To recapitulate from Chapter 8, Introduction to Spring Cloud, in reference to the Spring Cloud Sleuth and Zipkin for distributed tracing section, the tracing information from a complete workflow is called a trace or a trace tree, and sub-parts of the tree, for example, the basic units of work, are called a span. Spans can consist of sub spans forming the trace tree. The Zipkin UI can visualize a trace tree and its spans as follows:

Spring Cloud Sleuth can send trace information to Zipkin either synchronously over HTTP, or asynchronously using a message broker such as RabbitMQ or Kafka. To avoid creating runtime dependencies on the Zipkin server from the microservices, it is preferable to send trace information to Zipkin asynchronously using either RabbitMQ or Kafka. This...