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KraftCloud

Run a Perl app

In this guide we create and deploy a simple Perl-based HTTP web server. To run this example, follow these steps:

  1. Install the kraft CLI tool and a container runtime engine, e.g. Docker.

  2. Clone the examples repository and cd into the examples/http-perl5.38/ directory:

Terminal window
git clone https://github.com/kraftcloud/examples
cd examples/http-perl5.38/

Make sure to log into KraftCloud by setting your token and a metro close to you. We use fra0 (Frankfurt, 🇩🇪) in this guide:

Terminal window
# Set KraftCloud access token
export KRAFTCLOUD_TOKEN=token
# Set metro to Frankfurt, DE
export KRAFTCLOUD_METRO=fra0

When done, invoke the following command to deploy this application on KraftCloud:

Terminal window
kraft cloud deploy -p 443:8080 -M 512 .

The output shows the instance URL and other details:

Terminal window
[●] Deployed successfully!
 │
 ├────────── name: http-perl538-1p4ml
 ├────────── uuid: eabb0080-0065-40ff-81a8-f790f1b218ee
 ├───────── state: running
 ├─────────── url: https://cold-brook-ba71jc16.fra0.kraft.host
 ├───────── image: http-perl538@sha256:8c2c1f536b349c24e04ab4fec508b69f7f2349302d42a02855318ee55c12e37c
 ├───── boot time: 64.56 ms
 ├──────── memory: 512 MiB
 ├─ service group: cold-brook-ba71jc16
 ├── private fqdn: http-perl538-1p4ml.internal
 ├──── private ip: 172.16.3.3
 └────────── args: /usr/bin/perl /usr/src/server.pl

In this case, the instance name is http-perl538-1p4ml and the URL is https://cold-brook-ba71jc16.fra0.kraft.host. They are different for each run.

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

Terminal window
curl https://cold-brook-ba71jc16.fra0.kraft.host
Hello, World!

At any point in time, you can list information about the instance:

Terminal window
kraft cloud instance list
NAME                FQDN                                  STATE    CREATED AT      IMAGE                                                     MEMORY   ARGS                              BOOT TIME
http-perl538-1p4ml  cold-brook-ba71jc16.fra0.kraft.host  stopped  37 seconds ago  razvan.unikraft.io/http-perl538@sha256:8c2c1f536b349c...  512 MiB  /usr/bin/perl /usr/src/server.pl  64556us

When done, you can remove the instance:

Terminal window
kraft cloud instance remove http-perl538-1p4ml

Customize your Application

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

  • server.pl: the actual Perl HTTP server
  • Kraftfile: the KraftCloud specification
  • Dockerfile: the Docker-specified application filesystem
#!/usr/bin/perl


use warnings;
use strict;


use HTTP::Daemon;
use HTTP::Status;
use HTTP::Response;


my $daemon = HTTP::Daemon->new(
        LocalAddr => '0.0.0.0',
        LocalPort => 8080,
) or die;


while (my $client_connection = $daemon->accept) {
        my $request = $client_connection->get_request;
        my $response = HTTP::Response->new(200);
        $response->content("Hello, World!\n");
        $client_connection->send_response($response);
}

The following options are available for customizing the application:

  • If only updating the implementation in the server.pl source file, no other change is required.

  • If new files are added, these have to be copied in the application filesystem, using the COPY command in the Dockerfile.

  • If a new Perl source files is added, update the cmd line in the Kraftfile and replace server.pl to run that file when creating the instance.

  • More extensive changes may require expanding the Dockerfile with additional Dockerfile commands.

Learn More

Use the --help option for detailed information on using KraftCloud:

Terminal window
kraft cloud --help

Or visit the CLI Reference.