Load Testing Blog
Baseline the Performance of the Old System
If your project is replacing an existing system, it is immensely valuable to establish a baseline for the new system based on the existing system. Start by analyzing the usage patterns of the existing site. What operations are most common? What paths are users following through the site? How many users are accessing the system at various times throughout the day? Wherever possible, this data should come from system logs rather than assumptions and guesswork. Then start designing your test:
Create a mix of scenarios that account for 70-80% of the site usage
Add any other scenarios that are known, or suspected, … Continue reading »
Systems never pass the first test
Out of our entire list of services customers, only a handful have satisfied their performance goals on the first test. Of those, all but one had been through a performance testing campaign with us in the previous year. If this is the first time for your project or your organization to undertake performance testing, you are virtually guaranteed to fail the first test.
There is a large list of things that can go wrong with modern web systems – firewalls, load balancers, databases, web servers and, of course, the code. One setting buried deep in an … Continue reading »
Tips for Implementing a Content Delivery Network
This post will focus on providing tips for implementing a CDN. Since there are multiple CDN providers, each with their own setup procedures, configuration of a CDN will be contingent on the provider and the service rendered. However, whether it be a CDN for a blog or website, the following pointers will be useful while implementing a CDN.
Ensure that YSlow recognizes the CDN. YSlow is pre-loaded with a list of popular Content Delivery Networks, however all CDNs are not included in the list. If a CDN is not included in the list, a site will most likely get an F … Continue reading »
Load Test preparation will take longer than you think
Our first-time services customers greatly under-estimate the time required to get the first test configured and ready to run. In these cases, they have employed us to design the tests and develop the testcases – so that part goes pretty quick. What they, and other first-time load testers, don’t account for is the amount of time required for their people to:
Decide what to test
Create a set of test data in the system (e.g. test accounts with usernames and passwords)
Install monitoring tools on servers
Implement/execute backup and restore procedures
Deciding what to test may require interviews with end-users, … Continue reading »
Load Test Often!
Having performance testing results from frequent points in the development timeline can help developers understand the performance impact of various code and system changes. When testing early in the development process on a test rig that is not equivalent to production, the performance numbers are not valuable in their own right, but _changes_ in the performance numbers can extremely valuable. These changes can reveal newly-introduced performance bottlenecks that should be investigated.
For each new development iteration, the previous test (which does not exercise the new functions) should be repeated to determine if the changes had an effect on the performance of … Continue reading »
Identify Performance Goals Early…and Measure Them!
When a load test is complete, you will be asked “How did we do?” Do you know how will you answer that question? Our customers come to us and know, for example, that they need their site to handle 1000 users, but they frequently cannot tell us what “handle 1000 users” means to them. You will need to know which metrics are important and what the goals for those metrics are – preferably long before you start testing.
The first step is to determine what you should be measuring. For websites, you will typically be interested in page duration – how long it … Continue reading »
Content Delivery Networks
When our customers have bandwidth limitations or latency issues, we often encourage them to use a Content Delivery Network. A Content Delivery Network can offer a variety of benefits. What is a Content Delivery Network and what are the pros and cons of using one?
A Content Delivery Network is a cluster of web servers located in different parts … Continue reading »
Load Test Early!
Customers occasionally ask us “How early should we begin load testing?”
The answer is to test something, anything, as soon as the architecture is available. Performance problems have a wide variety of causes – from a single line of code to a load balancer setup; from a database schema to a server config file. Early in the development of the software you can catch simple coding problems and fundamental architectural limitations that are much easier to fix before a lot of code has been written.
Now, a word of caution: Testing against a scaled-down development or … Continue reading »
Performance Starts with the Developers
Performance starts with the developers as well as the server and network administrators. High-capacity websites do not happen by accident. To perform well and scale big, the system must be designed, built and configured for performance. That means it must be coded and configured with performance in mind, right from the start. Make sure the developer and admins all understand the levels to which the system must perform. Don’t make them guess what “it has to be fast” means.
Two of the most important tasks the test and project management teams to can do to help:
Identify the performance goals for the … Continue reading »
Load Tester 4.3 Improvements: Speculative Authentication for IE8 and IE9
Load Tester 4.3 carries a number of improvements for both ease of configuration, and accuracy of test simulation. Among these improvements comes support for speculative authentication, allowing Load Tester to simulate behavior from IE 9. The speculative authentication is only used for HTTP authentication schemes used by Load Tester’s Connection Negotiation Authentication feature. More information about HTTP authentication is available under How HTTP Authentication works and why load testers should care.
To describe the speculative authentication feature, it is easiest to simply look at a testcase using Basic Authentication.
Continue reading »