Make sure to drain body upon an error (#7197)

Also cleanup redundant code and use it at a common place

cmd/rpc/client.go

@@ -22,8 +22,6 @@ import (
 	"encoding/gob"
 	"errors"
 	"fmt"
-	"io"
-	"io/ioutil"
 	"net"
 	"net/http"
 	"reflect"
@@ -42,28 +40,6 @@ type Client struct {
 	serviceURL *xnet.URL
 }
 
-// closeResponse close non nil response with any response Body.
-// convenient wrapper to drain any remaining data on response body.
-//
-// Subsequently this allows golang http RoundTripper
-// to re-use the same connection for future requests.
-func closeResponse(body io.ReadCloser) {
-	// Callers should close resp.Body when done reading from it.
-	// If resp.Body is not closed, the Client's underlying RoundTripper
-	// (typically Transport) may not be able to re-use a persistent TCP
-	// connection to the server for a subsequent "keep-alive" request.
-	if body != nil {
-		// Drain any remaining Body and then close the connection.
-		// Without this closing connection would disallow re-using
-		// the same connection for future uses.
-		//  - http://stackoverflow.com/a/17961593/4465767
-		bufp := b512pool.Get().(*[]byte)
-		defer b512pool.Put(bufp)
-		io.CopyBuffer(ioutil.Discard, body, *bufp)
-		body.Close()
-	}
-}
-
 // Call - calls service method on RPC server.
 func (client *Client) Call(serviceMethod string, args, reply interface{}) error {
 	replyKind := reflect.TypeOf(reply).Kind()
@@ -93,7 +69,7 @@ func (client *Client) Call(serviceMethod string, args, reply interface{}) error
 	if err != nil {
 		return err
 	}
-	defer closeResponse(response.Body)
+	defer xhttp.DrainBody(response.Body)
 
 	if response.StatusCode != http.StatusOK {
 		return fmt.Errorf("%v rpc call failed with error code %v", serviceMethod, response.StatusCode)