open-nomad/website/source/docs/operating-a-job/configuring-tasks.html.md

layout	page_title	sidebar_current	description
docs	Configuring Tasks - Operating a Job	docs-operating-a-job-configuring-tasks	Most applications require some kind of configuration. Whether this configuration is provided via the command line or via a configuration file, Nomad has built-in functionality for configuration. This section details two common patterns for configuring tasks.

Configuring Tasks

Most applications require some kind of configuration. The simplest way is via command-line arguments, but often times tasks consume complex configurations via config files. This section explores how to configure Nomad jobs to support many common configuration use cases.

Command-line Arguments

Many tasks accept configuration via command-line arguments that do not change over time.

For example, consider the http-echo server which is a small go binary that renders the provided text as a webpage. The binary accepts two parameters:

• -listen - the address:port to listen on
• -text - the text to render as the HTML page

Outside of Nomad, the server is started like this:

$ http-echo -listen=":5678" -text="hello world"

The Nomad equivalent job file might look something like this:

job "docs" {
  datacenters = ["dc1"]

  group "example" {
    task "server" {
      driver = "exec"

      config {
        command = "/bin/http-echo"
        args = [
          "-listen", ":5678",
          "-text", "hello world",
        ]
      }

      resources {
        network {
          mbits = 10
          port "http" {
            static = "5678"
          }
        }
      }
    }
  }
}

~> This assumes the http-echo binary is already installed and available in the system path. Nomad can also optionally fetch the binary using the artifact resource.

Nomad has many drivers, and most support passing arguments to their tasks via the args parameter. This option also optionally accepts Nomad interpolation. For example, if you wanted Nomad to dynamically allocate a high port to bind the service on instead of relying on a static port for the previous job:

job "docs" {
  datacenters = ["dc1"]

  group "example" {
    task "server" {
      driver = "exec"

      config {
        command = "/bin/http-echo"
        args = [
          "-listen", ":${NOMAD_PORT_http}",
          "-text", "hello world",
        ]
      }

      resources {
        network {
          mbits = 10
          port "http" {}
        }
      }
    }
  }
}

Configuration Files

Not all applications accept their configuration via command-line flags. Sometimes applications accept their configurations using files instead. Nomad supports downloading artifacts prior to launching tasks. This allows shipping of configuration files and other assets that the task needs to run properly.

Here is an example job which pulls down a configuration file as an artifact:

job "docs" {
  datacenters = ["dc1"]

  group "example" {
    task "server" {
      driver = "exec"

      artifact {
        source      = "http://example.com/config.hcl"
        destination = "local/config.hcl"
      }

      config {
        command = "my-app"
        args = [
          "-config", "local/config.hcl",
        ]
      }
    }
  }
}

For more information on the artifact resource, please see the artifact documentation.