get route info in spring-cloud-gateway with opentelemetry-spring-boot-starter

[damianofontana-satispay]

Describe the bug

Metrics for dynamic routes exposed by Spring Cloud Gateway do not include the http.route attribute. The same issue was previously found in the Java agent and addressed here: #9597

Steps to reproduce

Create a spring cloud gateway application with 'io.opentelemetry.instrumentation:opentelemetry-spring-boot-starter'

Expected behavior

http.route attribute filled with the correct information

Actual behavior

While using spring-cloud-gateway, we always get null http.route because spring-cloud-gateway does not put the HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE in exchange object,

Javaagent or library instrumentation version

opentelemetry-spring-boot-starter 2.18.1

Environment

JDK: 21
OS: macOs 15:4
Spring Cloud Gateway: 2023.0.0
opentelemetry-spring-boot-starter: 2.18.1

Additional context

No response

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[jaydeluca]

The spring boot starter depends on library instrumentation, which is not currently available since there is only javaagent instrumentation at the moment. The first step would be to explore creating a library instrumentation for this functionality. Then we could include it in the starter.