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Create webhooks

How to create webhooks in Optimizely Feature Experimentation.

To get the most value when using Optimizely Feature Experimentation, you will want changes made to your flag rules in the Optimizely UI to take effect in your applications as soon as possible.

One way to do this is to have your application poll for changes in the datafile that contains all the latest information on your experiments and flag deliveries. However, if you are using Optimizely in an application with a server-side component, Optimizely recommends configuring a webhook.

Optimizely Feature Experimentation sends a POST request to your supplied endpoint when you make a change in any environment.

When you change an environment, Optimizely Feature Experimentation updates the revision of only that environment's datafile. For example, if you have four environments and update one, Optimizely will only create a new datafile revision for that environment.

Using a webhook, Optimizely Feature Experimentation can notify your server when the datafile updates, eliminating the need to constantly poll and determine if there are changes in the Optimizely Feature Experimentation configuration. Once you receive the webhook and download the latest datafile, you must re-instantiate the Optimizely Feature Experimentation client with the latest datafile for the changes to take effect as soon as possible.

Use the following instructions to set up a webhook and test that it works correctly.

1. Set up an endpoint on your server

The first step to setting up a webhook is to set up a public API endpoint on your server, which can accept a POST request from Optimizely Feature Experimentation.

We recommend naming your endpoint /webhooks/optimizely. However, you can name the endpoint anything you would like.

Setting up a public endpoint on your server varies greatly depending on your language and framework. The examples below show Node (JavaScript) using Express and Python using Flask.

// Simple Node Express webhook example (see full example in step 3)
// Requires installing express: 'npm install --save express'
const express = require('express');
const app = express();

/**
 * Optimizely Webhook Route
 * Route to accept webhook notifications from Optimizely
 **/
app.post('/webhooks/optimizely', (req, res) => {
  console.log(`
    [Optimizely] Optimizely webhook request received!
    The Optimizely datafile has been updated. Re-download
    the datafile and re-instantiate the Optimizely SDK
    for the changes to take effect
  `);
  res.send('Webhook Received');
});

app.get('/', (req, res) => res.send('Optimizely Webhook Example'))

const HOST = process.env.HOST || '0.0.0.0';
const PORT = process.env.PORT || 8080;
app.listen(PORT, HOST);
console.log(`Example App Running on http://${HOST}:${PORT}`);
# Simple Python Flask webhook example (see full example in step 3)
# Requires installing flask: 'pip install flask'
import os
from flask import Flask, request, abort

app = Flask(__name__)

# Route to accept webhook notifications from Optimizely
@app.route('/webhooks/optimizely', methods=['POST'])
def index():
  print("""
    [Optimizely] Optimizely webhook request received!
    The Optimizely datafile has been updated. Re-download
    the datafile and re-instantiate the Optimizely SDK
    for the changes to take effect
  """)
  return 'Webhook Received'

@app.route('/')
def hello_world():
  return 'Optimizely Webhook Example'

if __name__ == "__main__":
  host = os.getenv('HOST', '0.0.0.0')
  port = int(os.getenv('PORT', 3000))
  print('Example App unning on http://' + str(port) + ':' + str(host))
  app.run(host=host, port=port)

2. Create a webhook in Optimizely Feature Experimentation

Once you have set up an endpoint on your server, take note of the fully qualified URL of the endpoint you created on your server. If your server domain is <https://www.your-example-site.com> and you named your endpoint /webhooks/optimizely as described in Step 1, then your fully qualified webhook URL is <https://www.your-example-site.com/webhooks/optimizely>. Use this URL in the steps below:

  1. Go to Settings > Webhooks.
  2. Click Create New Webhook...
  3. Enter the URL where Optimizely Feature Experimentation will send datafile update notifications (example: <https://www.your-example-site.com/webhooks/optimizely>)
  4. Click Save.
  5. Take note of the secret generated to secure your webhook in the next step.
create webhook

The example below shows the webhook payload structure with the default Optimizely primary environment of "Production"β€”your environment value may be different. Currently, we support one event type: project.datafile_updated. See Manage environments.

{
  "project_id": 1234,
  "timestamp": 1468447113,
  "event": "project.datafile_updated",
  "data": {
    "revision": 1,
    "origin_url": "https://optimizely.s3.amazonaws.com/json/1234.json",
    "cdn_url": "https://cdn.optimizely.com/json/1234.json",
    "environment": "Production"
  }
}

3. Secure your webhook

Once you have set up a public endpoint that can accept datafile update notifications, you will want to secure your webhook to ensure that these notifications are actually coming from Optimizely Feature Experimentation and not from some malicious user trying to control your server's feature flag configuration.

When you create a webhook, Optimizely Feature Experimentation generates a secret token that is used to create a hash signature of webhook payloads. Webhook requests include this signature in a header X-Hub-Signature that can be used to verify the request originated from Optimizely Feature Experimentation.

You can only view a webhook's secret token once, immediately after its creation. If you forget a webhook's secret token, you must regenerate it on the Settings > Webhook page.

πŸ“˜

Note

Be sure to keep all webhook secret tokens for your implementation secure and private.

