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Glossary
Terms used in etcd documentation, command line, and source code
This document defines the various terms used in etcd documentation, command line and source code.
Alarm
The etcd server raises an alarm whenever the cluster needs operator intervention to remain reliable.
Client
A client connects to the etcd cluster to issue service requests such as fetching key-value pairs, writing data, or watching for updates.
Cluster
Cluster consists of several members.
The node in each member follows raft consensus protocol to replicate logs. Cluster receives proposals from members, commits them and apply to local store.
Compaction
Compaction discards all etcd event history and superseded keys prior to a given revision. It is used to reclaim storage space in the etcd backend database.
Election
The etcd cluster holds elections among its members to choose a leader as part of the raft consensus protocol.
Key range
A set of keys containing either an individual key, a lexical interval for all x such that a < x ⇐ b, or all keys greater than a given key.
Proposal
A proposal is a request (for example a write request, a configuration change request) that needs to go through raft protocol.
Quorum
The number of active members needed for consensus to modify the cluster state. etcd requires a member majority to reach quorum.
Revision
A 64-bit cluster-wide counter that starts at 1 and is incremented each time the keyspace is modified.
Role
A unit of permissions over a set of key ranges which may be granted to a set of users for access control.
Transaction
An atomically executed set of operations. All modified keys in a transaction share the same modification revision.
Key Version
The number of writes to a key since it was created, starting at 1. The version of a nonexistent or deleted key is 0.