exo.hcl

What's in a manifest?

An exo.hcl file contains project configuration and component definitions. It specifies how Exo orchestrates your development environment.

The .hcl file extension refers to the Hashicorp Configuration Language.

Manifest Location

Exo expects one exo.hcl at the root of each workspace. It is intended to be checked in to version control along with your project source.

Template exo.hcl

exo = "0.1"

components {

  process "web" {
    program = "./run-web-server"
  }

  # ...

}

Blocks

Top-Level

The top-level of an exo.hcl file forms the body of an implicit manifest block with the following attributes and sub-blocks.

Attribute	Description
exo	Specifies a manifest format version constraint. It has the form major.minor.	Required

Block	Description
environment	Supplies environment variables used by components.
components	Defines components.

environment Block

Placement: top-level

The environment block supplies environment variables for use by component definitions in the project. For simple key/value string pairs, variables can be specified as attributes in the environment block. For more complex cases, including defining secrets, variables are specified by child blocks within the environment block. Later children blocks shadow earlier blocks, which shadow the environment block-level attributes.

Attribute	Description
/[a-z_][a-z0-9_]*/i	Individual environment variable key/value pair.

Block	Description
secrets	Specifies a secrets value to be merged in to the environment.

secrets Block

Placement: environment

secrets {
  source = "https://example.com/secrets/vault"
}

Attribute	Description
source	URL of the secrets vault.

Visit https://secrets.deref.io/ to create a secrets vault.

components Block

Placement: top-level

The components block acts as a container for individual component blocks. Each component has a unique name across the manifest.

Components may come in the form of component blocks or as macro-blocks named after the type of component. For details regarding specific component types and their respective syntax, see Components.

Block	Description
component	Long form for defining a component.
/[a-z][a-z0-9_]*/	Component definiton macro.

component Block

Placement: components

Each component block specifies an individual component.

Generally, it is less verbose to use type-specific component macros. For details regarding component types and their respective syntax, see Components.

Label	Description
Name	Name of this component. Must match /[a-z_]([a-z0-9-]*[a-z0-9])/.

Attribute	Description
type	Type name for the component to be constructed.	Required
spec	String that defines the component. The format of a spec is dependent on the component's type.	Required if a spec Block is not provided.

spec Block

Placement: component

Alternative to the spec attribute. Specifies a component's configuration in HCL format, instead of as an arbitrary string. The contents of a spec block are entirely dependent on the type of a component.

Resources

• HCL Syntax Specification