ndbinfo: The NDB Cluster Information Database left_node  and  right_node  are defined in terms of a model that connects all data nodes in a circle, in order of their node IDs, similar to the ordering of the numbers on a clock dial, as shown here: Figure 23.27 Circular Arrangement of NDB Cluster Nodes In this example, we have 8 data nodes, numbered 5, 6, 7, 8, 12, 13, 14, and 15, ordered clockwise in a circle. We determine “left”  and “right”  from the interior of the circle. The node to the left of node 5 is node 15, and the node to the right of node 5 is node 6. You can see all these relationships by running the following query and observing the output: mysql>  SELECT node_id,left_node,right_node ->  FROM ndbinfo.membership; +---------+-----------+------------+ | node_id | left_node | right_node | +---------+-----------+------------+ | 5 | 15 | 6 | | 6 | 5 | 7 | | 7 | 6 | 8 | | 8 | 7 | 12 | | 12 | 8 | 13 | | 13 | 12 | 14 | | 14 | 13 | 15 | | 15 | 14 | 5 | +---------+-----------+------------+ 8 rows in set (0.00 sec) The designations “left”  and “right”  are used in the event log in the same way. The  president  node is the node viewed by the current node as responsible for setting an arbitrator (see NDB Cluster Start Phases). If the president fails or becomes disconnected, the current node expects the node whose ID is shown in the  successor  column to become the new president. The succession_order  column shows the place in the succession queue that the current node views itself as having. In a normal NDB Cluster, all data nodes should see the same node as  president , and the same node (other than the president) as its  successor . In addition, the current president should see itself as  1  in the order of succession, the  successor  node should see itself as  2 , and so on. All nodes should show the same  arb_ticket  values as well as the same  arb_state  values. Possible arb_state  values are  ARBIT_NULL ,  ARBIT_INIT ,  ARBIT_FIND ,  ARBIT_PREP1 ,  ARBIT_PREP2 , ARBIT_START ,  ARBIT_RUN ,  ARBIT_CHOOSE ,  ARBIT_CRASH , and  UNKNOWN . arb_connected  shows whether this node is connected to the node shown as this node’s  arbitrator . The  connected_rank1_arbs  and  connected_rank2_arbs  columns each display a list of 0 or more arbitrators having an  ArbitrationRank  equal to 1, or to 2, respectively. 4562