Blocklist configuration for http client plugin does not work

[Quramy]

Expected behaviour

I read https://datadoghq.dev/dd-trace-js/interfaces/plugins.http.html#blocklist and it saids

List of URLs that should not be instrumented.

However, it seems that blocklist of http.client plugin implementation only effects whether to inject tracing headers or not. It seems that the plugin send span of an HTTP request matched in blocklist to agent.

dd-trace-js/packages/datadog-plugin-http/src/client.js

Lines 37 to 51 in 5326afb

	const span = this.tracer.startSpan('http.request', {
	childOf,
	tags: {
	'span.kind': 'client',
	'service.name': getServiceName(this.tracer, this.config, options),
	'resource.name': method,
	'span.type': 'http',
	'http.method': method,
	'http.url': uri
	}
	})
	if (!(hasAmazonSignature(options) || !this.config.propagationFilter(uri))) {
	this.tracer.inject(span, HTTP_HEADERS, options.headers)
	}

Is API document wrong ? 🤔

And I want to reject to instrument for some requests ( they can be detected via URL domain or path). Is there alternative way?

Actual behaviour

Steps to reproduce

Environment

• Operation system:: Docker (based from node:16.14.2-buster)
• Node.js version:: 16.14.2
• Tracer version: : 2.11.0
• Agent version:
• Relevant library versions:

[rochdev]

This was removed because of issues with the previous plugin system which has since been replaced. It should be possible to restore this feature at this point. I'll have to take a look at how to handle propagation of the sampling decision for these spans.

[clement-heliot]

This might be related: #2225

[rochdev]

@clement-heliot Thanks for the additional context in #2225. It wasn't clear to me what the use case was for this was, although it seems pretty clear now that it's basically the same reason that we drop our own requests to avoid seeing observability related requests. The main concern was wether we should just drop the span itself, or also any other spans following from that span, but for this use case it's definitely the latter. We should be able to add this back now.

[Quramy]

this use case it's definitely the latter.

👍

yes. I want to reject nested spans in an http-client span which matches the blocklist.

[dko-slapdash]

@rochdev Just spent 1h or so with an interactive debugger trying to figure out, why blocklist is ignored, finally figured out, and then found this thread. :-) What was another confusion is that the feature is mentioned as functioning in the official docs: https://docs.datadoghq.com/tracing/guide/ignoring_apm_resources/?tab=datadogyaml#tracer-configuration-options

Would be super-cool to have this feature back. Thanks!

[Quramy]

@rochdev Thanks!