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Example apps

Node HTTP Server

Node.js is a free, open source, cross-platform JavaScript runtime environment.

To run this example, follow these steps:

1. Install the unikraft 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.

2. Clone the examples repository and cd into the examples/httpserver-node26 directory:

   Code
   git clone https://github.com/unikraft-cloud/examples
   cd examples/httpserver-node26/

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

Code
unikraft login

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

Code
unikraft build . --output <my-org>/httpserver-node26:latest
unikraft run --metro fra \
  -m 512M \
  -p 443:8080/tls+http \
  --scale-to-zero policy=on,cooldown-time=1000 \
  --image <my-org>/httpserver-node26:latest

The output shows the instance address and other details:

Code
metro:        fra
name:         httpserver-node26-v8mp4
uuid:         c3d4e5f6-a7b8-9012-cdef-123456789012
state:        starting
image:        <my-org>/httpserver-node26
resources:
  memory:     512MiB
  vcpus:      1
service:
  uuid:       8c6367b6-d913-4b24-fbc4-922cf124c8f8
  name:       bright-star-k3m7pqnx
  domains:
  - fqdn:     bright-star-k3m7pqnx.fra.unikraft.app
networks:
- uuid:       229c5467-216f-79dd-e2f9-3307b196fad3
  private-ip: 10.0.3.6
  mac:        12:b0:25:ce:7f:75
timestamps:
  created:    just now

In this case, the instance name is httpserver-node26-v8mp4 and the address is https://bright-star-k3m7pqnx.fra.unikraft.app. They're different for each run.

Use curl to query the Unikraft Cloud instance of the Node.js HTTP server:

Code
curl https://bright-star-k3m7pqnx.fra.unikraft.app

Code
Hello, World!

You can list information about the instance by running:

Code
unikraft instances list

Code
METRO  NAME                     STATE    IMAGE                       ARGS  MEMORY  VCPUS  FQDN                                   CREATED
fra    httpserver-node26-v8mp4  running  <my-org>/httpserver-node26        512MiB  1      bright-star-k3m7pqnx.fra.unikraft.app  2 minutes ago

When done, you can remove the instance:

Code
unikraft instances delete httpserver-node26-v8mp4

Customize your app

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

• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified app filesystem
• server.js: the Node.js HTTP server implementation

Lines in the Kraftfile have the following roles:

• spec: v0.7: The current Kraftfile specification version is 0.7.

• runtime: base-compat:latest: The kernel to use.

• rootfs: Build the app root filesystem. source: ./Dockerfile means the filesystem is built using the Dockerfile. format: erofs means the filesystem type is EROFS.

• cmd: ["/usr/bin/node", "/usr/src/server.js"]: Use /usr/bin/node /usr/src/server.js as the starting command of the instance.

Lines in the Dockerfile have the following roles:

• FROM node:26-alpine AS node: Use the Node.js 26 Alpine image as the source for the node binary and libraries.

• FROM scratch: Build the runtime filesystem from a minimal base image.

• COPY ...: Copy required files to the app filesystem: the node binary executable, libraries, and the /usr/src/server.js implementation.

The following options are available for customizing the app:

• If you only update the implementation in the server.js source file, you don't need to make any other changes.

• If you want to add extra files, you need to copy them into the filesystem using the COPY command in the Dockerfile.

• If you want to replace server.js with a different source file, update the cmd line in the Kraftfile and replace /usr/src/server.js with the path to your new source file.

• More extensive changes may require extending the Dockerfile (see Dockerfile syntax reference).

Learn more

• Node.js's Documentation
• Unikraft Cloud's Documentation
• Building Dockerfile images with Buildkit

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

Code
unikraft --help

Or visit the CLI Reference.