As discussed in my last Elixir Tutorial post we are trying to build a redis driven page fetcher that will:

connect to redis
pop a tuple of information that identifies what to fetch including a url
will fetch the page from the internet
will save the html to a database table for processing

Given that Elixir is new to me (and arguably most people), the question of how to get this running on a server is actually a big deal. Getting stuff running on a server is what is called deployment and deploying code can be tricky. It literally took years before I was comfortable with the state of Ruby deployment and it is only relatively recently that I would posit that Capistrano is actually good. So given the relatively embryonic state of Elixir, what are our deployment options:

git clone to a server and adjust settings manually as needed
build to a container and push
use a CI tool like this approach
e-deliver
distillery

For this tutorial, I'm going to do a straight git clone to make sure I understand how an Elixir app is structured and then I'll likely move to either distillery or e-deliver in a later tutorial.

Getting Elixir Installed Server Side

I'm working on an Ubuntu 14.04 trusty box for this. Here are the steps from elixir-lang:

wget https://packages.erlang-solutions.com/erlang-solutions_1.0_all.deb && sudo dpkg -i erlang-solutions_1.0_all.deb
sudo apt-get update
sudo apt-get install esl-erlang
sudo apt-get install elixir

If you have at all an unreliable network connection then run Tmux first so connection loss doesn't bork your install.

Please note that while your results may vary, this is not a fast install by any means. I witnessed the erlang install take more than 40 minutes or enough time to browse the internet quite a bit, discover timezone.io and setup a whole remote organization with it. Very cool.

Cloning Your Project

As long as your server has access to Github then it should be a simple matter of:

mkdir ~/elixir (to give a project root)
cd ~/elixir
git clone git@github.com:fuzzygroup/elixir_page_fetcher.git

Then to test your project:

cd ~/elixir/elixir_page_fetcher
mix deps.get
answer Y to install the hex package manager or do mix local.hex –force as your first step
mix test

If all goes well the code should compile and the test should run. Here's what the whole process looked like for me:

[foo@adl-ad-work2 /home/foo/srv/current]$ cd ~/elixir/elixir_page_fetcher/
[foo@adl-ad-work2 /home/foo/elixir/elixir_page_fetcher]$ mix deps.get
Could not find Hex, which is needed to build dependency :exredis
Shall I install Hex? (if running non-interactively, use: "mix local.hex --force") [Yn] Y
* creating /home/foo/.mix/archives/hex-0.13.0
Running dependency resolution
* Getting exredis (Hex package)
  Checking package (https://repo.hex.pm/tarballs/exredis-0.2.5.tar)
  Fetched package
* Getting eredis (Hex package)
  Checking package (https://repo.hex.pm/tarballs/eredis-1.0.8.tar)
  Fetched package
[foo@adl-ad-work2 /home/foo/elixir/elixir_page_fetcher]$ mix test
Could not find "rebar", which is needed to build dependency :eredis
I can install a local copy which is just used by Mix
Shall I install rebar? (if running non-interactively, use: "mix local.rebar --force") [Yn] Y
* creating /home/foo/.mix/rebar
* creating /home/foo/.mix/rebar3
==> eredis (compile)
Compiled src/basho_bench_driver_erldis.erl
Compiled src/eredis.erl
Compiled src/eredis_sub.erl
Compiled src/basho_bench_driver_eredis.erl
Compiled src/eredis_sub_client.erl
Compiled src/eredis_client.erl
Compiled src/eredis_parser.erl
==> exredis
Compiling 5 files (.ex)
Generated exredis app
==> page_fetcher
Compiling 1 file (.ex)
Generated page_fetcher app
.

Finished in 0.1 seconds
1 test, 0 failures

Randomized with seed 243121

Understanding Some Elixir Ecosystem Basics

There were a number of things in the output above that may need some clarification:

Erlang - this is the root language which Elixir is written in. Erlang provides a language, a virtual machine and the OTP framework which is designed for building concurrent, distributed applications.
Hex - this is the underlying package manager for Elixir. Think of it as Ruby Gems but improved.
Rebar - this is a build tool which makes it easier to build Erlang applications

Next Time

In the next tutorial I will, hopefully, actually get to write some working Elixir code - what I've been trying to work towards for weeks if not months.