CQRS/ES framework for building application in Rust
PostgresEventStore backend- Dispatch
CommandtoAggregateorCommandHandler - Generate
EventfromAggregateand persist them - Apply
EventtoAggregate - Store and notify
Eventwith subscriptions - Dispatch
EventtoEventHandler
Chekov works only with Postgres backend for now (and InMemory for test purpose). The choice is easy to make!
But some more backends need to be implemented, see the related issue.
An Aggregate is a struct that hold a domain state. Here's an example of a UserAggregate:
#[derive(Default, Aggregate)]
#[aggregate(identity = "user")]
struct User {
user_id: Option<Uuid>,
account_id: Option<Uuid>,
}
/// Define an Executor for the `CreateUser` command
/// The result is a list of events in case of success
impl CommandExecutor<CreateUser> for User {
fn execute(cmd: CreateUser, _state: &Self) -> Result<Vec<UserCreated>, CommandExecutorError> {
Ok(vec![UserCreated {
user_id: cmd.user_id,
account_id: cmd.account_id,
}])
}
}
/// Define an Applier for the `UserCreated` event
/// Applier is a mutation action on the aggregate
#[chekov::applier]
impl EventApplier<UserCreated> for User {
fn apply(&mut self, event: &UserCreated) -> Result<(), ApplyError> {
self.user_id = Some(event.user_id);
self.account_id = Some(event.account_id);
Ok(())
}
}You need to create a struct per command, any type of struct can implement Command but we advise to use struct for a better readability.
A command can only produce (or not) one type of events and it targets a single Aggregate.
A command must have a single and unique identifier that is used to route the command to the right target.
#[derive(Debug, Command)]
#[command(event = "UserCreated", aggregate = "User")]
struct CreateUser {
#[command(identifier)]
user_id: Uuid,
account_id: Uuid,
}An Event can be a struct or an enum.
#[derive(Event, Deserialize, Serialize)]
struct UserCreated {
user_id: Uuid,
account_id: Uuid,
}Not implemented yet
No its not. Some critical part of the project are still not implemented and a lot of code needs to be refactored before that.
Feel free to open issue in case of bugs or features requests. Discussions are also a great starts if you have issue that are not bugs nor features requests.
The project is really early staged and have a lot of pending tasks, one major tasks is to produce a roadmap or some issues that can be used to expose the project vision. Feel free to open a Discussions around it if you want !