Why Handler registered by http.HandleFunc is called twice?

[kawamoto]

In the below code, "hello" is called twice when I accessed to
http://localhost:8080. why?

package main

import (
"fmt"
"net/http"
)

func main() {
http.HandleFunc("/", handler)
http.ListenAndServe(":8080", nil)
}

func handler(w http.ResponseWriter, r *http.Request) {
fmt.Println("hello")
}

[Dave Cheney]

Your browser is requesting /favicon.ico, this matches the catchall
handler, "/" so you get called twice.

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[Scott Lawrence]

If you log the request, you'll see your browser is probably also requesting
/favicon.ico, which is being passed to that same handler.

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--
Scott Lawrence

go version go1.0.3
Linux baidar 3.8.3-2-ARCH #1 SMP PREEMPT Sun Mar 17 13:04:22 CET 2013 x86_64 GNU/Linux

[Jan Mercl]

On Fri, Mar 22, 2013 at 12:17 PM, Dave Cheney <da...@cheney.net> wrote:
> Your browser is requesting /favicon.ico, this matches the catchall
> handler, "/" so you get called twice.

I think this is a FAQ candidate.

-j

[Yasutaka Kawamoto]

Thanks All

I got.

I use Google Chrome.
How do you avoid it?


2013/3/22 Scott Lawrence <byt...@gmail.com>:

[nvcnvn]

func main() { 

        http.HandleFunc("/favicon.ico", handlerICon) 

        http.HandleFunc("/", handler) 
        http.ListenAndServe(":8080", nil) 
} 

Vào 18:57:21 UTC+7 Thứ sáu, ngày 22 tháng ba năm 2013, kawamoto đã viết:

[Yasutaka Kawamoto]

Oh... I see.
I could run in below code.

package main

import (
"fmt"
"net/http"
)

func main() {

http.HandleFunc("/favicon.ico", handlerICon)
http.HandleFunc("/", handler)
http.ListenAndServe(":8080", nil)

}

func handler(w http.ResponseWriter, r *http.Request) {
fmt.Println("hello")
}

func handlerICon(w http.ResponseWriter, r *http.Request) {}


Thanks!


2013/3/22 nvcnvn <nvc...@gmail.com>:

[Jeremy Wall]

if you just want to verify it only gets called once you can always hit the url with curl which won't generate extra http requrests for you.

[Yasutaka Kawamoto]

I got it.

When I don't write "http.HandleFunc("/favicon.ico", handlerICon)" and
I hit the url with curl,
I checked it only gets once.

Thank you for the information.

2013/3/23 Jeremy Wall <jw...@google.com>:

[Jason]

I have a meta-question: Why is "/" a catch-all URL instead of "" (or almost anything else)? This also bit me when I wrote a "/" handler, and I expect it's common for someone to write a specific handler for their HTTP server home page. There doesn't seem to be a way to specify that special handler, though.

[atomly]

On Mon, Mar 25, 2013 at 2:54 PM, Jason <jki...@gmail.com> wrote:

I have a meta-question: Why is "/" a catch-all URL instead of "" (or almost anything else)? This also bit me when I wrote a "/" handler, and I expect it's common for someone to write a specific handler for their HTTP server home page. There doesn't seem to be a way to specify that special handler, though.

Yeah, it feels like it should be "/*" or "*" or something, with "/" specifically referring to "/" and only "/"... 

:: atomly ::

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[Jason]

Well, sure, but that specifies a resource (the root resource). Why should it stand in for:

/

/favicon.ico

/foo/bar

etc.?

On Monday, March 25, 2013 3:00:37 PM UTC-4, kara...@gmail.com wrote:

Because when you request a page in http the minimum request is : GET / HTTP/1.1

IMHO, since / is the root of your server in http, they used that naming for the handler too.

[Liigo Zhuang]

+1

[Brad Fitzpatrick]

This is https://code.google.com/p/go/issues/detail?id=4799