Maestro

v0.0.1

Maestro v0.0.1 Maestro.Aggregate behaviour View Source

Traditional domain entities are referred to as aggregates in the literature. The goal of this library is to greatly simplify the process of implementing a event sourcing application by owning the flow of non-domain data (i.e. commands, events, and snapshots) to allow you to focus on the business logic of evaluating commands and applying events to your domain objects.

The most crucial piece to this is the aggregate. It defines a behaviour wherein the developer must implement the callbacks for eval_command and apply_event. This allows the library to work through the lifecycle of a command and its events in a controlled, consistent manner.

The aggregate behaviour provides the following utilities for managing state:

  • ID and sequence tracking (to reduce duplication of effort)
  • all necessary GenServer hooks (i.e. handle_call, start_link,init)
  • updating state via snapshots and events

Link to this section Summary

Types

agg()
t()

Functions

child_spec(opts)
start_link(opts)

Callbacks

apply_event(agg, event)
eval_command(agg, command)
initial_state()
prepare_snapshot(agg)
use_snapshot(agg, snapshot)

Link to this section Types

Link to this type t() View Source 
t() :: %Maestro.Aggregate{
  id: HLClock.Timestamp.t(),
  sequence: integer(),
  state: any()
}

Link to this section Functions

Link to this section Callbacks

Link to this callback apply_event(agg, event) View Source 
apply_event(agg(), event :: Maestro.Schemas.Event.t()) :: any()
Link to this callback eval_command(agg, command) View Source 
eval_command(agg(), command :: Maestro.Command.t()) :: [
  Maestro.Schemas.Event.t()
]
Link to this callback initial_state() View Source (optional) 
initial_state() :: any()
Link to this callback prepare_snapshot(agg) View Source (optional) 
prepare_snapshot(agg()) :: map()
Link to this callback use_snapshot(agg, snapshot) View Source (optional) 
use_snapshot(agg(), snapshot :: Maestro.Schemas.Snapshot.t()) :: any()