🐛 [Bug]: Adaptor + otelfiber issue

[kperreau]

Bug Description

If I combine the Adaptor + Otelfiber contrib Middleware, the method c.BaseURL() return the wrong value. (http:// instead of http://localhost:3000)

How to Reproduce

Steps to reproduce the behavior:
Use Adaptor + otelfiber middleware, then call the c.BaseURL() method from an handler.

Expected Behavior

Having the right base url http://localhost:3000 in my case.

Fiber Version

v2.49.2

Code Snippet (optional)

import (
	"github.com/gofiber/contrib/otelfiber"
	"github.com/gofiber/fiber/v2"
	"github.com/gofiber/fiber/v2/middleware/adaptor"
	"net/http"
)

func main() {
	app := fiber.New()

	app.Use(otelfiber.Middleware())

	app.Get("/test", func(c *fiber.Ctx) error {
		return c.SendString(c.BaseURL())
	})
	
	http.ListenAndServe(":3000", adaptor.FiberApp(app))
}

Checklist:

• I agree to follow Fiber's Code of Conduct.
• I have checked for existing issues that describe my problem prior to opening this one.
• I understand that improperly formatted bug reports may be closed without explanation.

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[kperreau]

I add some tests/context here.
Basically, call the endpoint http://localhost:3000/test should return the base url http://localhost:3000.

Fiber + Adaptator + Otelfiber

func main() {
	app := fiber.New()

	app.Use(otelfiber.Middleware())

	app.Get("/test", func(c *fiber.Ctx) error {
		return c.SendString(c.BaseURL())
	})
	
	http.ListenAndServe(":3000", adaptor.FiberApp(app))
}

Result: http://

Fiber

func main() {
	app := fiber.New()

	app.Get("/test", func(c *fiber.Ctx) error {
		return c.SendString(c.BaseURL())
	})
	
	app.Listen(":3000")
}

Result: http://localhost:3000

Fiber + Otelfiber

func main() {
	app := fiber.New()
	
	app.Use(otelfiber.Middleware())

	app.Get("/test", func(c *fiber.Ctx) error {
		return c.SendString(c.BaseURL())
	})
	
	app.Listen(":3000")
}

Result: http://localhost:3000

Fiber + Adaptator

func main() {
	app := fiber.New()

	app.Get("/test", func(c *fiber.Ctx) error {
		return c.SendString(c.BaseURL())
	})
	
	http.ListenAndServe(":3000", adaptor.FiberApp(app))
}

Result: http://localhost:3000

[praem90]

The Hostname method on the ctx.go getting called for 3 times for the above example.

The c.fasthttp.Request.URI().Host() returns the correct hostname for the first time but for the further calls returns empty.

Anyone can help me to debug this?

[VikasManohar]

This is my first time trying to contribute, so I may be wrong😃

• From what I could find, adaptor fills Host in only fasthttp.Request.uri but not in fasthttp.Header.
• otelfiber resets fasthttp.Request.uri and tries to add the host from fasthttp.Header, but since host field in fasthttp.Header is nil, fasthttp.Request.uri.host is also set to nil.
• Hence c.Hostname() returns empty when using Fiber + Adaptator + Otelfiber

---

Using the code snippet given in description for Fiber + Adaptator + Otelfiber, this is the trace:

Following line in adaptor.go sets these values among other things:

fiber/middleware/adaptor/adaptor.go

Line 69 in fa88733

func HTTPMiddleware(mw func(http.Handler) http.Handler) fiber.Handler {

c.fasthttp.Request.Header.host -> nil
c.fasthttp.Request.uri.host -> 127.0.0.1:3000
c.fasthttp.Request.parsedURI - > true

Following function in fiber.go is called by otelfiber middleware: https://github.com/gofiber/contrib/blob/27b59cf2d203608e9e22a367d275822d3456ae26/otelfiber/fiber.go#L35

func Middleware(opts ...Option) fiber.Handler 

Then the function in this file is called semconv.go : https://github.com/gofiber/contrib/blob/27b59cf2d203608e9e22a367d275822d3456ae26/otelfiber/semconv.go#L32

	- func httpServerTraceAttributesFromRequest(c *fiber.Ctx, cfg config) []attribute.KeyValue
	         ...
		semconv.NetHostNameKey.String(utils.CopyString(c.Hostname()))
		semconv.HTTPTargetKey.String(string(utils.CopyBytes(c.Request().RequestURI()))),
			c.fasthttp.Request.parsedURI - > false <--
		semconv.NetHostNameKey.String(utils.CopyString(c.Hostname())),
		    - return c.app.getString(c.fasthttp.Request.URI().Host())
			func (req *Request) URI() *URI
				func (req *Request) parseURI() error
					return req.uri.parse(req.Header.Host(), req.Header.RequestURI(), req.isTLS) <-- this line executes as `c.fasthttp.Request.parsedURI` is set to "false" in the earlier line.

req.uri.parse function resets uri and repopulates uri.host from header.host, but req.Header.Host() is not set when adaptor is used

---

• The fix would be for adaptor to set the host in fasthttp.Header field after this line : https://github.com/gofiber/fiber/blob/fa887332189ea9dc0bec8c33be5cefe9e7c817ae/middleware/adaptor/adaptor.go#L77C2-L77C2

req.Header.SetHostBytes([]byte(r.Host))

• I tested with this locally, if the fix looks ok, I will be happy to raise a PR 😃

[efectn]

@VikasManohar you can create a PR. We can use r.URL.Host for the cases that have empty r.Host. However it doesn't seem good idea for non-proxy servers. It's better to check Host header

[kperreau]

Any update on this one?

[rharshit82]

Hi, I can raise PR for the same. @efectn Can you please assign me this issue?

[efectn]

Hi, I can raise PR for the same. @efectn Can you please assign me this issue?

Done