Guides

Erlang

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 kraft CLI tool and a container runtime engine, for example Docker.

2. Clone the examples repository and cd into the examples/http-erlang26.2/ directory:

Code(bash)
 
git clone https://github.com/kraftcloud/examples
cd examples/http-erlang26.2/

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

Code(bash)
 
# 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:

Code(bash)
 
kraft cloud deploy -p 443:8080 -M 512 .

The output shows the instance address and other details:

Code(ansi)
 
[●] Deployed successfully!
 │
 ├────────── name: erlang-sw2bp
 ├────────── uuid: 1c4a8a51-fb61-45fc-87b8-26d192a7c2bc
 ├───────── state: starting
 ├──────── domain: https://patient-field-ck629j2u.fra.unikraft.app
 ├───────── image: erlang@sha256:d99feefa7973ba43f726356497f54c34a16421aa25a27fa547d2c1add418204e
 ├──────── memory: 512 MiB
 ├─────── service: patient-field-ck629j2u
 ├── private fqdn: erlang-sw2bp.internal
 ├──── private ip: 172.16.3.3
 └────────── args: /usr/bin/wrapper.sh /usr/bin/erl -noshell -s http_server

In this case, the instance name is erlang-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:

Code(bash)
 
curl https://patient-field-ck629j2u.fra.unikraft.app

Code(text)
 
Hello, World!

You can list information about the instance by running:

Code(bash)
 
kraft cloud instance list

Code(text)
 
NAME               FQDN                                    STATE    STATUS              IMAGE                                 MEMORY   ARGS                                                     BOOT TIME
erlang-sw2bp       patient-field-ck629jsu.fra.unikraft.app  running  since 35secs        erlang@sha256:d99feefa7973ba43f72...  512 MiB  /usr/bin/wrapper.sh /usr/bin/erl -noshell -s http_se...  404.04 ms

When done, you can remove the instance:

Code(bash)
 
kraft cloud instance remove erlang-sw2bp

Customize your app

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

• http_server.erl: the actual Erlang HTTP server
• 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).

Learn more

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

Code(bash)
 
kraft cloud --help

Or visit the CLI Reference.