# My app deployment failed because of a health check

As an app is deployed, App Platform verifies that its components are healthy by checking their availability on the app’s TCP port (the default port is `8080`). If the app is not available on that port, then the health check fails and the app rolls back to the last healthy deployment.

There are two common issues that cause an app to fail a health check:

- The app starts on a different port than App Platform expects, such as starting on port `3000` when App Platform expects that app to be available on port `8080`. You can change the port App Platform uses to perform health checks by editing the `http_port` field in your app’s spec file and uploading the new app spec.

To edit your app’s spec, navigate to your app’s **Overview** page and then click the **Settings** tab. Scroll down to the **App Spec** section and the click **Edit**. A preview of the spec opens. Click the **Download** link at the bottom of the preview window. The spec downloads to your local machine.

Open the spec in a text editor and edit the `http_port` field to port `8080`. Once you have edited the file, save it can close it.

Back in your app’s **Settings**, click **Upload File** in the **App Spec** section. Your machine’s local file manager opens. Select the updated spec file and click **Open**. The spec uploads to App Platform and triggers a new build.

- The app’s HTTP server is configured to listen for HTTP requests on address `localhost` or `127.0.0.1`. This is common on NodeJS apps. These addresses use a loopback network interface that is only accessible from within the app’s container and are not accessible to external network traffic.

If your app is configured to listen on a different HTTP endpoint than the app’s root endpoint, you can configure the health checks feature to check your defined endpoint.

To change your app’s health check endpoint, navigate to your app’s **Overview** page and then click the **Settings** tab. Select the component that requires the health check and then scroll down to the **Health Checks** section. Click **Edit**.

In the Health Check section, click **HTTP** and then enter the endpoint you want to monitor into the **HTTP Path** field. Click **Save**. This automatically trigger a new build.

## Related Topics

[How do I fix the error "Record is managed by an App on this account, and cannot be deleted"?](https://docs.digitalocean.com/support/how-do-i-fix-the-error-record-is-managed-by-an-app-on-this-account-and-cannot-be-deleted/index.html.md): Use the app’s Settings tab to remove domains associated with App Platform apps.

[Why do I get the error “JavaScript heap out of memory” during deployment?](https://docs.digitalocean.com/support/why-do-i-get-the-error-javascript-heap-out-of-memory-during-deployment/index.html.md): Increase the heap memory by setting the environment variable NODE\_OPTIONS=–max-old-space-size=4096.

[How do I fix a "permission denied for schema public" error in my dev database?](https://docs.digitalocean.com/support/how-do-i-fix-a-permission-denied-for-schema-public-error-in-my-dev-database/index.html.md): Delete the existing dev database and create a new one. Then make sure that the app deployment completes successfully.