This guide explains how to create and deploy a simple C++-based HTTP web server. 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 example repository and cd into the examples/httpserver-gpp13.2/ directory:

   git clone https://github.com/unikraft-cloud/examples
   cd examples/httpserver-gpp13.2/

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>/httpserver-gpp132:latest
unikraft run --metro fra \
  -m 256M \
  -p 443:8080/tls+http \
  --scale-to-zero policy=on,cooldown-time=1000 \
  --image <my-org>/httpserver-gpp132:latest

or

Using the legacy kraft CLI

kraft cloud deploy \
  -M 256Mi \
  -p 443:8080/tls+http \
  --scale-to-zero on \
  --scale-to-zero-cooldown 1s \
  .

The output shows the instance address and other details:

Using the unikraft CLI (Recommended)

metro:        fra
name:         httpserver-gpp132-jzbuo
uuid:         b8e015fd-d006-49d5-849e-3fd497c9159a
state:        starting
image:        <my-org>/httpserver-gpp132
resources:
  memory:     256MiB
  vcpus:      1
service:
  uuid:       fd89859a-cf60-fa1f-1d43-0989a7c18b10
  name:       throbbing-wave-grxjih4t
  domains:
  - fqdn:     throbbing-wave-grxjih4t.fra.unikraft.app
networks:
- uuid:       636ebc7e-bf82-d71d-5432-5445084a4308
  private-ip: 10.0.6.5
  mac:        12:b0:0f:20:02:9d
timestamps:
  created:    just now

or

Using the legacy kraft CLI

[●] Deployed successfully!
 │
 ├───────── name: httpserver-gpp132-jzbuo
 ├───────── uuid: b8e015fd-d006-49d5-849e-3fd497c9159a
 ├──────── metro: https://api.fra.unikraft.cloud/v1
 ├──────── state: starting
 ├─────── domain: https://throbbing-wave-grxjih4t.fra.unikraft.app
 ├──────── image: oci://unikraft.io/<my-org>/httpserver-gpp132@sha256:a58873987104b52c13b79168a2e2f1a81876ba6efacd6dbc98e996afe5c09699
 ├─────── memory: 256 MiB
 ├────── service: throbbing-wave-grxjih4t
 ├─ private fqdn: httpserver-gpp132-jzbuo.internal
 └─── private ip: 10.0.6.5

In this case, the instance name is httpserver-gpp132-jzbuo and the address is https://throbbing-wave-grxjih4t.fra.unikraft.app. They're different for each run.

Use curl to query the Unikraft Cloud instance of the C++ HTTP web server:

curl https://throbbing-wave-grxjih4t.fra.unikraft.app

Hello, World!

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    httpserver-gpp132-jzbuo  running  <my-org>/httpserver-gpp132        256MiB  1      throbbing-wave-grxjih4t.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
httpserver-gpp132-jzbuo  throbbing-wave-grxjih4t.fra.unikraft.app  running  1 minute ago  oci://unikraft.io/<my-org>/httpserver-gpp132@sha256:...  256 MiB  1            15.61 ms

When done, you can remove the instance:

Using the unikraft CLI (Recommended)

unikraft instances delete httpserver-gpp132-jzbuo

or

Using the legacy kraft CLI

kraft cloud instance remove httpserver-gpp132-jzbuo

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

• http_server.cpp: the actual C++ HTTP server implementation
• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified app filesystem

Lines in the Kraftfile have the following roles:

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

• runtime: base: The Unikraft runtime kernel to use is its base one.

• 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: ["/http_server"]: Use /http_server as the starting command of the instance.

Lines in the Dockerfile have the following roles:

• FROM --platform=linux/x86_64 gcc:13.2.0-bookworm AS build: Build the filesystem from the bookworm gcc container image, to create a base image.

• COPY ./http_server.cpp /src/http_server.cpp: Copy the server implementation file (http_server.cpp) in the Docker filesystem (in /src/http_server.cpp).

The following options are available for customizing the app:

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

• If you create any new source files, copy them into the app filesystem by using the COPY command in the Dockerfile.

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

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.