code: def refresh_datasources(self, refreshAll=True):
          
          session = db.session()
          DruidCluster = ConnectorRegistry.sources['druid'].cluster_class
          for cluster in session.query(DruidCluster).all():
              cluster_name = cluster.cluster_name
              valid_cluster = True
              try:
                  cluster.refresh_datasources(refreshAll=refreshAll)
              except Exception as e:
                  valid_cluster = False
                  flash(
                      "Error while processing cluster '{}'\n{}".format(
                          cluster_name, utils.error_msg_from_exception(e)),
                      'danger')
                  logging.exception(e)
                  pass
              if valid_cluster:
                  cluster.metadata_last_refreshed = datetime.now()
                  flash(
                      _('Refreshed metadata from cluster [{}]').format(
                          cluster.cluster_name),
                      'info')
          session.commit()
          return redirect('/druiddatasourcemodelview/list/')
docs: endpoint that refreshes druid datasources metadata