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 »
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 »
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 »
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 »
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 »
In this example case, we ran into a situation where a load engine could not resolve the hostname of the server being tested, even though Load Tester was able to record & replay against the server without any difficulty. This problem appears immediately, but only when running a Load Test with the troubled load engine. By using the Engines View in Load Tester, we were able to select and use each Load Engine separately in a Load Test, until the faulty engine had been isolated (this sort of problem will show errors coming back from the engine within seconds, and … Continue reading »
Recently we have been getting a lot of questions regarding how to use Load Tester to record against local host. While it is possible to record a local server, and may be useful for testcase development, it is however not recommended to run a load test on the same machines as the local server. Running a load test on the server can produce confusing and misleading results as well as cause resource issues. In order to get useful results, Load Tester and the web server need to be on separate machines.
In order to record against the local host; use the … Continue reading »
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 »
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 »
Why am I doing this?
Even a well-executed Load Testing effort may fail if it does not answer the right questions…or answer them in the right way. The “right questions” might appear obvious, such as “How many hits/sec can the server handle?” Such questions, while well-intentioned, may not be the questions that really need to be answered. They may simply be the easiest questions to ask…and answer.
From a higher-level strategic level, the real questions sound something like:
1. Is this system ready to deploy?
2. Can we make this system available to another 350 users?
3. We deployed the system and the performance is … Continue reading »