Distributed Tracing (Sleuth and Zipkin).

Why needed?

In Microservices, a single request might traverse 10+ services. Without tracing, it's impossible to know where a delay or error occurred.

Key Concepts:

• Trace ID: A unique ID for the entire request journey.
• Span ID: A unique ID for a specific segment/hop (service call) within that journey.

Implementation:

• Spring Cloud Sleuth / Micrometer: Automatically adds Trace IDs and Span IDs to logs and headers.
• Zipkin: A visual UI to see the timing and flow of these traces across services.