Customizing span kind in Netty server with auto-instrumentation

[orangain]

I have built a web application using Netty server (and Ktor) and set up Open Telemetry's auto-instrumentation using javaagent. In this case, Netty server instrumentation automatically creates spans with the SERVER Kind, but I want to configure it as follows:

• If the request path starts with /from-pubsub/: Kind should be CONSUMER
• Otherwise: Kind should be SERVER

How can I configure this?

Alternatively, if it is possible to change the Kind of an automatically created span midway, that would also be fine, but I think it might be difficult based on the following issue:

open-telemetry/opentelemetry-java#1793

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Versions:

• Ktor Server 2.2.4
• Netty: 4.1.86
• Open Telemetry: 1.24.0

[mateuszrzeszutek]

Hey @orangain ,

I can think of 2 ways to achieve that:

1. You could probably use the collector's transform processor to change the span kind for the given route
2. Or, you'd have to manually instrument your server code, and turn off the ktor javaagent instrumentation. This'd also require making some changes in the ktor library instrumentation to allow modifying the SpanKindExtractor

[trask]

this kind of change would be a good addition to this project

I'm not sure I understand the proposal here, can you outline (very) briefly?

[mateuszrzeszutek]

Having an option to pass a Function<SpanKindExtractor, SpanKindExtractor> to the Ktor library instrumentation. There are some library instrumentations that allow customizing the span name or status in a similar way; I think we could do the same for the span kind.

[orangain]

@mateuszrzeszutek Thank you for the clarification! I will send a pull request for that change.

[mateuszrzeszutek]

Thanks!

[orangain]

I've created #8255.