Load Testing Blog
Showing posts tagged “Load Testing”
How To Manually Modify HTTP Requests in Load Tester 4.2
In older versions, Load Tester provided a simple interface for modifying the URI portion of an HTTP request. For example, you could add a query parameter or a path segment by adding it directly to the request line in the Edit HTTP Request-line/URL dialog.
In Load Tester 4.2, this process has been made slightly more complex but vastly more powerful. We’ll start by manipulating the URI field directly. To do so, select the specific transaction you wish to edit, then select the Fields View, then choose “Customize” from the “Choose customization” drop-down menu in the upper right … Continue reading »
Editing Datasets Made Easier in 4.2
In the upcoming release of Web Performance Load Tester 4.2 it is now easier to edit datasets. In previous releases of Load Tester, deleting rows of data required either selecting each row individually and manually deleting it or exporting the dataset to an excel spreadsheet, removing the data and importing the file back to Load Tester. With Web Performance Load Tester 4.2, you can now simply highlight all the rows you want to remove and click on the “remove dataset row” icon. Adding rows is just as easy, simply click on the “add dataset rows” icon.
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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 »
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 »
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 »
Knowing your Security with Stress Testing
In the past, we’ve had plenty of discussion on how performance effects user experience, and how that relates to conversions. But, can a server’s performance effect it’s security?
During a previous test, we had a customer whose site included a contact form. The user would complete the contact form in their browser, and the application server would convert this response into an e-mail and send it through a mail server. The contact form, coupled with the use of a CAPTCHA, helps to cut back on undesirable messages. During our testing, we discovered that the mail server was becoming overloaded (at only … Continue reading »
Choosing the scenarios for a load test
What to test?
Occasionally, we encounter customers who have only a single scenario to test. For example, one client developed an application in which the only scenario of interest involved a user registering him/herself with the system and scheduling an appointment. When this happens, the tester may devote their efforts to the accurate simulation, testing and analysis of this single scenario. You are unlikely to be so lucky.
In any moderately complex system, there are dozens or even hundreds of scenarios that are candidates for load testing. You are not likely to have the time or resources to test them all. As … Continue reading »
Testing tip: Make it Fail
We recently had a case of debugging a testcase where Load Tester reported an error with a page that looked and appeared just as it should, except it was missing a link the user needed to move forward. Debugging this case was easy: examine the replay two pages prior to the error, and the server had added a red error message to the page indicating the selected criteria was not valid.
So why didn’t Load Tester flag this error from the server? Beneath the error message, the page was exactly identical to the expect page: form fields were present and filled … Continue reading »
Tips for Successfully Testing from the Cloud
With Load Tester 4, we’ve made it easy to harness Amazon’s power for Load Engines quickly and inexpensively. Once you’ve familiarized yourself with the basics, here are a few rules of thumb:
1. Get to know the Amazon EC2 Console . The console will quickly tell you what instances you have running – and subsequently what you are getting billed for.
Note that the console shows you only data for a selected region, so you should check each region separately. Load Tester will automatically prompt you after a test and before shutting down Load Tester if you have running engines … Continue reading »