[skip ci] Add comment for datanode Client (#12804)

Signed-off-by: Nshaoyue.chen <shaoyue.chen@zilliz.com>

internal/distributed/datanode/client/client.go

@@ -87,6 +87,7 @@ func (c *Client) getAddr() (string, error) {
 	return c.addr, nil
 }
 
+// GetComponentStates returns ComponentStates
 func (c *Client) GetComponentStates(ctx context.Context) (*internalpb.ComponentStates, error) {
 	ret, err := c.grpcClient.ReCall(ctx, func(client interface{}) (interface{}, error) {
 		if !funcutil.CheckCtxValid(ctx) {
@@ -150,6 +151,7 @@ func (c *Client) FlushSegments(ctx context.Context, req *datapb.FlushSegmentsReq
 	return ret.(*commonpb.Status), err
 }
 
+// GetMetrics returns metrics
 func (c *Client) GetMetrics(ctx context.Context, req *milvuspb.GetMetricsRequest) (*milvuspb.GetMetricsResponse, error) {
 	ret, err := c.grpcClient.ReCall(ctx, func(client interface{}) (interface{}, error) {
 		if !funcutil.CheckCtxValid(ctx) {
@@ -163,6 +165,7 @@ func (c *Client) GetMetrics(ctx context.Context, req *milvuspb.GetMetricsRequest
 	return ret.(*milvuspb.GetMetricsResponse), err
 }
 
+// Compaction return compaction by given plan
 func (c *Client) Compaction(ctx context.Context, req *datapb.CompactionPlan) (*commonpb.Status, error) {
 	ret, err := c.grpcClient.ReCall(ctx, func(client interface{}) (interface{}, error) {
 		if !funcutil.CheckCtxValid(ctx) {