HTTP headers for distributed trace (observability) - Part 1: Spring Cloud Sleuth

This series of posts investigates the HTTP headers used to support tracing, which is one of the pillars of observability (also composed of logs and metrics). Although we focus on investigating these headers, these posts also serve as an introduction to distributed tracing and as a presentation of some technological alternatives for its implementation.

In particular, the question is: could we produce an in-house solution for distributed tracing with HTTP headers compatible with market solutions? Such an approach could bring portability and interoperability gains.

For this quest, I started investigating Sleuth (Spring Boot’s distributed tracing subsystem) and OpenTracing. In this first post, we will focus on Sleuth.

The complete post is available only in Portuguese.

Post digest

Sleuth is part of Spring Boot, a very popular framework for developing web applications in Java. A service using Sleuth will have each entry in its log associated with a span ID and a trace ID, with the span ID identifying the processing that occurred in the service, while the trace ID represents the distributed transaction.

The span ID is typically transferred from one service to another via the X-B3-SpanId header, while the trace ID is transferred via the X-B3-TraceId header. Other data linked to the distributed transaction can be transferred between services via “baggage”, which are extra headers with names starting with baggage-.

Sleuth can also expose all of these aforementioned values to OpenZipkin, which is a visual interface that allows humans to analyze the details of distributed transactions, especially the processing time spent on each service.

In the next post in the series we will analyze OpenTracing.