Subscriptions

There are 3 different subscription types.
Simple stream subscriptions, persistent subscriptions and catchUp subscriptions.

Subscribe to stream

You can use subscribe() at stream instances and simply adding listener(s) to returned subscription.
There are two options.

Listen to all events:

const eventstore = new Eventstore()
await eventstore.connect()

subscription = await eventstore
      .stream('streamId')
      .subscribe()

subscription.on('event', (event) => {
  console.log(event.name)
})

Listen for specific event:

const eventstore = new Eventstore()
await eventstore.connect()

subscription = await eventstore
      .stream('streamId')
      .subscribe()

// listen for "event-"+ lowercase event name
subscription.on('event-specificeventa', (event) => {
  console.log('log only SpecificEventA')
})

With this approach you're able to add different listeners for different needs to one single stream subscription.

Persistent subscription

You can create persistent subscriptions (needs admin rights)

const eventstore = new Eventstore()
await eventstore.connect()

const persistentSubscription = await eventstore
  .atStream('myStream')
  .withCredentials({username: 'admin', password: 'changeit'})
  .createPersistentSubscription('persistentsubscription')

You can update an existing persistent subscription (needs admin rights)

const eventstore = new Eventstore()
await eventstore.connect()

const newConfig = {
    messageTimeoutMilliseconds : 30000
  }

const persistentSubscription = await eventstore
  .atStream('myStream')
  .withCredentials({username: 'admin', password: 'changeit'})
  .getPersistentSubscription('persistentsubscription')
  .update(newConfig)

You can delete an existing persistent subscription (needs admin rights)

const eventstore = new Eventstore()
await eventstore.connect()

const newConfig = {
    messageTimeoutMilliseconds : 30000
  }

const persistentSubscription = eventstore
  .atStream('myStream')
  .withCredentials({username: 'admin', password: 'changeit'})
  .getPersistentSubscription('persistentsubscription')

await persistentSubscription.delete()

You can connect to an existing persistent subscription

const eventstore = new Eventstore()
await eventstore.connect()

const newConfig = {
    messageTimeoutMilliseconds : 30000
  }

const persistentSubscription = eventstore
  .atStream('myStream')
  .getPersistentSubscription('persistentsubscription')

await persistentSubscription.subscribe()

Unsubscribing an existing persistent subscription is also pretty easy

await persistentSubscription.unsubscribe()

CatchUp subscriptions

/** TODO **/
not implemented yet

Emitted events

• subscribed emitted after subscription is established
• dropped emitted when subscription is dropped
• event emitted when event appeared (param: Event)
• event-eventnametolowercase emitted when event appeared (param: Event)
• error emitted in error case (param: Error)