ZooKeeper Leader Election Process

The Leader in ZooKeeper is determined through an election algorithm. When a ZooKeeper server (node) starts up, it will try to establish connections with other ZooKeeper servers, and then they will communicate with each other to determine their statuses. In the election algorithm, each node has a number and a logical clock, and nodes will send messages to each other to synchronize clocks and confirm their statuses.

When a node realizes it is the only Leader in the current cluster, it will send a broadcast message to request other nodes to acknowledge its Leader status. The other nodes will compare their logical clocks with the Leader node’s logical clock, and choose the node with the highest clock value as the Leader. If there are multiple nodes with the highest clock values, the node with the highest node ID will be chosen as the Leader.

The purpose of the election algorithm is to ensure that at any given time, there is only one leader in the ZooKeeper cluster to guarantee the consistency and reliability of data. If the current leader node fails or loses connection with the cluster, other nodes will use the election algorithm to choose a new leader to ensure the normal operation of the cluster.