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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: 

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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; 

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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. 

