Unprepared live-coding session to explain concepts during the course.
For those interested in a job or intern position, please contact me through :
[email protected] or add my associate linkedIn (he is aware of the IMT class
and your interest) : https://www.linkedin.com/in/jerome-benoliel-6b260316/. No
need to be hesitant Jerome can explain you the company, and our big and
interesting projects for large industry and retail groups.
Please :
- first install elixir to really test the files : http://elixir-lang.github.io/install.html.
- Then read the course slides : slides in this repo
- Then clone this repo to test :
git clone https://github.com/awetzel/imt_actor_course_2017 - Then read this README and each part
course_part_x.exsfiles - Then and only then (actor principles are more important than the given language) read the Elixir language documentation http://elixir-lang.github.io/getting-started
- If you want to read the same in the erlang language : read http://learnyousomeerlang.com/content
The use case is to manage a bank account
- with an initial credit hold of
4€ - then credit 5€
- then credit 2€
- then debit 3€
- then show current credit hold : should be 8€
This course try to "show" the principles of the actor model, how it is applied in practice in a functional language (Erlang/Elixir). The idea is to build the "account application" incrementally :
- part0: from scratch first : with only a raw functional language
- part1: then with a micro-process/coroutine system sending message
- part2: then splitting the generic server logic from the business account logic
- part3: then with the Erlang/Elixir libraries to create the coroutine
- part4: then with a supervisor to handle error and restart the coroutine
- part5: then with the Erlang/Elixir libraries to create the supervisor
- part6: then with the Erlang-OTP/Elixir-tooling way to create the concept of "application"
elixir course_part_0.exs
standard functionnal programming : the function transform immutable data : stateless.
Problem : is you want the system to manage the bank account state,
and not let an external stateful system (database, filesystem) to
manage it... You need your software to be a permanent server with
account in the server RAM : see course_part_1
elixir course_part_1.exs
Use spawn_link, receive and send (core low level functions of erlang)
to create the account server.
elixir course_part_2.exs
Create 2 different modules :
- one to handle a generic server.
- one other to handle the way you want the server to behave
Put the second module (behaviour module) in the generic server state.
elixir course_part_3.exs
Show that a complete and featurefull generic server is in the standard Library : GenServer : to build server nodes in a supervision tree. Show that it behaves exactly the same as the custom generic server developed in part 2.
elixir course_part_4.exs
Develop a special simple type of server, which role is to start child
servers, and restart them when they fail.
Introduce a bug to make credit 2 fail, then show that the code is
still "working" - but the account server came back to it's initial working state.
elixir course_part_5.exs
Show that a complete and featurefull supervisor server is in the standard Library : Supervisor : to build supervisor nodes in a supervision tree. Show that it behaves pretty much the same as the custom simple supervisor developed in part 4.
cd course_part_6
mix test
Erlang OTP applications includes : a configuration system, a standard way to layout your code, a standard way to start a named "root supervisor". Elixir gives you a way to build these applications with nice tooling :
- config/config.exs manamement
- mix.exs to describe application
- test/*_test.exs files for unit testing
mix test launches the application then unit tests where the test cases has
been put.
iex -S mix launches the application then give you an elixir shell connected
to this application. You can try to call GenServer.call(:account_server,:get)
in this shell to communicate "in live" with the account server.