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Python

This guide explains how to create and deploy a simple Python-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-python3.12/ directory:

Code(bash)
 
git clone https://github.com/kraftcloud/examples
cd examples/http-python3.12/

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: http-python312-ma2i9
 ├────────── uuid: e7389eee-9808-4152-b2ec-1f3c0541fd05
 ├───────── state: running
 ├─────────── url: https://young-night-5fpf0jj8.fra.unikraft.app
 ├───────── image: http-python312@sha256:278cb8b14f9faf9c2702dddd8bfb6124912d82c11b4a2c6590b6e32fc4049472
 ├───── boot time: 15.09 ms
 ├──────── memory: 512 MiB
 ├─────── service: young-night-5fpf0jj8
 ├── private fqdn: http-python312-ma2i9.internal
 ├──── private ip: 172.16.3.3
 └────────── args: /usr/bin/python /src/server.py

In this case, the instance name is http-python312-ma2i9 and the address is https://young-night-5fpf0jj8.fra.unikraft.app. They're different for each run.

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

Code(bash)
 
curl https://young-night-5fpf0jj8.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    CREATED AT    IMAGE                                        MEMORY   ARGS                            BOOT TIME
http-python312-ma2i9  young-night-5fpf0jj8.fra.unikraft.app  running  1 minute ago  http-python312@sha256:278cb8b14f9faf9c27...  512 MiB  /usr/bin/python /src/server.py  15094us

When done, you can remove the instance:

Code(bash)
 
kraft cloud instance remove http-python312-ma2i9

Customize your app

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

  • server.py: the actual Python HTTP server
  • Kraftfile: the Unikraft Cloud specification
  • Dockerfile: the Docker-specified app filesystem

Lines in the Kraftfile have the following roles:

  • spec: v0.6: The current Kraftfile specification version is 0.6.

  • runtime: python:3.12: The Unikraft runtime kernel to use is Python 3.12.

  • rootfs: ./Dockerfile: Build the app root filesystem using the Dockerfile.

  • cmd: ["/usr/bin/python3", "/src/server.py"]: Use /usr/bin/python3 /src/server.py as the starting command of the instance.

Lines in the Dockerfile have the following roles:

  • FROM scratch: Build the filesystem from the scratch container image, to create a base image.

  • COPY ./server.py /src/server.py: Copy the server implementation file (server.py) in the Docker filesystem (in /src/server.py).

The following options are available for customizing the app:

  • If you only update the implementation in the server.py 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). This includes the use of Python frameworks and the use of pip, as shown in the next section.

Using pip

pip is a package manager for Python. It's used to install dependencies for Python apps. pip uses the requirements.txt file to list required dependencies (with versions).

The http-python3.12-flask3.0 guide details the use of pip to deploy an app using the Flask framework on Unikraft Cloud.

Run the command below to deploy the app on Unikraft Cloud:

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

Differences from the http-python3.12 app are also the steps required to create an pip-based app:

  1. Add the requirements.txt file used by pip.

  2. Add framework-specific source files. In this case, this means the server.py file.

  3. Update the Dockerfile to:

    1. COPY the local files.

    2. RUN the pip3 install command to install dependencies.

    3. COPY of the resulting and required files (/usr/local/lib/pyhon3.12 and server.py) in the app filesystem, using the scratch container.

The following lists the files:

The requirements.txt file lists the flask dependency.

The Kraftfile is the same one used for http-python3.12.

For Dockerfile newly added lines have the following roles:

  • FROM python:3.12-bookworm AS base: Use the base image of the python:3.12-bookworm container. This provides the pip3 binary and other Python-related components. Name the current image base.

  • WORKDIR /app: Use /app as working directory. All other commands in the Dockerfile run inside this directory.

  • COPY requirements.txt /app: Copy the package configuration file to the Docker filesystem.

  • RUN pip3 install ...: Install pip components listed in requirements.txt.

  • COPY --from=base ...: Copy generated Python files in the new base image in the scratch-based image.

Similar actions apply to other pip3-based apps. See also the http-python3.12-django5.0 example.

Learn more

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

Code(bash)
 
kraft cloud --help

Or visit the CLI Reference.

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