clientv3: add keep-alive to connection

this makes the grpc client connection use a keep-alive.

clientv3/client.go

@@ -31,6 +31,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/keepalive"
 	"google.golang.org/grpc/metadata"
 )
 
@@ -215,6 +216,16 @@ func (c *Client) dialSetupOpts(endpoint string, dopts ...grpc.DialOption) (opts
 	if c.cfg.DialTimeout > 0 {
 		opts = []grpc.DialOption{grpc.WithTimeout(c.cfg.DialTimeout)}
 	}
+	if c.cfg.DialKeepAliveTime > 0 {
+		params := keepalive.ClientParameters{
+			Time: c.cfg.DialKeepAliveTime,
+		}
+		// Only relevant when KeepAliveTime is non-zero
+		if c.cfg.DialKeepAliveTimeout > 0 {
+			params.Timeout = c.cfg.DialKeepAliveTimeout
+		}
+		opts = append(opts, grpc.WithKeepaliveParams(params))
+	}
 	opts = append(opts, dopts...)
 
 	f := func(host string, t time.Duration) (net.Conn, error) {

clientv3/config.go

@@ -33,6 +33,14 @@ type Config struct {
 	// DialTimeout is the timeout for failing to establish a connection.
 	DialTimeout time.Duration `json:"dial-timeout"`
 
+	// DialKeepAliveTime is the time in seconds after which client pings the server to see if
+	// transport is alive.
+	DialKeepAliveTime time.Duration `json:"dial-keep-alive-time"`
+
+	// DialKeepAliveTimeout is the time in seconds that the client waits for a response for the
+	// keep-alive probe.  If the response is not received in this time, the connection is closed.
+	DialKeepAliveTimeout time.Duration `json:"dial-keep-alive-timeout"`
+
 	// TLS holds the client secure credentials, if any.
 	TLS *tls.Config