Proxy middleware: add ModifyRequest function to modify http.Request before proxy

[binhnguyenduc]

The proxy middleware currently does not allow any modification to the request, only ModifyResponse. This PR adds that option so caller can pass a custom function to be applied to requests before it hits reverse proxy.

I have also added passing test.

Please consider merging this as it would allow for more flexibility when proxy with Echo.

Thanks!

[aldas]

this has to be removed

[aldas]

I think Transport field provides similar functionality as you can create your own http.RoundTripper which modifies request:

type MyRoundTripper struct {
	accessToken string
	r           http.RoundTripper
}

func (mrt MyRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
	r.Header.Add("Authorization", "Bearer: "+mrt.accessToken)
	return mrt.r.RoundTrip(r)
}

func main() {
	e := echo.New()

	e.Use(middleware.ProxyWithConfig(middleware.ProxyConfig{
		Transport: MyRoundTripper{},
	}))

	log.Fatal(e.Start(":8080"))
}

https://stackoverflow.com/questions/51325704/adding-a-default-http-header-in-go

[asad-awadia]

@aldas is it possible to modify the proxy target urls at runtime?

[aldas]

I think you are looking for:

echo/middleware/proxy.go

Line 69 in 4a1ccdf

ProxyBalancer interface {

and look how commonBalancer works

[asad-awadia]

@aldas oh so I can use the returned object from NewRoundRobinBalancer to change the proxy targets by calling the appropriate methods?

The interface is already implemented internally? I just have to call addTarget with the right parameter ?