This example shows how to build a simple GitHub Webhook receiver using Node.js with Express and run it on Unikraft Cloud. A webhook, also called a reverse API, is a way for a server to send real-time data to other applications when a specific event occurs. In this case, the webhook receiver listens for GitHub events, such as push events or pull request events, and logs them to the console.

To run this example, follow these steps:

1. Install the CLI. Use the unikraft CLI or the legacy kraft CLI. You need a BuildKit builder. The easiest way to get one is via Docker. Alternatively, you can also directly set up and use BuildKit, see the quick start.

   Note: The unikraft CLI is the current standard, while kraft is the legacy version. Choose one of the CLIs below and only run the commands associated with it for the rest of this guide.

2. Clone the examples repository and cd into the examples/github-webhook-node/ directory:

   git clone https://github.com/unikraft-cloud/examples
   cd examples/github-webhook-node/

Make sure to log into Unikraft Cloud and pick a metro close to you. This guide uses fra (Frankfurt, 🇩🇪):

Using the unikraft CLI (Recommended)

unikraft login

or

Using the legacy kraft CLI

# Set Unikraft Cloud access token
export UKC_TOKEN=token
# Set metro to Frankfurt, DE
export UKC_METRO=fra

When done, invoke the following command to deploy this app on Unikraft Cloud:

Using the unikraft CLI (Recommended)

unikraft build . --output <my-org>/github-webhook-node:latest
unikraft run --metro fra \
  -m 1G \
  -p 443:3000/tls+http \
  --scale-to-zero policy=on,cooldown-time=1000,stateful=true \
  -e GITHUB_WEBHOOK_SECRET=your_secret_here \
  --image <my-org>/github-webhook-node:latest

or

Using the legacy kraft CLI

kraft cloud deploy \
  -M 1Gi \
  -p 443:3000/tls+http \
  --scale-to-zero on \
  --scale-to-zero-stateful \
  --scale-to-zero-cooldown 1s \
  -e GITHUB_WEBHOOK_SECRET=your_secret_here \
  .

GITHUB_WEBHOOK_SECRET is the secret used to verify incoming webhook requests from GitHub. Set it to a string with high entropy.

The output shows the instance address and other details:

Using the unikraft CLI (Recommended)

metro:        fra
name:         github-webhook-node-bzq7u
uuid:         8a8634f1-fc78-4cc0-aa36-8f082d8a59f5
state:        starting
image:        <my-org>/github-webhook-node
resources:
  memory:     1024MiB
  vcpus:      1
service:
  uuid:       67c7cca2-ca82-1467-e2f1-1b455edb638c
  name:       dry-cloud-uuw0qlb6
  domains:
  - fqdn:     dry-cloud-uuw0qlb6.fra.unikraft.app
networks:
- uuid:       6153b689-b713-97c3-f8bb-bd08cc47f6bc
  private-ip: 10.0.1.205
  mac:        12:b0:d0:97:b0:d2
timestamps:
  created:    just now

or

Using the legacy kraft CLI

[●] Deployed successfully!
 │
 ├───────── name: github-webhook-node-bzq7u
 ├───────── uuid: 8a8634f1-fc78-4cc0-aa36-8f082d8a59f5
 ├──────── metro: https://api.fra.unikraft.cloud/v1
 ├──────── state: starting
 ├─────── domain: https://dry-cloud-uuw0qlb6.fra.unikraft.app
 ├──────── image: oci://unikraft.io/<my-org>/github-webhook-node@sha256:10974aac67ce6355148e21d91f918960bf0af29ad840fffeeb2fd01f8c905f66
 ├─────── memory: 1024 MiB
 ├────── service: dry-cloud-uuw0qlb6
 ├─ private fqdn: github-webhook-node-bzq7u.internal
 └─── private ip: 10.0.1.205

In this case, the instance name is github-webhook-node-bzq7u and the address is https://dry-cloud-uuw0qlb6.fra.unikraft.app. They're different for each run.

Use curl to query the Unikraft Cloud instance of the Node.js webhook server's health endpoint:

curl https://dry-cloud-uuw0qlb6.fra.unikraft.app/health

{"status":"healthy","timestamp":"2025-12-17T14:55:20.953Z","uptime":0.063799807}

The uptime field is so small because Unikraft Cloud scales the instance to zero when no connections are active. When a request comes in, Unikraft Cloud automatically starts the instance.

To see the incoming webhook events (you set up the webhook in GitHub), you can retrieve the logs of the instance by running:

Using the unikraft CLI (Recommended)

unikraft instances logs github-webhook-node-bzq7u

or

Using the legacy kraft CLI

kraft cloud instance logs github-webhook-node-bzq7u --follow

[2025-12-17T15:20:54.524Z] Webhook received: ping
{
  "timestamp": "2025-12-17T15:20:54.524Z",
  "event": "ping",
  "data": {
    "zen": "Accessible for all.",
    ...
  },
  "receivedAt": 1765984854525
}
...

GitHub sends the ping event when you set up the webhook. You can list information about the instance by running:

Using the unikraft CLI (Recommended)

unikraft instances list

METRO  NAME                       STATE    IMAGE                         ARGS  MEMORY  VCPUS  FQDN                                 CREATED
fra    github-webhook-node-bzq7u  standby  <my-org>/github-webhook-node        1.0GiB  1      dry-cloud-uuw0qlb6.fra.unikraft.app  2 minutes ago

or

Using the legacy kraft CLI

kraft cloud instance list

NAME                       FQDN                                 STATE    STATUS   IMAGE                                                      MEMORY   VCPUS  ARGS  BOOT TIME
github-webhook-node-bzq7u  dry-cloud-uuw0qlb6.fra.unikraft.app  standby  standby  oci://unikraft.io/<my-org>/github-webhook-node@sha256:...  1.0 GiB  1            197.47 ms

When done, you can remove the instance:

Using the unikraft CLI (Recommended)

unikraft instances delete github-webhook-node-bzq7u

or

Using the legacy kraft CLI

kraft cloud instance remove github-webhook-node-bzq7u

To test the GitHub webhook receiver, you must set up a webhook in a GitHub repository. Make sure to set the payload address to the Unikraft Cloud instance webhook, in this case https://dry-cloud-uuw0qlb6.fra.unikraft.app/webhook/github. You should also set the content type to application/json and select the events you want to receive. Lastly, you should set the secret to verify that the requests come from GitHub and weren't tampered with. Now, once you make changes in the repository (that you are listening to), you should see the webhook events logged in the instance logs:

Using the unikraft CLI (Recommended)

unikraft instances logs github-webhook-node-bzq7u

or

Using the legacy kraft CLI

kraft cloud instance logs github-webhook-node-bzq7u --follow

[2025-12-17T17:28:51.136Z] Webhook received: push
{
  "timestamp": "2025-12-17T17:28:51.136Z",
  "event": "push",
  "data": {
    "ref": "refs/heads/main",
    "before": "3312f99896b85e896f730d246180979553748f9d",
    "after": "12b2962bbc70f92fa33e4b30c0e1a3ed5f35f9d4",
    "repository": {
      "id": 123456789,
      "name": "your-repo",
      ...
    },
    ...
  },
  "receivedAt": 1765992531136
}

To customize the app, update the files in the repository, listed below:

• server.js: The Node.js Express web server that handles GitHub webhook events
• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified app filesystem

Use the --help option for detailed information on using Unikraft Cloud:

Using the unikraft CLI (Recommended)

unikraft --help

or

Using the legacy kraft CLI

kraft cloud --help

Or visit the CLI Reference or the legacy CLI Reference.