Fauna Event Feeds Now GA, Snapshot Export Available in Beta

Introducing Snapshot Export

Getting started with Event Feeds

import { Client, fql } from "fauna";

const client = new Client();

async function processFeed(client, query, startTs = null, sleepTime = 300) {

  let cursor = null;
  while (true) {
    // Only include `start_ts `if `cursor` is null. Otherwise, only include `cursor`.
    const options = cursor === null ? { start_ts: startTs } : { cursor: cursor };
    const feed = client.feed(query, options);

    for await (const page of feed) {
      for (const event of page.events) {
        switch (event.type) {
          case "add":
            console.log("Add event: ", event);
            break;
          case "update":
            console.log("Update event: ", event);
            break;
          case "remove":
            console.log("Remove event: ", event);
            break;
        }
      }
      // Store the cursor of the last page
      cursor = page.cursor;
    }

    // Clear startTs after the first request
    startTs = null;
    console.log(`Sleeping for ${sleepTime} seconds...`);
    await new Promise(resolve => setTimeout(resolve, sleepTime * 1000));
  }
}

const query = fql`Product.all().eventsOn(.price, .stock)`;
// Calculate timestamp for 10 minutes ago
const tenMinutesAgo = new Date(Date.now() - 10 * 60 * 1000);
const startTs = Math.floor(tenMinutesAgo.getTime() / 1000) * 1000000;

processFeed(client, query, startTs);

• Set a start_ts to begin fetching events from a specific point in time.
• Iterate over returned pages of events, performing logic for each event.
• Store the returned cursor to efficiently fetch subsequent events later on.

Hands-on example: Event Feeds sample app

import json
import time
from fauna import fql
from datetime import datetime, timedelta
from fauna.client import Client, FeedOptions

def lambda_handler(e, context):

  client = Client()

  # Get the previous feed cursor if it exists
  cursor = None
  options = None

  cursor_data = client.query(fql('Cursor.byName("ProductInventory").first()'))
  cursor = cursor_data.data.value if cursor_data.data.value else None

  # If no cursor exists, capture all events from previous 10 minutes
  if cursor is None:
    # Calculate timestamp for 10 minutes ago
    ten_minutes_ago = datetime.now() - timedelta(minutes=10)
    # Convert to microseconds
    start_ts = int(ten_minutes_ago.timestamp() * 1_000_000)

    options = FeedOptions(
      start_ts=start_ts
    )

  feed = client.feed(fql('Product.where(.stock < 25).eventSource()'), options)

  for page in feed:
    for event in page:
      event_type = event['type']
      if event_type == 'add':
        # Do something on add
        print('Add event: ', event)
      elif event_type == 'update':
        # Make an API call to another service on event
        # (i.e. email or slack notification)
        print('Update event: ', event)
      elif event_type == 'remove':
        # Do something on remove
        print('Remove event: ', event)

    # Store the cursor of the last page
    cursor = page.cursor
    # Store the cursor in the database
    cursor_update = client.query(fql('''
      Cursor.byName("ProductInventory").first()!.update({
        value: ${cursor}
      })
    ''', cursor=cursor))

    print(f'Cursor updated: {cursor}')

  return {
    "statusCode": 200,
    "body": json.dumps({
        "message": "Event feed processed successfully"
    })
  }

Get started today

1. Review the Event Feeds documentation for a deeper dive into capabilities and usage patterns.
2. Explore the Event Feeds sample app to learn how to integrate event feeds into a serverless architecture.
3. If you’re building with Cloudflare, the Fauna & Cloudflare serverless workshop incorporates Event Feeds along with additional robust Fauna functionality
4. Sign up for an account or contact us if you’re not on Pro or Enterprise yet, or want to discuss how event feeds fit into your specific use case.