Guides

Lua

In this guide we create and deploy a simple Lua-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-lua5.1/ directory:

Code
 
git clone https://github.com/kraftcloud/examples
cd examples/http-lua5.1/

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

Code
 
# Set Unikraft Cloud access token
export UKC_TOKEN=token
# Set metro to Frankfurt, DE
export UKC_METRO=fra0

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

Code
 
kraft cloud deploy -p 443:8080 .

The output shows the instance URL and other details:

Code
 
[●] Deployed successfully!
 │
 ├────────── name: http-lua51-ma2i9
 ├────────── uuid: e7389eee-9808-4152-b2ec-1f3c0541fd05
 ├───────── state: running
 ├─────────── url: https://young-night-5fpf0jj8.fra0.kraft.host
 ├───────── image: http-lua51@sha256:278cb8b14f9faf9c2702dddd8bfb6124912d82c11b4a2c6590b6e32fc4049472
 ├───── boot time: 15.09 ms
 ├──────── memory: 128 MiB
 ├─────── service: young-night-5fpf0jj8
 ├── private fqdn: http-lua51-ma2i9.internal
 ├──── private ip: 172.16.3.3
 └────────── args: /usr/bin/lua /http_server.lua

In this case, the instance name is http-lua51-ma2i9 and the URL is https://young-night-5fpf0jj8.fra0.kraft.host. They are different for each run.

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

Code
 
curl https://young-night-5fpf0jj8.fra0.kraft.host

Code
 
Hello, World!

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

Code
 
kraft cloud instance list

Code
 
NAME              FQDN                                  STATE    CREATED AT    IMAGE                                    MEMORY   ARGS                           BOOT TIME
http-lua51-ma2i9  young-night-5fpf0jj8.fra0.kraft.host  running  1 minute ago  http-lua51@sha256:278cb8b14f9faf9c27...  128 MiB  /usr/bin/lua /http_server.lua  15094us

When done, you can remove the instance:

Code
 
kraft cloud instance remove http-lua51-ma2i9

Customize your Application

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

• http_server.lua: the actual Lua HTTP server
• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified application filesystem

The following options are available for customizing the application:

• If only updating the implementation in the http_server.lua 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 Lua source files is added, update the cmd line in the Kraftfile and replace http_server.lua 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 Unikraft Cloud:

Code
 
kraft cloud --help

Or visit the CLI Reference.