clientv3: add 'CheckHealth' method

Signed-off-by: Gyu-Ho Lee <[email protected]>

clientv3/client.go

@@ -31,6 +31,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
+	healthpb "google.golang.org/grpc/health/grpc_health_v1"
 	"google.golang.org/grpc/metadata"
 )
 
@@ -47,6 +48,7 @@ type Client struct {
 	Watcher
 	Auth
 	Maintenance
+	healthpb.HealthClient
 
 	conn     *grpc.ClientConn
 	dialerrc chan error
@@ -408,6 +410,7 @@ func newClient(cfg *Config) (*Client, error) {
 	client.Watcher = NewWatcher(client)
 	client.Auth = NewAuth(client)
 	client.Maintenance = NewMaintenance(client)
+	client.HealthClient = healthpb.NewHealthClient(client.conn)
 
 	if cfg.RejectOldCluster {
 		if err := client.checkVersion(); err != nil {
@@ -463,6 +466,15 @@ func (c *Client) checkVersion() (err error) {
 // ActiveConnection returns the current in-use connection
 func (c *Client) ActiveConnection() *grpc.ClientConn { return c.conn }
 
+// CheckHealth checks the health status of gRPC server of current connection.
+func (c *Client) CheckHealth(ctx context.Context) (healthpb.HealthCheckResponse_ServingStatus, error) {
+	resp, err := c.HealthClient.Check(ctx, &healthpb.HealthCheckRequest{})
+	if err != nil {
+		return healthpb.HealthCheckResponse_UNKNOWN, err
+	}
+	return resp.Status, err
+}
+
 // isHaltErr returns true if the given error and context indicate no forward
 // progress can be made, even after reconnecting.
 func isHaltErr(ctx context.Context, err error) bool {

clientv3/integration/kv_test.go

@@ -30,8 +30,35 @@ import (
 	"github.com/coreos/etcd/pkg/testutil"
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
+	healthpb "google.golang.org/grpc/health/grpc_health_v1"
 )
 
+func TestHealth(t *testing.T) {
+	defer testutil.AfterTest(t)
+
+	clus := integration.NewClusterV3(t, &integration.ClusterConfig{Size: 1})
+	defer clus.Terminate(t)
+
+	cli := clus.RandClient()
+	st, err := cli.CheckHealth(context.TODO())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if st != healthpb.HealthCheckResponse_SERVING {
+		t.Fatalf("status expected %s, got %s", healthpb.HealthCheckResponse_SERVING, st)
+	}
+
+	clus.TerminateMember(t, 0)
+
+	st, err = cli.CheckHealth(context.TODO())
+	if st != healthpb.HealthCheckResponse_UNKNOWN {
+		t.Fatalf("status expected %s, got %s", healthpb.HealthCheckResponse_UNKNOWN, st)
+	}
+	if grpc.ErrorDesc(err) != "there is no address available" {
+		t.Fatalf("error expected 'there is no address available', got %v", err)
+	}
+}
+
 func TestKVPutError(t *testing.T) {
 	defer testutil.AfterTest(t)