notes/IT/Hashicorp Nomad.md

# Terminology
## Cluster Terms

| Phrase      | Definition                                                                                                                                                                                                     |
| ----------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| agent       | A process running in server or client mode.                                                                                                                                                                    |
| client/node | A Nomad client is responsible for running tasks assigned to it. A client registers itself with servers and watches for work to be assigned. When running the agent, the client may be referred to as a *node*. |
| server      | A Nomad server manages all jobs and clients, monitors tasks, and controls which tasks get placed on which nodes.                                                                                               |
| dev_agent   | The development agent is an agent configuration that provides useful defaults for running a single node cluster of nomad.                                                                                      |

## Work terms
| Phrase                    | Definition                                                                                                                                                                                                                                                                        |
| ------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| task                      | The smallest unit of work in Nomad. Tasks are executed by task drivers like `docker` or `exec`, which allows Nomad to be flexible in the types of tasks it supports. Tasks specify their required task driver, configuration for the driver, constraints, and resources required. |
| group                     | A series of tasks that run on the same Nomad client.                                                                                                                                                                                                                              |
| job                       | The core unit of *control* for Nomad and defines the application and its configuration. It can contain one or many tasks                                                                                                                                                          |
| job_specification/jobspec | A job specification, also known as a jobspec.                                                                                                                                                                                                                                     |
| allocation                | An allocation is a mapping between a task group in a job and a client node. When a job is run, Nomad will chose a client capable of running it and allocates resources on the machine for the ask(s) in the task group defined for the job.                                       |