This guide explains how to create and deploy a simple Perl-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-perl5.42/ directory:

   git clone https://github.com/unikraft-cloud/examples
   cd examples/httpserver-perl5.42/

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-perl542:latest
unikraft run --metro fra \
  -m 512M \
  -p 443:8080/tls+http \
  --scale-to-zero policy=on,cooldown-time=1000 \
  --image <my-org>/httpserver-perl542:latest

or

Using the legacy kraft CLI

kraft cloud deploy \
  -M 512Mi \
  -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-perl542-xue8j
uuid:         59d08bbc-cbb7-4c6b-a2cb-847828845db9
state:        starting
image:        <my-org>/httpserver-perl542
resources:
  memory:     512MiB
  vcpus:      1
service:
  uuid:       b62c0c0a-2de6-9068-1e93-223fa8f1edbf
  name:       fragrant-water-wau08gaw
  domains:
  - fqdn:     fragrant-water-wau08gaw.fra.unikraft.app
networks:
- uuid:       22bdfc9c-2f69-eb7e-5b5e-929aba51a2c0
  private-ip: 10.0.1.161
  mac:        12:b0:d4:aa:c1:98
timestamps:
  created:    just now

or

Using the legacy kraft CLI

[●] Deployed successfully!
 │
 ├───────── name: httpserver-perl542-xue8j
 ├───────── uuid: 59d08bbc-cbb7-4c6b-a2cb-847828845db9
 ├──────── metro: https://api.fra.unikraft.cloud/v1
 ├──────── state: starting
 ├─────── domain: https://fragrant-water-wau08gaw.fra.unikraft.app
 ├──────── image: oci://unikraft.io/<my-org>/httpserver-perl542@sha256:af86e8f03c0d4cfd596ccfd9a9d18ea75ac68c996c9cde31f64db24dc11100fe
 ├─────── memory: 512 MiB
 ├────── service: fragrant-water-wau08gaw
 ├─ private fqdn: httpserver-perl542-xue8j.internal
 └─── private ip: 10.0.1.161

In this case, the instance name is httpserver-perl542-xue8j and the address is https://fragrant-water-wau08gaw.fra.unikraft.app. They're different for each run.

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

curl https://fragrant-water-wau08gaw.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-perl542-xue8j  standby  <my-org>/httpserver-perl542        512MiB  1      fragrant-water-wau08gaw.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-perl542-xue8j  fragrant-water-wau08gaw.fra.unikraft.app  standby  standby  oci://unikraft.io/<my-org>/httpserver-perl542@sha256:...  512 MiB  1            109.46 ms

When you list your instances, you might notice they show as standby. This is normal behavior and means the instance is using Unikraft Cloud's scale-to-zero feature that saves resources when there is no traffic. To check your instance is working, open two terminals and use these commands to watch the status:

Using the unikraft CLI (Recommended)

unikraft instance list --watch
# In another terminal, make requests
curl https://fragrant-water-wau08gaw.fra.unikraft.app

or

Using the legacy kraft CLI

watch -n 1 "kraft cloud instance list"
# In another terminal, make requests
curl https://fragrant-water-wau08gaw.fra.unikraft.app

It switches to "running" then back to "standby."

When done, you can remove the instance:

Using the unikraft CLI (Recommended)

unikraft instances delete httpserver-perl542-xue8j

or

Using the legacy kraft CLI

kraft cloud instance remove httpserver-perl542-xue8j

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

• server.pl: the actual Perl 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 server.pl 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.