I have been watching Elixir for almost 2 years now, and debating if it’s mature enough for me to invest in.

Obviously Erlang is super-mature, and Elixir is quite stable, but it’s a question of “is the community mature enough yet?”

Since I’m now writing this, I believe it is “ready”, and I’m beginning a journey to build out some services in Elixir to stand up next to existing node services (meteorjs) and slow move funcitonality over to to Elixir.

Chapter One: Proof of Concept, Mongo is supposed to be Simple.

If you’re not already familiar with any of these tools: - [Elixir you should checkout the meteor website If you’re not already familiar with Meteor you should checkout the meteor website Come back to this when you’re comfortable and want to optimize an existing application.


Build an elixir+phoenix application which will connect to an existing MongoDB for an existing MeteorJS/Node application, and expose functionality via a GraphQL API.

  • database and schema un-changeable, must match what is already there, in Mongo
  • authentication must piggyback/use Meteor Accounts
  • permissions must re-implement functionality of Meteor Roles
  • framework = elixir+phoenix (more on why, below)
  • graphql API to be handled via absinthe


GraphQL is badass. It will replace REST, like REST replaced SOAP.

I could make a GraphQL server for an existing Meteor application inside Meteor, or via a node API, or any other server side framework…

But I’ve been watching Elixir for a while and I’m impressed by it’s performace, HA, and syntax. Functional & Parallel. (Dave Thomas Approves)

Getting Started

install elixir

Nothing hard or tricky here…

brew install elixir (for OSX, others for you) and mix

install phoenix

I chose to install phoenix 1.3.0-rc2 because I read up on it and I think it’s got some good changes (in app structure) and likely to land sometime soon-ish.

mix archive.install https://github.com/phoenixframework/archives/raw/master/phoenix_new.ez

build a new phoenix app

Here’s my command:

mix phx.new --no-html --no-brunch --app e2mapi elixir-meteor-graphql

  • --no-html I don’t need serverside rendering
  • --no-brunch I don’t need elixir to build JS packages
  • --app e2mapi I have to give it a “friendly” app name
  • elixir-meteor-graphql My project folder

I can then cd into the dir, (make it a git repo & commit,) then edit the mix.exs file to change deps.

add mongodb_ecto (to connect to Mongo, but with Ecto awesomeness)

This should be as simple as adding in a mix package… But I ran into several problems with versions and mis-matching.

I tried reverting to Phoenix 1.2, I tried various branches and tags of various packages.

After coming up with a stable seeming combination my PR was not accepted and we are told to instead force the core ecto to 2.0.

There is no readme telling us this, and I think it’s a temporary requirement, but it is currently a requirement.

So - here is my mix.exs for mongo + ecto:

     {:mongodb_ecto, github: "michalmuskala/mongodb_ecto", branch: "ecto-2"}, # <-- using mongo
     {:ecto, "~> 2.0", override: true}, # <-- have to FORCE ecto version :(

(likely to change in the future, hopefully towards basic versions)

add absinthe (for GraphQL)

Again this should be simple, but I ran into issues getting the adaptors to play nice, specifically with poison & absinthe_ecto.

Here’s the combination which worked for me, now.

     # Poision 3.+ flags older phoenix ecto -- no breaking changes override:true
     {:poison, "~> 3.1", override: true},
     {:absinthe, "~> 1.3"},
     {:absinthe_ecto, git: "https://github.com/absinthe-graphql/absinthe_ecto.git"},
     {:absinthe_plug, github: "absinthe-graphql/absinthe_plug", branch: "master"}

(likely to change in the future, hopefully towards basic versions)

edit config to get to the database

Ecto should now be able to talk mongo but it does not know who to talk to yet.

Edit config/dev.exs and change the config at the bottom to be something like:

# Configure your database
config :e2mapi, E2mapi.Repo,
  adapter: Mongo.Ecto,
  database: "e2mapi_dev",
  hostname: "localhost"
  port: 27017

get deps & sanity check

At this point, you should be able to get all deps without errors

$ mix deps.get

And you should be able to fire up iex and load your new (empty) phoenix server

$ iex -S mix phx.server

If it worked right you should see something like:

[info] Running E2mapi.Web.Endpoint with Cowboy using
Interactive Elixir (1.4.4) - press Ctrl+C to exit (type h() ENTER for help)

(Can’t connect to mongo? Is mongo running locally? Is the configuration correct?)

extra work for testing

Embrace testing. If you have not already done so, now is your chance.

Elixir makes it super easy to write tests. They are less fragile & more powerful (thanks to elixir syntax). And doctests support is crazy good too.

Sadly, here too, there are extra hoops to jump through in order to get Ecto + Mongo playing nicely.

First, the easy one, we have a test env to config, just like dev.

Edit config/test.exs and change the config at the bottom to be something like:

# Configure your database
config :e2mapi, E2mapi.Repo,
  adapter: Mongo.Ecto,
  database: "e2mapi_test",
  hostname: "localhost"
  port: 27017

After doing so, I started getting errors like the following:

$ mix test
Compiling 12 files (.ex)
Generated e2mapi app
** (RuntimeError) cannot configure sandbox with pool nil.
To use the SQL Sandbox, configure your repository pool as:

      pool: Ecto.Adapters.SQL.Sandbox

    (ecto) lib/ecto/adapters/sql/sandbox.ex:429: Ecto.Adapters.SQL.Sandbox.mode/2
    (elixir) lib/code.ex:370: Code.require_file/2
    (elixir) lib/enum.ex:645: Enum."-each/2-lists^foreach/1-0-"/2
    (elixir) lib/enum.ex:645: Enum.each/2
    (mix) lib/mix/tasks/test.ex:229: Mix.Tasks.Test.run/1

After doing some searching, I found “SQL Sandbox” code in several test files.

$ ag Sandbox
30:    :ok = Ecto.Adapters.SQL.Sandbox.checkout(E2mapi.Repo)
32:      Ecto.Adapters.SQL.Sandbox.mode(E2mapi.Repo, {:shared, self()})

31:    :ok = Ecto.Adapters.SQL.Sandbox.checkout(E2mapi.Repo)
33:      Ecto.Adapters.SQL.Sandbox.mode(E2mapi.Repo, {:shared, self()})

29:    :ok = Ecto.Adapters.SQL.Sandbox.checkout(E2mapi.Repo)
32:      Ecto.Adapters.SQL.Sandbox.mode(E2mapi.Repo, {:shared, self()})

3:Ecto.Adapters.SQL.Sandbox.mode(E2mapi.Repo, :manual)

I commented out the relevant sections and now mix test shows me green lights and my world is happy.

$ mix test
Compiling 3 files (.ex)

Finished in 0.03 seconds
3 tests, 0 failures

Randomized with seed 649726

Build Our Application

TODO… this is a work in progress… I will come back with a part 2, soon.