scalingo.json Schema

scalingo.json is a deployment manifest to let people deploy their software super easily. This document describe its schema in detail.

The manifest

This document describes how to write a JSON manifest file which will be interpreted by our platform when someone wants to deploy a project. The file must be located at the root of the project and be named either app.json or scalingo.json. The latter will always take priority over the first one.

This JSON manifest is read when deploying a review app or a one-click deploy.

All attributes are optional.

The manifest attributes

field	type	description
name	string	Complete name of the project
repository	string	Location of the GIT repository of the project
ref	string	Branch name or commit ID of the code to use
stack	string	Name of the stack to use
description	string	Description in one or two sentences of the app
logo	string	URL to the logo of the project
website	string	Official website of the application if any
copy_parent_database_urls	boolean	Copy database credentials from parent app
env	object	Environment of the application, see below
addons	array	List of all the addons required to run the app
scripts	object	Optional hook scripts, see below
formation	object	Formation of containers when an app is created

Environment

The keys of the environment object are the name of the variables you want to add.

field	type	description
`VAR_NAME`	string	key of the object is the name of the env variable

Each of these keys has to respect the following properties:

field	type	description
description	string	Description of the variable to explain what it does
value	string	(if no generator) Default value of the variable
generator	string	(if no value) Use a generator to define a default value
template	string	(if generator is ‘url’ or ‘template’) Template to generate value from
required	boolean	Mandatory to fill the value before deploying the one-click

Note: supplying null or an empty string to value will remove the variable from the environment. It can be used to delete environment variables present in the parent app.

Three generators are available secret, template or url:

secret: generates a unique token as a default value of the variable. Useful for instance when one need to generate a unique encryption seed key, example: 90ffea2d3071e8d86cafb89ff5060883
template: generates an environment variable based on the content of the template field. The following tokens are substituted dynamically by the expected values when surrounded by %:
- APP
- PARENT_APP
- PR_NUMBER
Example: If the review app being deployed is my-app-pr10:
- Pull Request Number %PR_NUMBER% -> Pull Request Number 10
url: automatically inserts the URL of the application after its deployment. When this generator is used, the template property is taken into account, the token %URL% can be used to be replaced by the created app URL.

scalingo.json example

{
  "name": "Sample Go Martini",
  "stack": "scalingo-18",
  "description": "Sample web application using the Go framework Martini",
  "logo": "https://scalingo.com/logo.svg",
  "repository": "https://github.com/Scalingo/sample-go-martini",
  "website": "https://scalingo.com",
  "env": {
    "VAR_TEST_1": {
      "description": "test variable number 1",
      "value": "1"
    },
    "VAR_SECRET_1": {
      "description": "generated variable 1",
      "generator": "secret"
    },
    "PUBLIC_URL": {
      "description": "URL of the application",
      "generator": "url"
    },
    "ADMIN_URL": {
      "description": "Admin URL of the application",
      "generator": "url",
      "template": "%URL%/admin"
    }
  },
  "addons": [
    {
      "plan": "mongodb:mongo-starter-256",
      "options": {
        "version": "4.0.16-1"
      }
    }
  ],
  "scripts": {
    "first-deploy": "echo 'first deployment'",
    "postdeploy": "echo hello"
  },
  "formation": {
    "web": {
      "amount": 1,
      "size": "S"
    },
    "other": {
      "amount": 1,
      "size": "S"
    }
  }
}

Addons

If no addons key is specified, the default behaviour is to duplicate the addons from the parent application.

The addons field contains an array of object describing the addons you need to deploy for your review app. The object must have the following properties:

field	type	description
plan	string	Plan of the addon of the review app
options	object	Various options regarding the addon

The plan uses the format addon-name:plan-id. E.g. mongodb:mongo-starter-256 or redis:redis-sandbox.

The only options field is version which contains the version to deploy (e.g. 4.0.16-1).

Formation

The formation is the definition of the container which will be started once the application is deployed. (Either coming from a one-click deployment button, or a review app from the GitHub integration)

It should be a map of container type definitions, the key should be the type name and the value should have the following structure:

field	type	description
amount	integer	Number of containers to start once the application is deployed
size	string	Container size `name` (get the list of sizes)

Get the default list of sizes on the pricing page.

Scripts

The scripts.postdeploy key is now deprecated in favor of postdeploy hook in the Procfile. More information on the dedicated page.

field	type	description
postdeploy	string	Command and arguments of the script you want to execute after each deployment.
first-deploy	string	Job to run as postdeploy hook at the first deployment of a review app or one-click deployed app

You can get more information on this feature on the dedicated page.

Example

This example comes from a concrete project located on Github.

With the scalingo.json in the above-mentioned project, the example will:

Define the name of the project.
Describe in a sentence the purpose of the project.
Location of the logo.
URL of the GIT repository.
Official website of the project.
List of the environment variables with their description and optional generator VAR_TEST_1 and VAR_SECRET_1. These environment variables will be available for your application.
Ask for the provisioning of a Redis addon.
Execute the provided script after the container booted.