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

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

plugin/forward/forward.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/plugin/debug"
+	"github.com/coredns/coredns/plugin/pkg/policy"
 	clog "github.com/coredns/coredns/plugin/pkg/log"
 	"github.com/coredns/coredns/request"
 
@@ -25,7 +26,7 @@ var log = clog.NewWithPlugin("forward")
 // of proxies each representing one upstream proxy.
 type Forward struct {
 	proxies    []*Proxy
-	p          Policy
+	p          policy.Policy
 	hcInterval time.Duration
 
 	from    string
@@ -43,7 +44,7 @@ type Forward struct {
 
 // New returns a new Forward.
 func New() *Forward {
-	f := &Forward{maxfails: 2, tlsConfig: new(tls.Config), expire: defaultExpire, p: new(random), from: ".", hcInterval: hcInterval}
+	f := &Forward{maxfails: 2, tlsConfig: new(tls.Config), expire: defaultExpire, p: new(policy.Random), from: ".", hcInterval: hcInterval}
 	return f
 }
 
@@ -91,8 +92,8 @@ func (f *Forward) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
 			}
 			// All upstream proxies are dead, assume healthcheck is completely broken and randomly
 			// select an upstream to connect to.
-			r := new(random)
-			proxy = r.List(f.proxies)[0]
+			r := new(policy.Random)
+			proxy = r.List(f.proxies)[0].([]*Proxy)[0]
 
 			HealthcheckBrokenCount.Add(1)
 		}
@@ -188,7 +189,12 @@ func (f *Forward) ForceTCP() bool { return f.opts.forceTCP }
 func (f *Forward) PreferUDP() bool { return f.opts.preferUDP }
 
 // List returns a set of proxies to be used for this client depending on the policy in f.
-func (f *Forward) List() []*Proxy { return f.p.List(f.proxies) }
+func (f *Forward) List() []*Proxy {
+	if len(f.p.List(f.proxies)) == 1 {
+		return f.p.List(f.proxies)[0].([]*Proxy)
+	}
+	return nil
+}
 
 var (
 	// ErrNoHealthy means no healthy proxies left.

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
-}

plugin/forward/setup.go

@@ -8,6 +8,7 @@ import (
 	"github.com/coredns/coredns/core/dnsserver"
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/plugin/metrics"
+	"github.com/coredns/coredns/plugin/pkg/policy"
 	"github.com/coredns/coredns/plugin/pkg/parse"
 	pkgtls "github.com/coredns/coredns/plugin/pkg/tls"
 	"github.com/coredns/coredns/plugin/pkg/transport"
@@ -202,11 +203,11 @@ func parseBlock(c *caddy.Controller, f *Forward) error {
 		}
 		switch x := c.Val(); x {
 		case "random":
-			f.p = &random{}
+			f.p = &policy.Random{}
 		case "round_robin":
-			f.p = &roundRobin{}
+			f.p = &policy.RoundRobin{}
 		case "sequential":
-			f.p = &sequential{}
+			f.p = &policy.Sequential{}
 		default:
 			return c.Errf("unknown policy '%s'", x)
 		}