Packages

•  package root

  Definition Classes

  root

•  package csw

  Definition Classes

  root

•  package event

  Definition Classes

  csw

•  package client

  This module implements an Event Service responsible for publishing an csw.params.events.Event or subscribing to an csw.params.events.Event.

  Event Service

  This module implements an Event Service responsible for publishing an csw.params.events.Event or subscribing to an csw.params.events.Event. An event is published on a csw.params.events.EventKey. The event key is composed of a csw.prefix.models.Prefix depicting the source and an csw.params.events.EventName. The subscriber can subscribe to the csw.params.events.EventKey to receive all events published on the Key.

  Example: Event Service

  val eventServiceFactory          = new EventServiceFactory()
  val eventService: EventService   = eventServiceFactory.make(locationService)

  Using above code, you can create instance of csw.event.api.scaladsl.EventService. EventService is the factory to create publishers and subscribers.

  You can choose to use defaultPublisher in case you want to share same connection for publishing different events.

  Example: Event Publisher

  Event Publisher provides asynchronous APIs to publish one or more Events

  val event = SystemEvent(prefix, EventName("filter_wheel"))
  
  val publisher    = eventService.defaultPublisher
  publisher.publish(event)

  Example: Event Subscriber (subscribe and get API)

  Event Subscriber provides asynchronous APIs to subscribe to one or more Event Keys. It also provides APIs to subscribe using a pattern. In addition, there are APIs to get latest events for one ore more Event Keys without making a subscription

  The EventSubscriber provides various API's to subscribe to csw.params.events.EventKey. One of such a subscribe method takes an ActorRef of an arbitrary actor or a callback function to be called when an event matching the given csw.params.events.EventKey is received. In the example below, we only provide the callback argument value. You could also provide an ActorRef of some actor that should receive the Event message.

   def callback(ev: Event): Unit = {
     // ...
   }
  
   async {
     val subscriber    = eventService.defaultSubscriber
     subscriber.subscribeCallback(Set(EventKey(prefix, EventName("filter_wheel"))), callback)
  
     val event = await(subscriber.get(event.eventKey))
  
     event match {
       case e: ObserveEvent => assert(e.prefix == expectedPrefix)
       case _               => fail("Expected ObserveEvent")
     }
  }

  csw provides two implementations for Event Service which can be accessed through csw-event-client : 1. RedisEventService - Redis as event store and publisher/subscriber functionality 2. KafkaEventService - Kafka as event store and publisher/subscriber functionality

  Complete guide of usage of different API's provided by EventService is available at: https://tmtsoftware.github.io/csw/services/event.html

  Definition Classes

  event

•  package models

  Definition Classes

  client

•  object EventStores

  Event service supports two underlying implementations for event store 1.

  Event service supports two underlying implementations for event store 1. csw.event.client.models.EventStores.RedisStore: This is the default and recommended store. If you are creating csw.event.api.scaladsl.EventService using csw.event.client.EventServiceFactory, then you should shutdown redis client when it is no longer in use. 2. csw.event.client.models.EventStores.KafkaStore: This can be used to create an csw.event.api.scaladsl.EventService which is backed by Kafka event store. You should not use this unless you have strong reasons to do so.

  Definition Classes

  models

  Note

  If you are using csw-framework, your component will already have an event service injected which is backed up by csw.event.client.models.EventStores.RedisStore. You do not need to take the csw.event.client.EventServiceFactory route.

• KafkaStore
• RedisStore

csw.event.client.models.EventStores

KafkaStore