Programmer Passport: OTP

OTP Supervisors Manage GenServer Lifecycles

Let’s create a new project, one with a supervisor. We’ll call this app super_duper:

[otp] ➔ mix new super_duper --sup
...
* creating lib/super_duper/application.ex
...

[otp] ➔ cd super_duper/

Notice the list of files mix created for you. One of them is application.ex. That’s your supervisor.

Application is a Supervisor Template

Just as the GenServer module is a template for a generic server, the Application module is a template for a supervisor. The documentation says, “Applications are the idiomatic way to package software in Erlang/OTP.” When you start an application, you’re really starting a supervisor, and that supervisor is starting the GenServers that make up the rest of your code base. ...