Delivering High Quality Elixir Code using Gitlab

Penyajian
Delivering High Quality Elixir
Code into Your Production
Line
Oleh
Tonny Adhi Sabastian
Jakarta, 2020
tonny.adhi@ui.ac.id / tonny.adhi@ruma.co.id | http://kambing.ui.ac.id

● 13 years of experiences at IT Industry and Academy
● Former chief of Network Administrator at Universitas
Indonesia and volunteer System Administrator for
kambing.ui.ac.id F/OSS repository
● Former (part time) lecturer and researcher at Faculty of
Computer Science Universitas Indonesia and also
Universitas Gunadarma
● Currently work at MAPAN ( Gojek Group ) as Tech. Architect
and Senior Engineer
● Topics of interest:
○ Linux Kernel, especially in Networking Stack, Kernel
Performance and Network Security
○ Distributed System in general - including Cloud
Computing
○ System Performance and Optimization
○ Pervasive Computing and Internet of Things
Tonny Adhi Sabastian
Sekilas

Agenda
MAPAN 101
Quick Bootstrapping on Elixir
Quality Assurance on Elixir Code
Elixir Pipeline on Gitlab

(1) MAPAN 101
source https://mapan.id
license limited use, only for MAPAN Publication
Gb. Tangkapan Layar

Kami percaya bahwa semua orang berhak untuk mengakses
layanan yang membantu mereka mencapai hidup mapan
- Bagian dari Ikrar Mapan

A Short History of MAPAN
● Founded in 2009 as PT Ruma by Aldi Haryopratomo
○ Selling Airtime
● Adding Bill Payment Product in 2012
● Branchless Banking Pilot with Bank of Indonesia in 2013
● Started serving physical goods to member in 2014
● Launching Arisan Mapan in 2015
● Member of Gojek Group since 2017
● Selling Digital Product from Gojek since 2019
● New Mapan App is launched on March 2020
○ Enabling various services on the platform

Arisan MAPAN
● We sell Household Goods
○ Cooking Pans
○ Furnitures
● Enabling community engagement in the spirit of
“Gotong Royong”
● Members will pay through “Arisan” Installments
○ More here:
https://www.mapan.id/apa-itu-arisan-mapan/arisan-
barang/

MAPAN Tech Stack
source various respective sources
license Apache License 2.0, Fair Use, and Public Domain

(2) Bootstrapping Elixir
license CC-BY-SA, Fair Use
fn ( , ) ->

Elixir is Awesome
source self()
license CC-BY-SA

Interactive Elixir (1.10.2) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> defmodule Collection do
...(1)> def add_element_to_collection(collection, element) do
...(1)> collection ++ [element]
...(1)> end
...(1)> end
iex(2)> collection = [1,2,3,4]
[1, 2, 3, 4]
iex(3)> Collection.add_element_to_collection(collection, 5)
[1, 2, 3, 4, 5]
iex(4)> IO.inspect collection
[1, 2, 3, 4]
Immutable
# Elixir Shell

iex(7)> handle_result = fn
...(7)> {:ok, result} -> IO.puts "Handling result..."
...(7)> {:ok} -> IO.puts "Single Item"
...(7)> {:error} -> IO.puts "An error has occurred!"
...(7)> end
iex(8)> some_result = 2
2
iex(9)> handle_result.({:ok, some_result})
Handling result...
:ok
iex(10)> handle_result.({:ok})
Single Item
:ok
Pattern Matching
# Elixir Shell

iex(14)> 1..1_000_000
...(14)> |> Enum.map(&(Task.async(fn -> &1 * &1 end)))
...(14)> |> Enum.map(&Task.await/1)
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225, 256, 289, 324,
361, 400, 441, 484, 529, 576, 625, 676, 729, 784, 841, 900, 961, 1024, 1089,
1156, 1225, 1296, 1369, 1444, 1521, 1600, 1681, 1764, 1849, 1936, 2025, 2116,
2209, 2304, 2401, 2500, ...]
Processes (1)
# Elixir Shell

