meta Block

The meta block allows for user-defined arbitrary key-value pairs. It is possible to use the meta block at the job, group, or task level.

job "docs" {
  meta {
    my-key = "my-value"
  }

  group "example" {
    meta {
      my-key = "my-value"
    }

    task "server" {
      meta {
        my-key = "my-value"
      }
    }
  }
}

Metadata is merged up the job specification, so metadata defined at the job level applies to all groups and tasks within that job. Metadata defined at the group layer applies to all tasks within that group.

Meta values are made available inside tasks as runtime environment variables.

meta Parameters

The "parameters" for the meta block can be any key-value. The keys and values are both of type string, but they can be specified as other types. They will automatically be converted to strings. Any character in a key other than [A-Za-z0-9_.] will be converted to _.

meta Examples

The following examples only show the meta blocks. Remember that the meta block is only valid in the placements listed above.

Coercion

This example shows the different ways to specify key-value pairs. Internally, these values will be stored as their string representation. No type information is preserved.

meta {
  key = "true"
  key = true

  key = 1.4
  key = "1.4"
}

Interpolation

This example shows using Nomad interpolation to populate environment variables.

meta {
  class = "${node.class}"
}

Meta keys with dots

Meta keys that aren't valid HCLv2 identifiers, like ones containing ., require an alternative map assignment syntax.

meta = {
  "project.team" = "sre"
}

meta Usage Examples

Templates

To make use of a meta value in a template, refer to its environment variable form.

template {
  destination = "local/out.txt"
  data = <<EOH
  {{ env "NOMAD_META_mykey" }}
EOH
}