Variable Interpolation

task "docs" {
  driver = "docker"

  # Drivers support interpreting node attributes and runtime environment
  # variables
  config {
    image = "my-app"

    # Interpret runtime variables to inject the address to bind to and the
    # location to write logs to.
    args = [
      "--bind", "${NOMAD_ADDR_RPC}",
      "--logs", "${NOMAD_ALLOC_DIR}/logs",
    ]

    port_map {
      RPC = 6379
    }
  }

  # Constraints only support node attributes as runtime environment variables
  # are only defined after the task is placed on a node.
  constraint {
    attribute = "${attr.kernel.name}"
    value     = "linux"
  }

  template {
    destination = "template.txt"
    data = <<EOT
{{- /*
      Environment variables are available to templates via the env function,
      rather than the ${...} syntax.
*/ -}}
Running on {{env "attr.unique.hostname"}}.
EOT
  }

  # Environment variables are interpreted and can contain both runtime and
  # node attributes. These environment variables are passed into the task.
  env {
    DC      = "Running on datacenter ${node.datacenter}"
    VERSION = "Version ${NOMAD_META_VERSION}"
  }

  # Meta keys are also interpretable.
  meta {
    VERSION = "v0.3"
  }
}

job "docs" {
  # This will constrain this job to only run on 64-bit clients.
  constraint {
    attribute = "${attr.cpu.arch}"
    value     = "amd64"
  }

  # This will restrict the job to only run on clients with 4 or more cores.
  # Note: you may also declare a resource requirement for CPU for a task.
  constraint {
    attribute = "${cpu.numcores}"
    operator  = ">="
    value     = "4"
  }

  # Only run this job on a memory-optimized AWS EC2 instance.
  constraint {
    attribute = "${attr.platform.aws.instance-type}"
    value     = "m4.xlarge"
  }
}

job "sample" {
  datacenters = ["dc1"]
  group "g1" {
    task "redis" {

      # Note: to set an environment variable with an invalid name, you must
      # use the HCL2 map assignment syntax for `env`. Otherwise, the job spec
      # parser will throw an `Argument or block definition required` error
      env = {
        "invalid...name" = "value1"
        "valid.name"     = "value2"
      }

      driver = "docker"
      config {
        image  = "redis:7"
        labels {
          label1 = "${env["invalid...name"]}"
          label2 = "${valid.name}"
        }
      }
    }
  }
}