Allow ability to add attributes to span with otelhttp span

[rbkumar88]

Problem Statement

Add ability to add custom span attributes to the span with instrumentationScopeName go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp and kind client

Proposed Solution

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Alternatives

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Prior Art

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Additional Context

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[dmathieu]

Your request is rather unclear.
You can retrieve the current span and add attributes to it at any moment.

span := trace.SpanFromContext(req.Context())
span.SetAttributes(attribute.Bool("isTrue", true), attribute.String("stringAttr", "hi!"))

So all you need to add custom attributes to the current span in HTTP, is a custom handler/middleware that retrieves the span and does what you wish to do.

[rbkumar88]

@dmathieu i could customize the span name of the span created by otelhttp (instrumentationScopeName: go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp) and (kind: client), the one like below

cloud#region	dev
error	true
http#method	POST
http#request_content_length	109
http#status_code	404
http#url	http://localhost:8080/
instrumentationScopeName	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp
instrumentationScopeVersion	0.59.0
kind	client
net#peer#name	localhost
net#peer#port	8080
os#type	darwin
status_code	ERROR`

When I try to add like below
span := trace.SpanFromContext(req.Context()) span.SetAttributes(attribute.Bool("isTrue", true), attribute.String("stringAttr", "hi!"))

it is adding the attributes to the parent span, but not to the one above.

[dmathieu]

If you're talking about the span for an outgoing HTTP call, it's even easier.
You can use the WithSpanOptions option to do just that.

client := http.Client{
  Transport: otelhttp.NewTransport(
    http.DefaultTransport,
    otelhttp.WithSpanOptions(
      trace.WithAttributes(
        attribute.Bool("isTrue", true),
        attribute.String("stringAttr", "hi!"),
      ),
    ),
  ),
}

[rbkumar88]

Is there a way to add per request span attributes. for example. i want to extract some fields from request body and set them as span attributes. the above is while initializing the http.Client

[dmathieu]

A custom HTTP transport would allow you to hook into the middle of the request, and modify the span.