fix(registry/polaris): fix concurrent map iteration and map write #3361

contrib/polaris/registry.go

@@ -115,15 +115,16 @@ func (r *Registry) Register(_ context.Context, instance *registry.ServiceInstanc
 		}
 
 		// metadata
-		if instance.Metadata == nil {
-			instance.Metadata = make(map[string]string)
+		rmd := mapClone(instance.Metadata)
+		if rmd == nil {
+			rmd = make(map[string]string)
 		}
-		instance.Metadata["merge"] = id
-		if _, ok := instance.Metadata["weight"]; !ok {
-			instance.Metadata["weight"] = strconv.Itoa(r.opt.Weight)
+		rmd["merge"] = id
+		if _, ok := rmd["weight"]; !ok {
+			rmd["weight"] = strconv.Itoa(r.opt.Weight)
 		}
 
-		weight, _ := strconv.Atoi(instance.Metadata["weight"])
+		weight, _ := strconv.Atoi(rmd["weight"])
 
 		_, err = r.provider.RegisterInstance(
 			&polaris.InstanceRegisterRequest{
@@ -378,3 +379,18 @@ func instancesToServiceInstances(instances map[string][]model.Instance) []*regis
 	}
 	return serviceInstances
 }
+
+// Clone returns a copy of m.  This is a shallow clone:
+// the new keys and values are set using ordinary assignment.
+func mapClone[M ~map[K]V, K comparable, V any](m M) M {
+	// Preserve nil in case it matters.
+	if m == nil {
+		return nil
+	}
+	// Make a shallow copy of the map.
+	m2 := make(M, len(m))
+	for k, v := range m {
+		m2[k] = v
+	}
+	return m2
+}

contrib/polaris/registry_test.go

@@ -2,6 +2,7 @@ package polaris
 
 import (
 	"context"
+	"strconv"
 	"testing"
 	"time"
 
@@ -28,6 +29,9 @@ func TestRegistry(t *testing.T) {
 		WithRegistryTTL(1000),
 	)
 
+	mm := map[string]string{
+		"test1": "test1",
+	}
 	ins := &registry.ServiceInstance{
 		ID:      "test-ut",
 		Name:    "test-ut",
@@ -36,8 +40,19 @@ func TestRegistry(t *testing.T) {
 			"grpc://127.0.0.1:8080",
 			"http://127.0.0.1:9090",
 		},
+		Metadata: mm,
 	}
 
+	go func() {
+		for i := 0; true; i++ {
+			str := "test" + strconv.Itoa(i)
+			_ = mm[str]
+			if i > 100 {
+				i = 0
+			}
+		}
+	}()
+
 	err = r.Register(context.Background(), ins)
 
 	t.Cleanup(func() {