clientv3: add DialNoWait to Config for non-blocking New()

Fixes etcd-io#6162

clientv3/client.go

@@ -138,11 +138,13 @@ func (c *Client) dialTarget(endpoint string) (proto string, host string, creds *
 	return
 }
 
-// dialSetupOpts gives the dial opts prioer to any authentication
-func (c *Client) dialSetupOpts(endpoint string, dopts ...grpc.DialOption) []grpc.DialOption {
-	opts := []grpc.DialOption{
-		grpc.WithBlock(),
-		grpc.WithTimeout(c.cfg.DialTimeout),
+// dialSetupOpts gives the dial opts prior to any authentication
+func (c *Client) dialSetupOpts(endpoint string, dopts ...grpc.DialOption) (opts []grpc.DialOption) {
+	if c.cfg.DialTimeout > 0 {
+		opts = append(opts, grpc.WithTimeout(c.cfg.DialTimeout))
+	}
+	if !c.cfg.DialNoWait {
+		opts = append(opts, grpc.WithBlock())
 	}
 	opts = append(opts, dopts...)
 

clientv3/client_test.go

@@ -56,6 +56,15 @@ func TestDialTimeout(t *testing.T) {
 	}
 }
 
+func TestDialNoWait(t *testing.T) {
+	cfg := Config{Endpoints: []string{"foo:12345"}, DialNoWait: true}
+	c, err := New(cfg)
+	if c == nil || err != nil {
+		t.Fatalf("new client with DialNoWait should succeed, got %v", err)
+	}
+	c.Close()
+}
+
 func TestIsHaltErr(t *testing.T) {
 	if !isHaltErr(nil, fmt.Errorf("etcdserver: some etcdserver error")) {
 		t.Errorf(`error prefixed with "etcdserver: " should be Halted by default`)

clientv3/config.go

@@ -31,6 +31,9 @@ type Config struct {
 	// DialTimeout is the timeout for failing to establish a connection.
 	DialTimeout time.Duration
 
+	// DialNoWait, when true, returns a Client before establishing a connection.
+	DialNoWait bool
+
 	// TLS holds the client secure credentials, if any.
 	TLS *tls.Config