WIP: draft for hash selector

doh-client/client.go

@@ -192,7 +192,25 @@ func NewClient(conf *config.Config) (c *Client, err error) {
 		}
 
 		c.selector = s
-
+	case config.Hash:
+	    if c.conf.Other.Verbose {
+		log.Println(config.Random, "mode start")
+	    }
+	    s := selector.NewHashSelector()
+	    for _, u := range c.conf.Upstream.UpstreamGoogle {
+		if err := s.Add(u.URL, selector.Google); err != nil {
+		    return nil, err
+		}
+	    }
+
+	    for _, u := range c.conf.Upstream.UpstreamIETF {
+		if err := s.Add(u.URL, selector.IETF); err != nil {
+		    return nil, err
+		}
+	    }
+
+	    c.selector = s
+
 	default:
 		if c.conf.Other.Verbose {
 			log.Println(config.Random, "mode start")

doh-client/config/config.go

@@ -33,6 +33,7 @@ const (
 	Random   = "random"
 	NginxWRR = "weighted_round_robin"
 	LVSWRR   = "lvs_weighted_round_robin"
+	Hash   = "hostname_hash"
 )
 
 type upstreamDetail struct {

doh-client/selector/hashSelector.go

@@ -0,0 +1,54 @@
+package selector
+
+import (
+	"errors"
+	"math/rand"
+	"time"
+)
+
+func init() {
+	rand.Seed(time.Now().UnixNano())
+}
+
+type HashSelector struct {
+	upstreams []*Upstream
+}
+
+func NewHashSelector() *HashSelector {
+	return new(HashSelector)
+}
+
+func (rs *HashSelector) Add(url string, upstreamType UpstreamType) (err error) {
+	switch upstreamType {
+	case Google:
+		rs.upstreams = append(rs.upstreams, &Upstream{
+			Type:        Google,
+			URL:         url,
+			RequestType: "application/dns-json",
+		})
+
+	case IETF:
+		rs.upstreams = append(rs.upstreams, &Upstream{
+			Type:        IETF,
+			URL:         url,
+			RequestType: "application/dns-message",
+		})
+
+	default:
+		return errors.New("unknown upstream type")
+	}
+
+	return nil
+}
+
+func (rs *HashSelector) Get() *Upstream {
+    // here, if we have the name to be resolved (a string)
+    // we could compute the modulo over the size of upstream servers
+    // something like url.hash()%len(rs.upstreams)
+    // how to refactor Get() to get the name
+	return rs.upstreams[url.hash()%len(rs.upstreams)]
+}
+
+func (rs *HashSelector) StartEvaluate() {}
+
+func (rs *HashSelector) ReportUpstreamStatus(upstream *Upstream, upstreamStatus upstreamStatus) {}