Host based routing

[mertenvg]

I use host based routing / grouping in quite a few of the projects I work on. Have you had any thoughts about routing based on Host (or possibly even other headers)? I've set up a rudimentary alternative using middleware but might be better in the router itself.

[vishr]

@mertenvg I have limited knowledge here, can you provide some examples or how is it done in other libraries or servers?

[axdg]

From what I can see most other libraries aren't implementing this functionality themselves. The same issue has been brought up for both Goji (here) and httprouter (here) - the solution seems to be to put some sort of hosts handler in front of the router. In Echo, this would be something like:

package main

import (
    "net/http"

    "github.com/labstack/echo"
)

type Hosts map[string]http.Handler

// Implement a ServeHTTP method for Hosts type.
func (h Hosts) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    // Check for host x in the Hosts map.
    if handler := h[r.Host]; handler != nil {
        handler.ServeHTTP(w, r)
    } else {
        // No handler is registered so redirect.
        // Not sure redirect is appropriate here?
        // This is just for illustration, else branch could just as easily return
        // an error for bad port, notFound for bad subdomain etc.
        http.Redirect(w, r, "http://a.localhost:8080", http.StatusTemporaryRedirect)
    }
}

func main() {

    // Some subdomains
    a := echo.New()
    b := echo.New()

    // Host maps.
    hosts := make(Hosts)
    hosts["a.localhost:8080"] = a
    hosts["b.localhost:8080"] = b

    // Handler for subdomain a.
    a.Get("/", func(c *echo.Context) error {
        c.String(http.StatusOK, "Welcome to host a...")
        return nil
    })

    // Handler for subdomain b.
    b.Get("/", func(c *echo.Context) error {
        c.String(http.StatusOK, "Welcome to host b...")
        return nil
    })

    http.ListenAndServe(":8080", hosts)
}

[vishr]

@axdg Thank you! It's probably better to keep it outside the router.

[mertenvg]

Thanks @axdg. I'm happy with that solution also