PubSub

First, declare a new topic:

package payments

type Invoices = ftl.TopicHandle[Invoice, ftl.SinglePartitionMap[Invoice]]

Note that the name of the topic as represented in the FTL schema is the lower camel case version of the type name.

The Invoices type is a handle to the topic. It is a generic type that takes two arguments: the event type and the partition map type. The partition map type is used to map events to partitions. In this case, we are using a single partition map, which means that all events are sent to the same partition.

Then define a Sink to consume from the topic:

//ftl:subscribe payments.invoices from=beginning
func SendInvoiceEmail(ctx context.Context, in Invoice) error {
  // ...
}

Events can be published to a topic by injecting the topic type into a verb:

func PublishInvoice(ctx context.Context, topic Invoices) error {
   topic.Publish(ctx, Invoice{...})
   // ...
}

First, declare a new topic :

@Export
@Topic("invoices")
internal interface InvoiceTopic : WriteableTopic<Invoice>

Events can be published to a topic by injecting it into an @Verb method:

@Verb
fun publishInvoice(request: InvoiceRequest, topic: InvoiceTopic) {
    topic.publish(Invoice(request.getInvoiceNo()))
}

To subscribe to a topic use the @Subscription annotation, referencing the topic class and providing a method to consume the event:

@Subscription(topic = InvoiceTopic::class, from = FromOffset.LATEST)
fun consumeInvoice(event: Invoice) {
    // ...
}

If you are subscribing to a topic from another module, FTL will generate a topic class for you so you can subscribe to it. This generated topic cannot be published to, only subscribed to:

@Topic(name="invoices", module="publisher")
internal interface InvoiceTopic : ConsumableTopic<Invoice>

First, declare a new topic:

@Export
@Topic("invoices")
interface InvoiceTopic extends WriteableTopic<Invoice> {}

Events can be published to a topic by injecting it into an @Verb method:

@Verb
void publishInvoice(InvoiceRequest request, InvoiceTopic topic) throws Exception {
    topic.publish(new Invoice(request.getInvoiceNo()));
}

To subscribe to a topic use the @Subscription annotation, referencing the topic class and providing a method to consume the event:

@Subscription(topic = InvoiceTopic.class, from = FromOffset.LATEST)
public void consumeInvoice(Invoice event) {
    // ...
}

If you are subscribing to a topic from another module, FTL will generate a topic class for you so you can subscribe to it. This generated topic cannot be published to, only subscribed to:

@Topic(name="invoices", module="publisher")
 interface InvoiceTopic extends ConsumableTopic<Invoice> {}