TrueLog Impact on Scalability

TrueLog generation is only useful in as much as it is adaptable to your load-testing environment. Therefore, memory and performance requirements must be kept to a minimum.

The two major factors affecting TrueLog scalability are:
  • Performance downgrade
  • Memory usage

Performance Downgrade

Performance downgrades related to TrueLog generation can range from 0% - 10%. This is because runtime keeps all relevant data in memory and attempts to keep necessary memory allocations to a minimum. Note that the performance impact of TrueLog On Error is negligible.

Memory Usage

In terms of scalability, there is a tremendous difference between TrueLog and TrueLog On Error. The TrueLog feature immediately writes each request and response to a TrueLog file. The formatting of the TrueLog file produces high internal CPU usage and a large amount of IO for the writing of the TrueLog file.

As a result, TrueLog generation is often not suitable for load testing.

Since TrueLogs can become large in size, you can configure Silk Performer to generate TrueLogs only when errors are encountered during testing. While systems run accurately, nothing is recorded. Such targeted TrueLog generation is known as TrueLog On Error and results in smaller, focused TrueLog files.

Memory requirements for TrueLog On Error are largely dependant on the BDL scripts that are utilized. Therefore, generic percentages can not be given, especially in cases where TrueLog On Error is configured to log complete transactions. Note that this applies only to TrueLog On Error files for which the non-default Store TrueLog for one transaction setting has been selected. In such cases, memory usage correlates with the number and size of requested Web pages included in transactions. With the default Store TrueLog based on content history setting, the length of transactions has no impact. Content histories usually do not exceed five Web pages, and these are the only pages that must be stored.