A event-driven framework for writing reliable and scalable system.

At a high level, it provides a few major components:

• Tools for core components with traits,
• Macros for processing events and commands

A Tour of Ruva

Ruva consists of a number of modules that provide a range of functionality essential for implementing messagebus-like applications in Rust. In this section, we will take a brief tour, summarizing the major APIs and their uses.

TCommand & Event

You can register any general struct with into_command Derive Macro as follows:

#[ruva::into_command]
pub struct MakeOrder {
    pub user_id: i64,
    pub items: Vec<String>,
}

As you attach into_command derive macro, MessageBus now is going to be able to understand how and where it should dispatch the command to.

Likewise, you can do the same thing for Event:

#[derive(Serialize, Deserialize, Clone, TEvent)]
#[internally_notifiable]
pub struct OrderFailed {
    pub user_id: i64,
}

#[derive(Serialize, Deserialize, Clone, TEvent)]
#[externally_notifiable(OrderAggregate)]
pub struct OrderSucceeded{
    #[identifier]
    pub id: i64,
    pub user_id: i64,
    pub items: Vec<String>
}

Notice that internally_notifiable event doesn't require aggregate specification while externally_notifiable event does along with its id with identifier attribute.

• internally_notifiable is marker to let the system know that the event should be handled within the application
• externally_notifiable event is stored as OutBox.

Initializing TCommandService

For messagebus to recognize service handler, TCommandService must be implemented, the response of which is sent directly to clients.

pub struct MessageBus {
event_handler: &'static TEventHandler<ApplicationResponse, ApplicationError>,
}
impl ruva::TMessageBus<ApplicationResponse,ApplicationError, Command> for MessageBus{
fn command_handler(
    &self,
    context_manager: ruva::AtomicContextManager,
    cmd: Command,
) -> impl ruva::TCommandService<ApplicationResponse, ApplicationError> {
    HighestLevelOfAspectThatImplementTCommandService::new(
        MidLevelAspectThatImplementTCommandService::new(
            TargetServiceThatImplementTCommandService::new(
                cmd, other_dependency
            )
        )
    )
}
}

For your convenience, Ruva provides declarative macros that handles transaction unit of work as you can use it as follows:

ruva::register_uow_services!(
	MessageBus,
	ServiceResponse,
	ServiceError,

	//Command => handler mapping
	CreateUserAccount => create_user_account,
	UpdatePassword => update_password,
    MakeOrder => make_order,
    DeliverProduct => deliver_product
)

Registering Event

Event is a side effect of command handling or yet another event processing. You can register as many handlers as possible as long as they all consume same type of Event as follows:

Example

use ruva::ruva_core::init_event_handler;

init_event_handler!(
{
    Response,
    Error,
    |ctx| YourServiceEventHandler::new(ctx),

    OrderFaild: [
           NotificationHandler::send_mail,
           ],
           
    #[asynchronous]
    OrderSucceeded: [
           DeliveryHandler::checkout_delivery_items,
           InventoryHandler::change_inventory_count
           ]
}
);

In the MakeOrder TCommand Handling, we have either OrderFailed or OrderSucceeded event with their own processing handlers. Events are raised in the handlers that are thrown to MessageBus by ContextManager. MessageBus then loops through the handlers UNLESS StopSentinel is received.

Handler API Example(Doc required)

MessageBus

At the core is event driven library is MessageBus, which gets command and gets raised event from UnitOfWork and dispatch the event to the right handlers. As this is done only in framework side, the only way you can 'feel' the presence of messagebus is when you invoke it. Everything else is done magically.

Example

#[ruva::into_command]
pub struct MakeOrder { // Test TCommand
    pub user_id: i64,
    pub items: Vec<String>
}

async fn test_func(){
    let bus = MessageBus::new(command_handler(), event_handler())
    let command = MakeOrder{user_id:1, items:vec!["shirts","jeans"]}
    match bus.execute_and_wait(command,Box::new(connection_pool())).await{
        Err(err)=> { // test for error case }
        Ok(val)=> { // test for happy case }
    }
    }
    }   
}

Error from MessageBus

When command has not yet been regitered, it returns an error - BaseError::NotFound Be mindful that bus does NOT return the result of event processing as in distributed event processing.