Nomad Glossary

Nomad Cluster

agent
- A Nomad agent is a Nomad process running in server or client modem, the basic building block of a Nomad cluster
server
- A Nomad agent running in Server mode, the brains of the cluster
leader
- The leader is a Nomad server that performs the bulk of the cluster management, its in charge of maintaining the cluster state
follower
- Non-leader Nomad servers. Followers create scheduling plans and submit them to the leader to provide more scheduling capacity to the cluster.
client
- A Nomad agent running in client mode. Client agents are responsible for registering themselves with the servers, watching for any work to be assigned, and executing tasks.

job → task group → task

job
- A job defines one or more task groups which contain one or more tasks.
job specification
- The Nomad job specification (or “jobspec” for short) defines the schema for Nomad jobs.
task group
- A set of tasks that must be run together (on the same client node). A running instance of a task group is an allocation
task driver
- A task driver represents the basic means of executing tasks.
task
- The smallest unit of work in Nomad. Tasks are executed by task drivers.
allocation
- The mapping between a task group in a job and a client node. Allocations are created by the Nomad serves as part of scheduling decisions made during an evaluation.
evaluation
- Mechanism by which Nomad makes scheduling decisions, When either the desired state (jobs) or actual state (clients) changes, Nomad creates a new evaluation to determine if any actions must be taken. An evaluation may result in changes to allocations if necessary.