This guide explains how to create and deploy a simple Erlang-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 examples repository and cd into the examples/httpserver-erlang26.2/ directory:

   git clone https://github.com/unikraft-cloud/examples
   cd examples/httpserver-erlang26.2/

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-erlang262:latest
unikraft run --metro fra \
  -m 512M \
  -p 443:8080/tls+http \
  --scale-to-zero policy=idle,cooldown-time=1000,stateful=true \
  --image <my-org>/httpserver-erlang262:latest

or

Using the legacy kraft CLI

kraft cloud deploy \
  -M 512Mi \
  -p 443:8080/tls+http \
  --scale-to-zero idle \
  --scale-to-zero-stateful \
  --scale-to-zero-cooldown 1s \
  .

The output shows the instance address and other details:

Using the unikraft CLI (Recommended)

metro:        fra
name:         httpserver-erlang262-sw2bp
uuid:         1c4a8a51-fb61-45fc-87b8-26d192a7c2bc
state:        starting
image:        <my-org>/httpserver-erlang262
resources:
  memory:     512MiB
  vcpus:      1
service:
  uuid:       c7a6b443-c424-8a96-ce90-e833841b6eca
  name:       patient-field-ck629j2u
  domains:
  - fqdn:     patient-field-ck629j2u.fra.unikraft.app
networks:
- uuid:       6d767165-9196-e27d-bb12-5eb5a9188654
  private-ip: 10.0.3.3
  mac:        12:b0:05:ce:23:30
timestamps:
  created:    just now

or

Using the legacy kraft CLI

[●] Deployed successfully!
 │
 ├───────── name: httpserver-erlang262-sw2bp
 ├───────── uuid: 1c4a8a51-fb61-45fc-87b8-26d192a7c2bc
 ├──────── metro: https://api.fra.unikraft.cloud/v1
 ├──────── state: starting
 ├─────── domain: https://patient-field-ck629j2u.fra.unikraft.app
 ├──────── image: oci://unikraft.io/<my-org>/httpserver-erlang262@sha256:d99feefa7973ba43f726356497f54c34a16421aa25a27fa547d2c1add418204e
 ├─────── memory: 512 MiB
 ├────── service: patient-field-ck629j2u
 ├─ private fqdn: httpserver-erlang262-sw2bp.internal
 └─── private ip: 10.0.3.3

In this case, the instance name is httpserver-erlang262-sw2bp and the address is https://patient-field-ck629j2u.fra.unikraft.app. They're different for each run.

Use curl to query the Unikraft Cloud instance of the Erlang-based HTTP web server:

curl https://patient-field-ck629j2u.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-erlang262-sw2bp  running  <my-org>/httpserver-erlang262        512MiB  1      patient-field-ck629j2u.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-erlang262-sw2bp  patient-field-ck629j2u.fra.unikraft.app  running  since 35secs  oci://unikraft.io/<my-org>/httpserver-erlang262@sha256:...  512 MiB  1            404.04 ms

When done, you can remove the instance:

Using the unikraft CLI (Recommended)

unikraft instances delete httpserver-erlang262-sw2bp

or

Using the legacy kraft CLI

kraft cloud instance remove httpserver-erlang262-sw2bp

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

• http_server.erl: the actual Erlang HTTP server implementation
• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified app filesystem

The following options are available for customizing the app:

• If you only update the implementation in the http_server.erl 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.