# `@pebula/attribus`

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**AttriBus** (Attribute Driven ServiceBus) is a library that provide the tools to create an attribute driven service bus architecture.
It simplifies how we use and manage service bus through an declarative API that automate message handling & emitter registration:

:::info
**AttriBus** is a wrapper around the [Azure Service Bus JS client library](https://github.com/Azure/azure-sdk-for-js/tree/master/sdk/servicebus/service-bus)
:::

### Message Handling

Handling incoming service bus message is now as easy as handling incoming REST requests.

```typescript
export class ServiceBusController {
  @Queue<MethodDecorator>(({
    name: 'attribus-queue.demo'
  })
  async myQueueEntity(context: SbContext) {
  }
}
```

### Client Emitters

Defining service bus emitters (`Sender`) requires no logic, you can compose a client emitter in seconds:

```typescript
export class ServiceBusEmitClient {

  @QueueEmitter({
    name: 'attribus-queue.demo'
  })
  myQueueEntity: Sender;
}
```

### Easy Setup

The library also helps with service bus entity management through a declarative API for automatic creation
of service bus entities based on the entities we define in the controllers / services in our application.

We call it **provision**.

This allows a **code-first** approach for service bus management and architecture.

### Leverage Advanced Architecture Patterns

By simplifying the work with service bus, **AttriBus** enables the use of more advanced architecture patterns that you
can use to manage the flow of your application.

Using **Observables** you can now implement a **CQRS** or **Event Sourcing** models out of the box.
In addition, **Observables** along with **Interceptors** allow us to use plugins that encapsulate behaviors for us.

For example, the **SbBackoffRetry plugin** wraps incoming service bus messages and handles them when their handler throws.
It will perform a retry to handle them again but with a delay between each try. The delay is not constant and it is based on an algorithm (linear / exponential)
so the effect of periodic stress on you server is reduced.