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Express HTTP Server

Express is a fast, unopinionated, minimalist web framework for Node.js.

To run this example, follow these steps:

1. Install the CLI and a container runtime engine, for example Docker. Use the unikraft CLI or the legacy kraft CLI.

2. Clone the examples repository and cd into the examples/httpserver-expressjs4.18-node21 directory:

Code
git clone https://github.com/unikraft-cloud/examples
cd examples/httpserver-expressjs4.18-node21/

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

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

The output shows the instance address and other details:

Code
[●] Deployed successfully!
 │
 ├────────── name: httpserver-expressjs4.18-node21-lb3p2
 ├────────── uuid: a1b2c3d4-e5f6-7890-abcd-ef1234567890
 ├───────── state: starting
 ├──────── domain: https://calm-ocean-r9x4mk7v.fra.unikraft.app
 ├───────── image: httpserver-expressjs4.18-node21@sha256:2e7d3f1a9c4b8e05d6f2a3b7c1e4d8f0a2b5c9e3d7f1a4b8
 ├──────── memory: 512 MiB
 ├─────── service: calm-ocean-r9x4mk7v
 ├── private fqdn: httpserver-expressjs4.18-node21-lb3p2.internal
 ├──── private ip: 172.16.3.4
 └────────── args: /usr/bin/node /usr/src/server.js

In this case, the instance name is httpserver-expressjs4.18-node21-lb3p2 and the address is https://calm-ocean-r9x4mk7v.fra.unikraft.app. They're different for each run.

Use curl to query the Unikraft Cloud instance of the Express.js-based HTTP web server:

Code
curl https://calm-ocean-r9x4mk7v.fra.unikraft.app

Code
Hello, World!

You can list information about the instance by running:

Code
NAME                                   FQDN                        STATE    STATUS       IMAGE                                        MEMORY   VCPUS  ARGS                              BOOT TIME
httpserver-expressjs4.18-node21-lb3p2  calm-ocean-r9x4mk7v.fra...  running  since 3mins  httpserver-expressjs4.18-node21@sha256:2...  512 MiB  1      /usr/bin/node /usr/src/server.js  312.45 ms

When done, you can remove the instance:

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
• app/index.js: the Express.js server implementation

Lines in the Kraftfile have the following roles:

• spec: v0.6: The current Kraftfile specification version is 0.6.

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

• rootfs: ./Dockerfile: Build the app root filesystem using the Dockerfile.

• 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:21-alpine AS build: Build the app using the Node.js 21 Alpine image.

• COPY ...: Copy required files to the app filesystem: the node binary executable, libraries, configuration files, and the Express.js app.

• RUN npm install: Install Express.js and other dependencies.

The following options are available for customizing the app:

• If you only update the implementation in the app/index.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 app/index.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

• Express's Documentation
• Unikraft Cloud's Documentation
• Building Dockerfile images with Buildkit

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

Or visit the CLI Reference or the legacy CLI Reference.