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Merge pull request #6531 from sinsharat/glossary_update

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Documentation/learning: Glossary update
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Gyu-Ho Lee 2016-09-28 11:39:02 -07:00 committed by GitHub
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Documentation/learning/glossary.md
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This document defines the various terms used in etcd documentation, command line and source code.
## Node
## Alarm
Node is an instance of raft state machine.
The etcd server raises an alarm whenever the cluster needs operator intervention to remain reliable.
It has a unique identification, and records other nodes' progress internally when it is the leader.
## Authentication
## Member
Authentication manages user access permissions for etcd resources.
Member is an instance of etcd. It hosts a node, and provides service to clients.
## 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
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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Compaction discards all etcd event history and superseded keys prior to a given revision.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.
## Endpoint
A URL pointing to an etcd service or resource.
## Key
A user-defined identifier for storing and retrieving user-defined values in etcd.
## 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.
## Keyspace
The set of all keys in an etcd cluster.
## Lease
A short-lived renewable contract that deletes keys associated with it on its expiry.
## Member
A logical etcd server that participates in serving an etcd cluster.
## Modification Revision
The first revision to hold the last write to a given key.
## Peer
Peer is another member of the same cluster.
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A proposal is a request (for example a write request, a configuration change request) that needs to go through raft protocol.
## Client
## Quorum
Client is a caller of the cluster's HTTP API.
The number of active members needed for consensus to modify the cluster state. etcd requires a member majority to reach quorum.
## Machine (deprecated)
## Revision
The alternative of Member in etcd before 2.0
A 64-bit cluster-wide counter that 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.
## Snapshot
A point-in-time backup of the etcd cluster state.
## Store
The physical storage backing the cluster keyspace.
## 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.
## Watcher
A client opens a watcher to observe updates on a given key range.