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The discovery and cluster formation processes are responsible for discovering nodes, electing a master, forming a cluster, and publishing the cluster state each time it changes.
The following processes and settings are part of discovery and cluster formation:
Discovery : Discovery is the process where nodes find each other when the master is unknown, such as when a node has just started up or when the previous master has failed.
Quorum-based decision making : How {{es}} uses a quorum-based voting mechanism to make decisions even if some nodes are unavailable.
Voting configurations : How {{es}} automatically updates voting configurations as nodes leave and join a cluster.
Bootstrapping a cluster : Bootstrapping a cluster is required when an {{es}} cluster starts up for the very first time. In development mode, with no discovery settings configured, this is automatically performed by the nodes themselves. As this auto-bootstrapping is inherently unsafe, running a node in production mode requires bootstrapping to be explicitly configured.
Adding and removing master-eligible nodes : It is recommended to have a small and fixed number of master-eligible nodes in a cluster, and to scale the cluster up and down by adding and removing master-ineligible nodes only. However there are situations in which it may be desirable to add or remove some master-eligible nodes to or from a cluster. This section describes the process for adding or removing master-eligible nodes, including the extra steps that need to be performed when removing more than half of the master-eligible nodes at the same time.
Publishing the cluster state : Cluster state publishing is the process by which the elected master node updates the cluster state on all the other nodes in the cluster.
Cluster fault detection : {{es}} performs health checks to detect and remove faulty nodes.
Settings : There are settings that enable users to influence the discovery, cluster formation, master election and fault detection processes.