Added LBEndpoint field in routing.LBContext struct

[RomanZavodskikh]

The routing.Route field of routing.LBContext struct will be eventually removed because loadbalancer in general does not require the full information about route, only about endpoints to balance load between.

You can think about this PR as preliminary one for the #2634

[AlexanderYastrebov]

Lets do this either at the place where context is created or maybe better move context creation here.

[RomanZavodskikh]

Lets do this either at the place where context is

I like this idea, I've done that.

or maybe better move context creation here.

I like this way less, because I need to redeclare a lot variables from func mapRequest(... in func setRequestURLForLoadBalancedBackend(...

diff --git a/proxy/proxy.go b/proxy/proxy.go
index 80b41df3..dddf641f 100644
--- a/proxy/proxy.go
+++ b/proxy/proxy.go
@@ -468,7 +468,13 @@ func setRequestURLForDynamicBackend(u *url.URL, stateBag map[string]interface{})
        }
 }
 
-func setRequestURLForLoadBalancedBackend(u *url.URL, rt *routing.Route, lbctx *routing.LBContext) *routing.LBEndpoint {
+func setRequestURLForLoadBalancedBackend(ctx *context, registry *routing.EndpointRegistry) *routing.LBEndpoint {
+       r := ctx.request
+       rt := ctx.route
+       stateBag := ctx.StateBag()
+       u := r.URL
+       lbctx := &routing.LBContext{Request: r, Route: rt, LBEndpoints: rt.LBEndpoints, Params: stateBag, Registry: registry}
+
        e := rt.LBAlgorithm.Apply(lbctx)
        u.Scheme = e.Scheme
        u.Host = e.Host
@@ -490,7 +496,7 @@ func mapRequest(ctx *context, requestContext stdlibcontext.Context, removeHopHea
                setRequestURLFromRequest(u, r)
                setRequestURLForDynamicBackend(u, stateBag)
        case eskip.LBBackend:
-               endpoint = setRequestURLForLoadBalancedBackend(u, rt, &routing.LBContext{Request: r, Route: rt, LBEndpoints: rt.LBEndpoints, Params: stateBag, Registry: registry})
+               endpoint = setRequestURLForLoadBalancedBackend(ctx, registry)
        default:
                u.Scheme = rt.Scheme
                u.Host = rt.Host

[AlexanderYastrebov]

This is actually better because it nicely contains all endpoint selection logic and creates a place to extend in the future.
Also

	u.Scheme = e.Scheme
	u.Host = e.Host

can be moved out of setRequestURLForLoadBalancedBackend as its not related to endpoint selection,
setRequestURLForLoadBalancedBackend could be renamed to selectLoadBalancedEndpoint (or something alike)

[AlexanderYastrebov]

#2652

[AlexanderYastrebov]

👍

[RomanZavodskikh]

👍