an Amazon Elastic Cloud m1.large instance with both the Alternative PHP Cache (APC) and Drupal’s built-in caching capabilities. In this test, however, instead of scaling the number of simultaneous users, we instead held the test at 400 … Continue reading »
IE8, favicon.ico and silly server stunts
At first glance, load testing software seems like it should be pretty straightforward. And like most things, it turns out to be really complex — at least, if you want to do it well. Simulating a browser could be pretty easy – except for the need to do it very, very, very efficiently, so that the solution can scale to simulate hundreds or thousands of virtual users per computer.
What does this have to do with favicon.ico and IE8? Occasionally while helping a customer use Load Tester, we run into some behavior that is difficult to explain, and this was one … Continue reading »
AIX Monitoring Support on the Horizon
We’ve got a lot of new exciting progress making it’s way into Load Tester 4.2. Among these features, Load Tester 4.2 will be introducing an Advanced Server Analysis™ module designed for AIX servers. Like our other Advanced Server Analysis™ agents, the AIX module is capable of running offline, and will continue to collect data about your server even when normal connectivity to the server has been overloaded (unlike some of our competitors solutions). The monitoring agent can collect vital information from your server, including:
CPU
Memory
Disk activity (reads / writes / % utilization)
Network activity (bandwidth in & … Continue reading »
aiCache and Drupal: A Case Study
Note: This is Part 3 of an ongoing series on Drupal performance and load testing. If you haven’t already, read the introduction.
Load Testing Anti-Patterns: Building the Perfect Test
We run into a wide variety of customers who need load testing software and/or services. While many are working their way through the process on-the-fly, others have toiled long and hard to develop a thorough testing plan, complete with detailed descriptions of exactly how the load test should be performed. On occasion, this testing plan is incredibly specific – detailing exactly how many users should be doing this or doing that, exactly how many users should click a button at the same time, exactly which search result the user should follow, etc.
While I applaud the amount of effort put into … Continue reading »