A controller orchestrates a test concurrently running from multiple agents and consolidates performance metrics. An agent is an unattended computer with a StresStimulus instance which has agent mode turned on. The agent emulates virtual users in distributed tests, orchestrated by the controller.
A single StresStimulus software product performs three roles: Test Designer, Controller, and Load Agent. During the test design stage, the Designer is used for designing test scenarios (test script) and configuring test parameters. The Controller executes the test. It distributes the amount of load between Load Agents, coordinates their operation, collects and aggregates real-time performance metrics and generates final reports. The Load Agents operate concurrently under the orchestration of the Controller. Load Agent can be installed on a physical or virtual machine as well as on an AWS EC2 or Microsoft Azure instance. A diagram below shows an example of a distributed testing schema.