Deploying Phoenix Projects with Distillery on Render

This is a guide to deploying Phoenix projects on Render using Distillery.

We'll start off with a bare Phoenix project with Ecto, modify it to use Distillery, and deploy it on Render. The full source code for this tutorial is available at GitHub.

Create a Phoenix App with Distillery

1. Create a new Phoenix app in the terminal:

   $ mix phx.new phoenix_distillery # also fetch and install dependencies
   $ cd phoenix_distillery

2. Update mix.exs to add Distillery to deps:

   defp deps do
       [ ...,\
         {:distillery, "~> 2.0"}\
       ]
   end

Then run mix deps.get in your terminal to update dependencies.

Configure Distillery

1. Let's configure Distillery for production. Update the Endpoint config in config/prod.exs so it looks like this:

   config :phoenix_distillery, PhoenixDistilleryWeb.Endpoint,
         cache_static_manifest: "priv/static/cache_manifest.json",
         server: true, # critical for Phoenix to run
         root: ".",
         version: Application.spec(:phoenix_distillery, :vsn)

Read more about Distillery configuration.

We're not going to check secrets into source control. Instead, we're going to manage them in production with Render environment variables. So let's delete the line at the end referring to prod.secret.exs.

   import_config "prod.secret.exs" # delete me

And delete the file config/prod.secret.exs.

2. You're now ready to initialize your Distillery release.

   $ mix distillery.init

This will create rel/config.exs, rel/vm.args, and the empty directory rel/plugins.

rel/vm.args is used for runtime configuration by default, but we're going to use the Mix Config Provider instead so you can delete this file.

Creating a Mix Config Provider

1. Create a Mix configuration file at rel/config/config.exs:

   $ mkdir -p rel/config
   

   Contents of rel/config/config.exs :

   use Mix.Config
   
   port = String.to_integer(System.get_env("PORT") || "4000")
   default_secret_key_base = :crypto.strong_rand_bytes(43) |> Base.encode64
   
   config :phoenix_distillery, PhoenixDistilleryWeb.Endpoint,
         http: [port: port],
         url: [host: "localhost", port: port],
         secret_key_base: System.get_env("SECRET_KEY_BASE") || default_secret_key_base
   

   This sets up the Mix configuration provider to get values from runtime environment variables.

2. Update rel/config.exs to use your new provider. Change the environment :prod section in the file to this:

   environment :prod do
         set include_erts: true
         set include_src: false
         set cookie: :"GZUAPxTBG1]F%gaBG6.|Fxqpi^]dVX>:AFn^YxR/RY%KE1ys/l6$cd3}8r4h$B4E"
         set config_providers: [\
           {Distillery.Releases.Config.Providers.Elixir, ["${RELEASE_ROOT_DIR}/etc/config.exs"]}\
         ]
         set overlays: [\
           {:copy, "rel/config/config.exs", "etc/config.exs"}\
         ]
   end
   

Configuring Ecto

Let's configure Ecto to get the DATABASE_URL from the environment. Change lib/phoenix_distillery/repo.ex so it looks like this:

   defmodule PhoenixDistillery.Repo do
       use Ecto.Repo,
           otp_app: :phoenix_distillery,
           adapter: Ecto.Adapters.Postgres,
           pool_size: 10
   
       def init(_type, config) do
           {:ok, Keyword.put(config, :url, System.get_env("DATABASE_URL"))}
       end
   end

Build a Release with Distillery

You're now ready to build and run your first release!

   $ npm run deploy --prefix assets && MIX_ENV=prod mix do phx.digest, distillery.release --env=prod

The output should look like this:

==> Assembling release..
==> Building release phoenix_distillery:0.1.0 using environment prod
==> Including ERTS 10.4.4 from /usr/local/Cellar/erlang/22.0.7/lib/erlang/erts-10.4.4
==> Packaging release..
Release successfully built!
To start the release you have built, you can use one of the following tasks:

# start a shell, like 'iex -S mix'
> _build/prod/rel/phoenix_distillery/bin/phoenix_distillery console

# start in the foreground, like 'mix run --no-halt'
> _build/prod/rel/phoenix_distillery/bin/phoenix_distillery foreground

# start in the background, must be stopped with the 'stop' command
> _build/prod/rel/phoenix_distillery/bin/phoenix_distillery start

If you started a release elsewhere, and wish to connect to it:

# connects a local shell to the running node
> _build/prod/rel/phoenix_distillery/bin/phoenix_distillery remote_console

# connects directly to the running node's console
> _build/prod/rel/phoenix_distillery/bin/phoenix_distillery attach

For a complete listing of commands and their use:

> _build/prod/rel/phoenix_distillery/bin/phoenix_distillery help

You can now test your release (assuming PostgreSQL is up on your local machine):

   $ export DATABASE_URL=postgresql://username:password@127.0.0.1:5432/phoenix_distillery
   $ _build/prod/rel/phoenix_distillery/bin/phoenix_distillery foreground
   
   12:00:00.123 [info] Running PhoenixDistilleryWeb.Endpoint with cowboy 2.6.1 at http://localhost:4000

You can now deploy your app in production! 🎉

Deploying to Render

1. Create a build script called build.sh at the root of your repo:

   #!/usr/bin/env bash
   # exit on error
   set -o errexit
   
   export MIX_ENV=prod
   
   # get app name and version from mix.exs
   export APP_NAME="$(grep 'app:' mix.exs | sed -e 's/\[//g' -e 's/ //g' -e 's/app://' -e 's/[:,]//g')"\
   export APP_VSN="$(grep 'version:' mix.exs | cut -d '"' -f2)"\
   
   # remove existing builds\
   rm -rf "_build"\
   
   # Compile app and assets\
   mix deps.get --only prod\
   mix compile\
   cd assets && npm install && npm run deploy && cd ..\
   
   # create release\
   # we don't need to create a tarball because the app will be\
   # served directly from the build directory\
   mix do phx.digest, distillery.release --env=prod --no-tar\
   
   echo "Linking release $APP_NAME:$APP_VSN to _render/"\
   
   ln -sf "_build/$MIX_ENV/rel/$APP_NAME" _render

Make the script executable before checking it into Git:

$ chmod a+x build.sh

2. Create a new PostgreSQL database on Render.

3. Create a new Web Service on Render, and give Render permission to access your new repo.

4. Use the following values during creation:

   Language	Elixir
   Build Command	./build.sh
   Start Command	./_render/bin/phoenix_distillery foreground

Also add these environment variables to the web service:

Going forward, every push to your repo will automatically build your app and deploy it in production. If the build fails, Render will automatically stop the deploy process and the existing version of your app will keep running until the next successful deploy.

Read about customizing Elixir and Erlang versions for your app.