Apache http client 4.3 low level instrumentation

[laurit]

Not needing to keep track of redirects greatly simplifies the instrumentation.

[jeanbisutti]

Not needing to keep track of redirects greatly simplifies the instrumentation.

Coud you please explain why it's not needed? Perhaps add a comment in the Java code about this?

[laurit]

@jeanbisutti Have a look at https://github.com/open-telemetry/semantic-conventions/blob/main/docs/http/http-spans.md#http-client Spec says that Instrumentations SHOULD create an HTTP span for each attempt to send an HTTP request over the wire and If for some reason it is not possible to emit a span for each send attempt (because e.g. the instrumented library does not expose hooks that would allow this), instrumentations MAY create an HTTP span for the top-most operation of the HTTP client. We call the former a low level instrumentation and the latter high level instrumentation. Historically spec required high level instrumentation so that is what we usually implement. In this case besides being recommended by the spec low level instrumentation is also simpler.

Coud you please explain why it's not needed? Perhaps add a comment in the Java code about this?

With low level instrumentation we can start/end the span each time interceptor is called. With high level instrumentation we had to start the span when interceptor was first called and end it in the last call. Figuring out which of the interceptor calls was last required figuring out whether the client would be following the redirect or giving up.