http: superfluous response.WriteHeader

[cachalots]

There are many error logs in the IPFS gateway.

http: superfluous response.WriteHeader call from github.com/ipfs/boxo/gateway.webError (errors.go:175)

http: superfluous response.WriteHeader call from github.com/ipfs/boxo/gateway.webError (errors.go:165)

Calling writeError after writeHeader will trigger this error. I'm not sure if this part of the code is causing it, but this code will trigger this issue.

boxo/gateway/handler.go

Lines 921 to 928 in 6602207

	w.WriteHeader(http.StatusBadRequest)
	if err := redirectTemplate.Execute(w, redirectTemplateData{
	RedirectURL: intendedURL,
	SuggestedPath: intendedPath.String(),
	ErrorMsg: fmt.Sprintf("invalid path: %q should be %q", r.URL.Path, intendedPath.String()),
	}); err != nil {
	i.webError(w, r, fmt.Errorf("failed to redirect when fixing superfluous namespace: %w", err), http.StatusBadRequest)
	}

[lidel]

@cachalots

• how are you using boxo/gateway? as a library in you app?
• do you have more than a single mux / listener / instance of gateway?

Mind providing the smallest demo.go that reproduces the issue?

[cachalots]

@lidel https://github.com/4everland/ipfs-servers/blob/dev/app/gateway/internal/server/http.go
Same usage as in example, only replacing the implementation of blockstore.
In theory, if there are enough requests, the gateway example should also reproduce this error. This error was reported by net/http, so it's not easy to assert which location triggered this error.