$ iex --sname bejo@localhost
Erlang/OTP 22 [erts-10.6.4] [source] [64-bit] [smp:8:8] [ds:8:8:10]
[async-threads:1] [hipe]
iex(bejo@localhost)1> defmodule Bejo do
...(bejo@localhost)1> def say_name do
...(bejo@localhost)1> IO.puts "Halo, Nama gue bejo."
...(bejo@localhost)1> end
...(bejo@localhost)1> end
$iex --sname surti@localhost
Erlang/OTP 22 [erts-10.6.4] [source] [64-bit] [smp:8:8] [ds:8:8:10]
[async-threads:1] [hipe]
iex(surti@localhost)1> Node.spawn_link(:bejo@localhost, fn -> Bejo.say_name end)
Halo, Nama gue bejo.
#PID<10888.124.0>
Processes (2)
# Elixir Shell

(3) Quality Assurance
on Elixir Code
license CC-BY-SA
-> ->

Code Review by Peers ( senior
engineer, tech lead / head,
architect ).
1) Code Review
Run unit test on pipeline. Block
if it bellow coverage
2) Unit
Testing Run credo linter of pipeline.
Block if linter state that part
of code need more review
3) Code Lint
Typespec, Unreachable Code,
Pattern that never match. Block if
discrepancy found
4) Discrepancy
Check
Check if any dependencies
for a project contain CVE.
Block if a CVE found
5) CVE
Checking
Elixir Pipeline with Quality as
Concern

Same with previous step. The
different is only we do CVE
check on Docker Image that
use for a project deployment
6)Docker
Image CVE
Checking
Elixir Pipeline with Quality as
Concern
Functional Test done by QA
ofﬁcer. It can be automated and
embedded within pipeline
7)Functional
Testing

Code Linting using
Credo (1)
https://github.com/rrrene/credo

Code Linting using
Credo (2)
# Bash Shell
# add credo in your project
$ vi mix.exs
…
defp deps do
[
{:credo, "~> 1.3", only: [:dev, :test], runtime: false}
]
end
…

Code Linting using
Credo (3)

Discrepancy Check
using Dialyxir (1)
https://github.com/jeremyjh/dialyxir

# Bash Shell
# add dialyxir in your project
$ vi mix.exs
…
def project do
[
dialyzer: [
plt_add_deps: :transitive,
plt_add_apps: [:mix, :ex_unit],
check_plt: true,
ignore_warnings: "dialyzer.ignore-warnings"
]
end
…
defp deps do
[
{:dialyxir, "~> 1.0", only: [:dev, :test], runtime: false}
]
end
…
Discrepancy Check
using Dialyxir (2)
https://github.com/jeremyjh/dialyxir

Unit Test Coverage
using Excoveralls (1)
https://github.com/parroty/excoveralls

# Bash Shell
# coveralls.json
$ cat coveralls.json
…
{
"coverage_options": {
"minimum_coverage": 90
},
"skip_files": [
"lib/phxchat_web.ex"
]
}
…
Unit Test Coverage

# Bash Shell
# add excoverallw into your project
$ vi mix.exs
…
def project do
[
…
test_coverage: [tool: ExCoveralls],
preferred_cli_env: [
coveralls: :test,
"coveralls.detail": :test,
"coveralls.post": :test,
"coveralls.html": :test
],
…
]
end
…
defp deps do
[
{:excoveralls, "~> 0.12", only: [:dev, :test]}
]
end
…
Unit Test Coverage

Showcase
( https://gitlab.mapan.io/tonny.adhi/phxchat/ )

Reference List for Elixir Study
Sites :
○ https://elixircasts.io/
○ https://elixirschool.com/en/
○ https://alchemist.camp/
○ https://elixirweekly.net/
○ https://elixirstatus.com/
○ https://www.nerves-project.org/
Books :
○ Learn Functional Programming with Elixir, by Ulises
Amelia
○ Functional Web Development with Elixir, OTP, and
Phoenix, by Lance Halvorsen
○ Elixir in Action Second Edition, by Sasa Juric

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