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Platform.sh supports building and deploying applications written in Elixir. There is no default flavor for the build phase, but you can define it explicitly in your build hook. Platform.sh Elixir images support both committed dependencies and download-on-demand. The underlying Erlang version is 22.0.7.

Supported versions 

Grid Dedicated
  • 1.9
None available

To specify an Elixir container, use the type property in your .platform.app.yaml.

type: 'elixir:1.9'

Platform.sh variables 

Platform.sh exposes relationships and other configuration as environment variables. Most notably, it allows a program to determine at runtime what HTTP port it should listen on and what the credentials are to access other services.

To get the PORT environment variable (the port on which your web application is supposed to listen) you would:

String.to_integer(System.get_env("PORT") || "8888")

Some of the environment variables are in JSON format and are base64 encoded. You would need to import a JSON parsing library such as Jason or Poison to read those. (There is an example for doing this to decode the PLATFORM_RELATIONSHIPS environment variable in the section below.)

Building and running the application 

If you are using Hex to manage your dependencies, it will be necessary to specify a set of environment variables in your .platform.app.yaml file that define the MIX_ENV and SECRET_KEY_BASE, which can be set to the Platform.sh-provided PLATFORM_PROJECT_ENTROPY environment variable:

variables:
    env:
        SECRET_KEY_BASE: $PLATFORM_PROJECT_ENTROPY
        MIX_ENV: 'prod'

Include in your build hook the steps to retrieve a local Hex and rebar, and then run mix do deps.get, deps.compile, compile on your application to build a binary.

hooks:
    build: |
        mix local.hex --force
        mix local.rebar --force
        mix do deps.get --only prod, deps.compile, compile

Assuming mix.exs is present at the root of your repository and your build hook matches the above, you can then start it from the web.commands.start directive.

The following basic .platform.app.yaml file is sufficient to run most Elixir applications.

name: app

type: elixir:1.9

variables:
    env:
        MIX_ENV: 'prod'
        SECRET_KEY_BASE: $PLATFORM_PROJECT_ENTROPY

hooks:
    build: |
        mix local.hex --force
        mix local.rebar --force
        mix do deps.get --only prod, deps.compile, compile

web:
    commands:
        start: mix run --no-halt
    locations:
        /:
            allow: false
            passthru: true

Note that there will still be an Nginx proxy server sitting in front of your application. If desired, certain paths may be served directly by Nginx without hitting your application (for static files, primarily) or you may route all requests to the Elixir application unconditionally, as in the example above.

Dependencies 

The recommended way to handle Elixir dependencies on Platform.sh is using Hex. You can commit a mix.exs file in your repository and the system will download the dependencies in your deps section using the build hook above.

  defp deps do
    [
	  {:platformshconfig, "~> 0.1.0"}
    ]
  end

Accessing Services 

The simplest possible way to go around this is to use the Platform.sh Config Reader library from hex. The libraray source is also available on GitHub.

If you are building a Phoenix app for example, it would suffice to add a database to .platform/services.yaml and a relationship in .platform.app.yaml. Put the lib in your deps and, assuming you renamed the proc.secrets.exs to releases.exs per the Phoenix guide, change:

System.get_env("DATABASE_URL")

to

Platformsh.Config.ecto_dsn_formatter("database")

See Platform.sh Config Reader Documentation for the full API.

Accessing Services Manually 

The services configuration is available in the environment variable PLATFORM_RELATIONSHIPS.

Given a relationship defined in .platform.app.yaml:

relationships:
    postgresdatabase: "dbpostgres:postgresql"

Assuming you have in mix.exs the Poison library to parse JSON:

  defp deps do
    [
      {:poison, "~> 3.0"}
    ]
  end

And assuming you use ecto you could put in config/config.exs:

relationships = Poison.decode!(Base.decode64!(System.get_env("PLATFORM_RELATIONSHIPS")))
[postgresql_config | _tail] = relationships["postgresdatabase"]

config :my_app, Repo,
  database: postgresql_config["path"],
  username: postgresql_config["username"],
  password: postgresql_config["password"],
  hostname: postgresql_config["host"]

and setup Ecto during the deploy hook:

deploy: |
    mix do ecto.setup

Project templates 

Platform.sh offers a number of project templates using the structure described above. It can be used as a starting point or reference for building your own website or web application.

Templates in development.