Correlation id

An identifier that can be used to relate or correlate messages together. This value is sticky meaning that when a message is received with a correlation id, any messages that are sent as a result will contain the same correlation id.

Correlation ids are a useful mechanism for logging and tracking message flows through the system. They're also the default mechanism to correlate messages orchestrated by workflows to continue the next step in a process.

const start = () => {
  const bus = await Bus.configure()
    .withHandler(
      ChargeCreditCard,
      async () => await bus.publish(new CreditCardCharged())
    )
    .initialize()
  await bus.start()
  
  await bus.send(
    new ChargeCreditCard(),
    { correlationId: 'cd091b26-f0e6-43fb-9962-c06786948e26' }
  )
}

In this example, a ChargeCreditCard command is being sent with a correlation id ('cd091b26-f0e6-43fb-9962-c06786948e26').

This will be handled and an event called CreditCardCharged published as a result. This event will have a correlation id of the same value.