Web Load Test Ramping Best Practices: PART 2
By: Stefan Karytko
In part one, I discussed the importance of understanding the benefits ramping load can have on web load test results. In this post, I’ll discuss best practices for determining how long to ramp at the beginning of a web load test.
The general the rule of thumb for load test ramping is the slower the ramp the better. Of course, given time and cost restraints, the goal of most testers is to run the most effective test possible in the least amount of time. With this in mind, here are some best practices for determining how long to ramp at the beginning of a load test:
Determine the goal of the test – If the purpose of the test is to determine at what point the application’s performance bottleneck is, then the ramp should be slower and more gradual. If the purpose is to measure performance at a specific pre-defined load level, then a shorter ramp and a longer hold period will suffice.
All tests should have a minimum 20 minute ramp period – To ensure that load is consistently and evenly applied during the test, a minimum of 20 minutes of ramping is recommended for each test.
The longer it takes to complete a transaction, the longer the ramp period – Determine the total time it takes to complete a transaction (make sure to include any think time). If the average transaction takes over 2 minutes to complete, add an additional 5 minutes to the ramp for each additional minute. For example, if the average transaction takes 4 minutes to complete, add 10 minutes to your ramp.
When Ramping Is Not Necessary
An example of a test where a slow gradual ramp of load is not necessarily useful or desired is in a flash test. The purpose of a flash test is to mimic scenarios where a high number of visitors visit a website in a very short period of time.
This is common in situations that involve sales promotions or coupons or special events that are time sensitive. In this scenario it’s required to apply as much traffic and load to the application as quickly as possible. The quickest way to accomplish this is to have a very short ramp or to remove the ramp all together.
A common practice used during many load tests is to ramp down at the end of the test. The purpose of this is to slowly lower load and traffic levels on a system to allow the system to gracefully recover from higher load levels.
When using web load, the benefits of ramping down are minimal and the tests themselves will naturally ramp down as virtual users complete their last transaction at different times before shutting down. Removing the ramp down phase reduces the amount of time and cost of each test.
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