The X-Hub-Signature header contains a SHA1 HMAC hexdigest of the webhook payload, using the webhook's secret token as the key and prefixed with sha1=. The way you verify this signature varies, depending on the language of your codebase. The reference implementation examples below show Node (JavaScript) using Express and Python using Flask.

Both examples assume your webhook secret is passed as an environment variable named OPTIMIZELY_WEBHOOK_SECRET.

// Simple Node Express webhook example (see full example in step 3)
// Requires installing express: 'npm install --save express body-parser'
const express = require('express');
const bodyParser = require('body-parser');
const crypto = require('crypto');
const app = express();

/**
 * Optimizely Webhook Route
 * Route to accept webhook notifications from Optimizely
 **/
app.post('/webhooks/optimizely', bodyParser.text({ type: '*/*' }), (req, res) => {
  const WEBHOOK_SECRET = process.env.OPTIMIZELY_WEBHOOK_SECRET;
  const webhookPayload = req.body;
  const hmac = crypto.createHmac('sha1', WEBHOOK_SECRET);
  const webhookDigest = hmac.update(webhookPayload).digest('hex');

  const computedSignature = Buffer.from(`sha1=${webhookDigest}`, 'utf-8');
  const requestSignature = Buffer.from(req.header('X-Hub-Signature', 'utf-8'));

  if (computedSignature.length != requestSignature.length || !crypto.timingSafeEqual(computedSignature, requestSignature)) {
    res.sendStatus(500);
    return;
  }

  console.log(`
    [Optimizely] Optimizely webhook request received!
    Signatures match! Webhook verified as coming from Optimizely
    Download Optimizely datafile and re-instantiate the SDK Client
    For the latest changes to take affect
  `);
  res.sendStatus(200);
});

app.get('/', (req, res) => res.send('Optimizely Webhook Example'));

const HOST = process.env.HOST || '0.0.0.0';
const PORT = process.env.PORT || 8080;
app.listen(PORT, HOST);
console.log(`Example App Running on http://${HOST}:${PORT}`);

# Reference Flask implementation of secure webhooks
# Requires installing flask: 'pip install flask'
# Assumes webhook's secret is stored in the environment variable OPTIMIZELY_WEBHOOK_SECRET
from hashlib import sha1
import hmac
import os

from flask import Flask, request, abort

app = Flask(__name__)

# Route to accept webhook notifications from Optimizely
@app.route('/webhooks/optimizely', methods=['POST'])
def index():
  request_signature = request.headers.get('X-Hub-Signature')
  webhook_secret = bytes(os.environ['OPTIMIZELY_WEBHOOK_SECRET'], 'utf-8')
  webhook_payload = request.data
  digest = hmac.new(webhook_secret, msg=webhook_payload, digestmod=sha1).hexdigest()
  computed_signature = 'sha1=' + str(digest)

  if not hmac.compare_digest(computed_signature, request_signature):
    print("[Optimizely] Signatures did not match! Do not trust webhook request")
    abort(500)
    return

  print("""
    [Optimizely] Optimizely webhook request received!
    Signatures match! Webhook verified as coming from Optimizely
    Download Optimizely datafile and re-instantiate the SDK Client
    For the latest changes to take affect
  """)
  return 'Secure Webhook Received'

@app.route('/')
def hello_world():
  return 'Optimizely Webhook Example'

if __name__ == "__main__":
  host = os.getenv('HOST', '0.0.0.0')
  port = int(os.getenv('PORT', 3000))
  print('Example App unning on http://' + str(port) + ':' + str(host))
  app.run(host=host, port=port)

❗️

Warning

To prevent timing analysis attacks, Optimizely strongly recommends that you use a constant time string comparison function such as Python's hmac.compare_digest instead of the == operator when verifying webhook signatures.

4. Test your implementation

To help ensure that your secure webhook implementation is correct, below are example values that you can use to test your implementation. These test values are also used in the running Node example in Runkit.

Example webhook secret token

yIRFMTpsBcAKKRjJPCIykNo6EkNxJn_nq01-_r3S8i4

Example webhook request payload

'{"timestamp": 1558138293, "project_id": 11387641093, "data": {"cdn_url": "https://cdn.optimizely.com/datafiles/QMVJcUKEJZFg8pQ2jhAybK.json", "environment": "Production", "origin_url": "https://optimizely.s3.amazonaws.com/datafiles/QMVJcUKEJZFg8pQ2jhAybK.json", "revision": 13}, "event": "project.datafile_updated"}'

Using the webhook secret token and the webhook payload as a string, your code should generate a compute signature of sha1=b2493723c6ea6973fbda41573222c8ecb1c82666, which can be verified against the webhook request header:

Example webhook request header

X-Hub-Signature: sha1=b2493723c6ea6973fbda41573222c8ecb1c82666
Content-Type: application/json
User-Agent: AppEngine-Google; (+http://code.google.com/appengine; appid: s~optimizely-hrd)

🚧

Important

Use a tool like Request Bin to test your webhooks. Request Bin lets you create a webhook URL to process HTTP requests and render the data in a human-readable format. Click Create a RequestBin on the Request Bin site and use the resulting URL as your endpoint URL for testing.