chore: import upstream snapshot with attribution

selector/strategy.go

@@ -0,0 +1,51 @@
+package selector
+
+import (
+	"math/rand"
+	"sync"
+
+	"go-micro.dev/v6/registry"
+)
+
+// Random is a random strategy algorithm for node selection.
+func Random(services []*registry.Service) Next {
+	nodes := make([]*registry.Node, 0, len(services))
+
+	for _, service := range services {
+		nodes = append(nodes, service.Nodes...)
+	}
+
+	return func() (*registry.Node, error) {
+		if len(nodes) == 0 {
+			return nil, ErrNoneAvailable
+		}
+
+		i := rand.Int() % len(nodes)
+		return nodes[i], nil
+	}
+}
+
+// RoundRobin is a roundrobin strategy algorithm for node selection.
+func RoundRobin(services []*registry.Service) Next {
+	nodes := make([]*registry.Node, 0, len(services))
+
+	for _, service := range services {
+		nodes = append(nodes, service.Nodes...)
+	}
+
+	var i = rand.Int()
+	var mtx sync.Mutex
+
+	return func() (*registry.Node, error) {
+		if len(nodes) == 0 {
+			return nil, ErrNoneAvailable
+		}
+
+		mtx.Lock()
+		node := nodes[i%len(nodes)]
+		i++
+		mtx.Unlock()
+
+		return node, nil
+	}
+}