How is the trace identifier transmitted for request tracking?

The trace ID for request tracking is usually transmitted in several ways:

• HTTP headers — the most common method. For example, in distributed systems, headers like X-Trace-Id or traceparent (in the W3C Trace Context standard) are often used. When a request is received, the service reads this header and passes it along the call chain.

• Execution context (ThreadLocal) — within an application, the trace ID can be stored in a ThreadLocal variable to ensure access from different parts of the code without explicit parameter passing.

• Logging and metadata — the trace ID is added to logs and request metadata for subsequent analysis.

Example of transmitting trace ID in an HTTP header:

GET /api/data HTTP/1.1
Host: example.com
X-Trace-Id: 123e4567-e89b-12d3-a456-426614174000

Thus, the trace ID passes through all services, allowing logs and traces to be linked in a single chain.