Much of the power of a telemetry pipeline derives from the transformation of telemetry between when the Emitting stage receives it from the production systems and when telemetry is displayed to a human by the Presentation stage. Each of the three stages of the telemetry pipeline—Emitting (chapter 2), Shipping (chapters 3 and 4), and Presentation (chapter 5)—has the opportunity to enhance telemetry. The two biggest forms of added value are the right side of figure 6.1:
- Marking up telemetry by adding context regarding where it originated, providing clues to people asking questions about where and when certain events happened. This context can include execution details such as the browser session, server identifier, and software version that produced a piece of telemetry, as well as business details such as payment level, user type, and team identifier.
- Enriching telemetry by transforming the format to improve the ability of the Presentation stage to answer questions and providing correlations between events, such as taking a phrase like processed 2 pages and parsing it to produce a database field named pages with a value of 2.