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Heroku Webhooks

TL;DR

To integrate Heroku webhooks with ngrok:

  1. Launch your local webhook. npm start
  2. Launch ngrok. ngrok http 3000
  3. Configure Heroku webhooks with your ngrok URL.
  4. Secure your webhook requests with verification.

This guide covers how to use ngrok to integrate your localhost app with Heroku by using Webhooks. Heroku webhooks can be used to notify an external application whenever specific events occur in your Heroku account.

By integrating ngrok with Heroku, you can:

  • Develop and test Heroku webhooks locally, eliminating the time in deploying your development code to a public environment and setting it up in HTTPS.
  • Inspect and troubleshoot requests from Heroku in real-time via the inspection UI and API.
  • Modify and Replay Heroku Webhook requests with a single click and without spending time reproducing events manually in your Heroku account.
  • Secure your app with Heroku validation provided by ngrok. Invalid requests are blocked by ngrok before reaching your app.

Step 1: Start your app​

For this tutorial, we'll use the sample NodeJS app available on GitHub.

To install this sample, run the following commands in a terminal:

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This will get the project installed locally.

Now you can launch the app by running the following command:

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The app runs by default on port 3000.

You can validate that the app is up and running by visiting http://localhost:3000. The application logs request headers and body in the terminal and responds with a message in the browser.

Step 2: Launch ngrok​

Once your app is running successfully on localhost, let's get it on the internet securely using ngrok!

  1. If you're not an ngrok user yet, just sign up for ngrok for free.

  2. Download the ngrok agent.

  3. Go to the ngrok dashboard and copy your Authtoken.
    Tip: The ngrok agent uses the auth token to log into your account when you start a tunnel.

  4. Start ngrok by running the following command:

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  5. ngrok will display a URL where your localhost application is exposed to the internet (copy this URL for use with Heroku). ngrok agent running

Step 3: Integrate Heroku​

To register a webhook on your Heroku account follow the instructions below:

  1. Access Heroku and sign in using your Heroku account.

  2. On the Dashboard page, click the name of a app from the Personal app list. Tip: If you don't have an app, create a new one by clicking New and then clicking Create new app.

  3. On your app's page, click More, click View Webhooks, and then click Create Webhook.

  4. On the New Webhook popup, enter a name in the Webhook Name field and enter the URL provided by the ngrok agent to expose your application to the internet in the Payload URL field (i.e. https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app). URL to Publish

  5. Enter a 12345 in the Secret field, click the api:app and the api:build checkboxes under the Event Types section, and then click Add Webhook:

Run Webhooks with Heroku and ngrok​

Heroku sends different request body contents depending on the event that is being triggered. You can trigger a call from Heroku to your application by following the instructions below:

  1. Access Heroku and sign in using your Heroku account.

  2. On the Dashboard page, click your app name, click the Deploy tab, scroll down to the Manual deploy section, select a branch to deploy, and then click Deploy Branch.

    After the deployment finishes, confirm your localhost app receives a notification and logs both headers and body in the terminal.

Optionally, you can verify the log of the webhook call on your Heroku's page:

  1. On the Dashboard page, click your app name, click More, click View Webhooks, and then click the name of your webhook on the list of webhooks.

    Webhook Logs

Inspecting requests​

ngrok's Traffic Inspector captures all requests made through your ngrok endpoint to your localhost app. Click on any request to view detailed information about both the request and response.

info

By default, accounts only collect traffic metadata to avoid exposing secrets. You must enable full capture in the Observability section of your account settings to capture complete request and response data.

Use the traffic inspector to:

  • Validate webhook payloads and response data
  • Debug request headers, methods, and status codes
  • Troubleshoot integration issues without adding logging to your app

Replaying requests​

Test your webhook handling code without triggering new events from your service using the Traffic Inspector's replay feature:

  1. Send a test webhook from your service to generate traffic in your Traffic Inspector.

  2. Select the request you want to replay in the traffic inspector.

  3. Choose your replay option:

    • Click Replay to send the exact same request again
    • Select Replay with modifications to edit the request before sending

  4. Modify the request (optional): Edit any part of the original request, such as changing field values in the request body.

  5. Send the request by clicking Replay.

Your local application will receive the replayed request and log the data to the terminal.

Secure webhook requests​

The ngrok signature webhook verification feature allows ngrok to assert that requests from your Heroku webhook are the only traffic allowed to make calls to your localhost app.

Note: This ngrok feature is limited to 500 validations per month on free ngrok accounts. For unlimited, upgrade to Pro or Enterprise.

This is a quick step to add extra protection to your application.

  1. Create a file named heroku_policy.yml, replacing {your webhook secret} with the value you have entered in the Secret field during the webhook registration (See Integrate ngrok and Heroku.):

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  2. Restart your ngrok agent by running the command:

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  3. Access Heroku, sign in using your Heroku account, access your app, and then execute a new build.

Verify that your local application receives the request and logs information to the terminal.