The X-Instana-Service is a specific HTTP header that Instana sensors are pre-configured to automatically recognize and process. If this header is present in an incoming request, its value is used to name the service for that particular transaction, overriding any other service naming configurations. This mechanism allows for dynamic service naming on a per-request basis. The collection and use of this header are a built-in, automatic feature of the Instana instrumentation and do not require additional custom configuration in the agent.

A. x-client-id: This is an example of a generic custom header. Instana does not collect arbitrary HTTP headers by default and requires explicit configuration to capture them.

B. Instana-probe: This is not a standard, documented Instana header that is automatically collected for general tracing or service monitoring purposes.

C. Instana-id: This is not a standard Instana header. Trace context, including trace and span IDs, is propagated via the X-INSTANA-T and X-INSTANA-S headers.

1. IBM Documentation, Instana Observability on SaaS, "Naming services": This document explicitly states, "You can set a service name for a specific request by using the X-Instana-Service HTTP header. When you set the header on a request, it will take precedence over all other service naming configurations." This confirms the header is automatically processed for service naming.

2. IBM Documentation, Instana Observability on SaaS, "Monitoring custom HTTP headers": This source clarifies the default behavior for other headers: "By default, Instana does not collect HTTP headers as it can contain sensitive data. However, the feature can be enabled on-demand..." This directly contrasts with the automatic handling of X-Instana-Service and shows why option A is incorrect.