Running Multiple Virtual Users

When running multiple browser sessions in parallel, Silk Performer must make sure that these sessions operate independently from each other. Cache, cookie data base, and history in particular must not be shared across virtual users to simulate real user load. The separation of virtual users with regards to browsers is called browser sandboxing, meaning each virtual user runs its browser in its own environment.

To run browsers in sandboxed mode, Silk Performer uses different browser-dependent techniques.

Internet Explorer

For performance and resource reasons, Silk Performer does not use a full Internet Explorer browser instance to simulate a virtual user, but an Internet Explorer ActiveX control. The default behavior of the Internet Explorer control is to maintain a single cookie database, cache, and history across browser instances started by a particular Windows user. For load tests, Silk Performer reconfigures an Internet Explorer control to maintain one cookie database, cache, and history for each virtual user.

As each virtual user has its own independent Internet Explorer sandbox, it is possible to accurately simulate first-time and revisiting user behavior, as is used in the protocol-based approach to Web simulation.

Chrome and Firefox

These browsers provide their own mechanism to create independent browser sessions. As a driver engin, Silk Performer uses the corresponding WebDriver interface and some custom enhancements to enable them to run in a load testing environment.