High Performance Responsive Design

Chapter 6. Continuous Web Performance Testing

Maintaining a Steady Course

As any student of systems theory knows, when you’ve made a positive change to a system, you can maintain that change via feedback loops to check state and course correct as necessary. This is as true for a thermostat regulating the temperature of an area as it is to keep the web performance metrics of a website within range of an SLA during new feature development.

Essentially, feedback loops are tools used in control systems to assess the output of the system and thus correct the system’s course if needed. At a very high level, they work like the flow shown in Figure 6-1, in which the output of a process is evaluated, giving feedback which becomes input that then feeds the process again.

Figure 6-1. Basic feedback loop diagram

For software engineering, one of the most effective procedural feedback loops is the practice of continuous integration. Continuous integration (CI) is essentially having mechanisms in place that build your code as new code is committed, check for different success criteria, and break the build—effectively putting a stop to check-ins and deployments—until the success criteria is again satisfied. Figure 6-2 depicts the feedback look diagram updated to represent a continuous integration workflow.

Figure 6-2. A CI feedback loop

At this point, you most likely have a CI environment set up in your ...