EventBus.Model.Event Data Structure

Attributes

%EventBus.Model.Event{} struct type consist of 8 attributes including 3 attributes (id, topic and data) as mandatory and 5 attributes (transaction_id, initialized_at, occurred_at, ttl and source) as optional.

Mandatory Attributes

id

Identifier for the Event struct type, it must be unique in all over the system. It can be a type of String.t() or integer(). A good way to generate it is to use a unique identifier generator like UUID.uuid4() function.

topic

The topic name for the Event struct type. It can be a type of atom(). As the best practice of event-driven development, it is a good convention to set the topic name as past tense of actions like :user_created, :email_sent, or webhook_received.

data

The event data, it can be any() type. It might be considered as an aggregated content of an event. For example, if you created a user, then the User struct might be a good candidate for the data attribute.

---

Optional Attributes

initialized_at

Optional, but good to have the field for all events to track when the event generator started to process for generating this event. It can be a type of integer().

occurred_at

Optional, but good to have the field for all events to track when the event occurred with unixtimestamp value. The library does not automatically set this value since the value depends on the timing choice. It can be a type of integer().

source

Source attribute is used to determine the source of the Event. It usually answers the question who created this event.

transaction_id

The transaction identifier attribute is an optional field for the struct. It can be a type of String.t() or integer(). If you need to store any meta-identifier related to event transaction, it is the place to store. Secondly, transaction_id is one of the good ways to track events related to the same transaction on a chain of events. If you have time, have a look at the story.

ttl

Optional, but might have the field for all events to invalidate an event after a certain amount of time. Currently, the event_bus library does not do any specific thing using this field. If you need to discard an event in a certain amount of time, that field would be very useful. It can be a type of integer().

Note: If you set the ttl field, then occurred_at field also becomes a required field.