The GenServer Pattern

Parts of a GenServer

There’s a simple pattern at the heart of every bit of functionality we build in a GenServer. It has three moving parts:

• A client function
• A function from the GenServer module
• A callback

The client function is the public interface, the part that other processes will call. Within the client function, we call a GenServer module function that does some internal work before it triggers a callback. The callback is where we do the real work and return a response. Here is the pattern of the GenServer module: