Adopting Elixir

Message Delivery Guarantees

Good developers often associate certain words with particular pitfalls or techniques for avoiding them. Large dataset aggregation suggests the map-reduce pattern; immutability may suggest functional languages. In this section, we’ll build another association. Whenever you consider events, you should also consider message delivery guarantees.

Consider a simple welcome email that you might want to send each time a user creates an account. You could do so asynchronously with the Task module, but if the client fails or the server abruptly terminates, the email won’t be sent. Maybe you are willing to live with the consequences—if the email contained the user confirmation token, they can always request a new one later. ...