Dedup policy implement between grpc and proxy plugin (#3537)

Signed-off-by: zouyee <zounengren@cmss.chinamobile.com>

plugin/forward/policy.go

@@ -1,64 +0,0 @@
-package forward
-
-import (
-	"math/rand"
-	"sync/atomic"
-)
-
-// Policy defines a policy we use for selecting upstreams.
-type Policy interface {
-	List([]*Proxy) []*Proxy
-	String() string
-}
-
-// random is a policy that implements random upstream selection.
-type random struct{}
-
-func (r *random) String() string { return "random" }
-
-func (r *random) List(p []*Proxy) []*Proxy {
-	switch len(p) {
-	case 1:
-		return p
-	case 2:
-		if rand.Int()%2 == 0 {
-			return []*Proxy{p[1], p[0]} // swap
-		}
-		return p
-	}
-
-	perms := rand.Perm(len(p))
-	rnd := make([]*Proxy, len(p))
-
-	for i, p1 := range perms {
-		rnd[i] = p[p1]
-	}
-	return rnd
-}
-
-// roundRobin is a policy that selects hosts based on round robin ordering.
-type roundRobin struct {
-	robin uint32
-}
-
-func (r *roundRobin) String() string { return "round_robin" }
-
-func (r *roundRobin) List(p []*Proxy) []*Proxy {
-	poolLen := uint32(len(p))
-	i := atomic.AddUint32(&r.robin, 1) % poolLen
-
-	robin := []*Proxy{p[i]}
-	robin = append(robin, p[:i]...)
-	robin = append(robin, p[i+1:]...)
-
-	return robin
-}
-
-// sequential is a policy that selects hosts based on sequential ordering.
-type sequential struct{}
-
-func (r *sequential) String() string { return "sequential" }
-
-func (r *sequential) List(p []*Proxy) []*Proxy {
-	return p
-}