No eventing-level spans in tracing visualization

[ashrafguitoni]

Describe the bug

We're using the tracing setup described in the knative docs where we can see the request progressing across knative components in Jaeger UI. After having to reinstall the tracing setup (for infrastructure-related reasons), the eventing components don't show up in the traces anymore.

Expected behavior

Request traces include eventing-level traces, for example like this (an old screenshot):

Actual behavior

The trace only includes serving-level traces:

To Reproduce

• Setup tracing as described in the docs
• Deploy a knative service and a knative kafka source that simply redirects requests to the service
• Send a request and search for the trace in Jaeger UI

Knative release version

• Knative serving: v1.12.0
• Knative eventing core: v1.12.6
• Knative kafka source: v1.12.9