To monitor a node in such a manner that an increase in a CPU load in each node required for the monitoring of a node can be suppressed, and an increase in the number of heartbeat messages flowing through a network can be suppressed in a cluster system.

Each of the plurality of nodes includes: a cluster control means 1104 having node configurations 1108, 1208, and 1308 uniquely defined by all nodes. The cluster control means 1104 monitors the adjacent node by logically arranging the plurality of nodes configuring a cluster system like a ring based on the node configuration information, and mutually transmitting/receiving a heartbeat message between the cluster control means of only the two adjacent nodes. When the heartbeat message from the adjacent node can not be received for a prescribed time or more, the cluster control means 1104 determines that any obstacle has been generated in the node.

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