http.route set to {{contextPath}}/* for all request not mapped in servletMapping

[aditya-32]

In Otel for all requests hit to a path that is not exposed or mapped in servletMapping (servletRegistration.getMappings()), http.route is set to {servletContextPath}/*
for example
i'm running a java application using tomcat 10 with jakarta servlets and i have mapped /rtb/internal/openx in servletMappings and if i make request at /rtb/internal/openx then the http.route is correct and set to value /rtb/internal/openx but if i make request to /rtb/internal/openx/ then since it was not exposed not added to servletMappings, hence it's http.route is set to /rtb/*.

Can someone please help me in understanding the use case as well as where can i find the code in repo , i tried checking for it in tomcat as well as servlet instrumentation but could not find exact code which is responsible for this transformation/updation for http.route

[laurit]

See

opentelemetry-java-instrumentation/instrumentation/servlet/servlet-common/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/servlet/ServletSpanNameProvider.java

Line 25 in 1c07aa5

public String get(Context context, MappingResolver mappingResolver, REQUEST request) {

[aditya-32]

is there a way to het the actual path for those 404 cases as well?

[laurit]

https://opentelemetry.io/docs/specs/semconv/http/http-spans/#name states that the span name must have a low cardinality. Paths that return 404 can potentially have a high cardinality. Spec says

Instrumentation MUST NOT default to using URI path as span name, but MAY provide hooks to allow custom logic to override the default span name.

It is possible to use manual instrumentation to overwrite the span name set by the agent.