134 lines
4 KiB
Markdown
134 lines
4 KiB
Markdown
---
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layout: "docs"
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page_title: "Job Specification"
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sidebar_current: "docs-job-specification-syntax"
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description: |-
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Learn about the Job specification used to submit jobs to Nomad.
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---
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# Job Specification
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The Nomad job specification (or "jobspec" for short) defines the schema for
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Nomad jobs. Nomad jobs are specified in [HCL][], which aims to strike a balance
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between human readable and editable, and machine-friendly.
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The job specification is broken down into smaller pieces, which you will find
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expanded in the navigation menu. We recommend getting started at the [job][]
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stanza. Alternatively, you can keep reading to see a few examples.
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For machine-friendliness, Nomad can also read JSON-equivalent configurations. In
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general, we recommend using the HCL syntax.
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The general hierarchy for a job is:
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```text
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job
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\_ group
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\_ task
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```
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Each job file has only a single job, however a job may have multiple groups, and
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each group may have multiple tasks. Groups contain a set of tasks that are
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co-located on a machine.
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## Example
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This example shows a sample job file. We tried to keep it as simple as possible,
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while still showcasing the power of Nomad. For a more detailed explanation of
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any of these fields, please use the navigation to dive deeper.
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```hcl
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# This declares a job named "docs". There can be exactly one
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# job declaration per job file.
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job "docs" {
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# Specify this job should run in the region named "us". Regions
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# are defined by the Nomad servers' configuration.
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region = "us"
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# Spread the tasks in this job between us-west-1 and us-east-1.
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datacenters = ["us-west-1", "us-east-1"]
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# Run this job as a "service" type. Each job type has different
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# properties. See the documentation below for more examples.
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type = "service"
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# Specify this job to have rolling updates, two-at-a-time, with
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# 30 second intervals.
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update {
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stagger = "30s"
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max_parallel = 1
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}
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# A group defines a series of tasks that should be co-located
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# on the same client (host). All tasks within a group will be
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# placed on the same host.
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group "webs" {
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# Specify the number of these tasks we want.
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count = 5
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# Create an individual task (unit of work). This particular
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# task utilizes a Docker container to front a web application.
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task "frontend" {
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# Specify the driver to be "docker". Nomad supports
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# multiple drivers.
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driver = "docker"
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# Configuration is specific to each driver.
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config {
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image = "hashicorp/web-frontend"
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}
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# The service block tells Nomad how to register this service
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# with Consul for service discovery and monitoring.
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service {
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# This tells Consul to monitor the service on the port
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# labled "http". Since Nomad allocates high dynamic port
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# numbers, we use labels to refer to them.
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port = "http"
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check {
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type = "http"
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path = "/health"
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interval = "10s"
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timeout = "2s"
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}
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}
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# It is possible to set environment variables which will be
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# available to the job when it runs.
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env {
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"DB_HOST" = "db01.example.com"
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"DB_USER" = "web"
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"DB_PASS" = "loremipsum"
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}
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# Specify the maximum resources required to run the job,
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# include CPU, memory, and bandwidth.
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resources {
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cpu = 500 # MHz
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memory = 128 # MB
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network {
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mbits = 100
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# This requests a dynamic port named "http". This will
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# be something like "46283", but we refer to it via the
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# label "http".
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port "http" {}
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# This requests a static port on 443 on the host. This
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# will restrict this task to running once per host, since
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# there is only one port 443 on each host.
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port "https" {
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static = 443
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}
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}
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}
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}
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}
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}
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```
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[hcl]: https://github.com/hashicorp/hcl "HashiCorp Configuration Language"
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[job]: /docs/job-specification/job.html "Nomad job Job Specification"
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