firestore cloud functions onCreate/onDelete sometimes immediately triggered twice

Question

I have observed this behavior occasionally with both onCreate and onDelete triggers.

Both the executions happened for the same document created in firestore. There

Answer 1

Based on @saranpol's answer we use the below for now. We have yet to check if we actually get any duplicate event ids though.

const alreadyTriggered = eventId => {
  // Firestore doesn't support forward slash in ids and the eventId often has it
  const validEventId = eventId.replace('/', '')

  const firestore = firebase.firestore()
  return firestore.runTransaction(async transaction => {
    const ref = firestore.doc(`eventIds/${validEventId}`)
    const doc = await transaction.get(ref)
    if (doc.exists) {
      console.error(`Already triggered function for event: ${validEventId}`)
      return true
    } else {
      transaction.set(ref, {})
      return false
    }
  })
}

// Usage
if (await alreadyTriggered(context.eventId)) {
  return
}