return an error if the update list is empty, might be a transient err…

…or, logged in discovery

elastictransport/connection.go

@@ -219,6 +219,10 @@ func (cp *statusConnectionPool) OnFailure(c *Connection) error {
 // Update merges the existing live and dead connections with the latest nodes discovered from the cluster.
 // ConnectionPool must be locked before calling.
 func (cp *statusConnectionPool) Update(connections []*Connection) error {
+	if len(connections) == 0 {
+		return errors.New("no connections provided, connection pool left untouched")
+	}
+
 	// Remove hosts that are no longer in the new list of connections
 	for i := 0; i < len(cp.live); i++ {
 		found := false

elastictransport/discovery.go

@@ -109,7 +109,9 @@ func (c *Client) DiscoverNodes() error {
 		if p, ok := c.pool.(UpdatableConnectionPool); ok {
 			err = p.Update(conns)
 			if err != nil {
-				return err
+				if debugLogger != nil {
+					debugLogger.Logf("Error updating pool: %s\n", err)
+				}
 			}
 		} else {
 			c.pool, err = NewConnectionPool(conns, c.selector)