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Guides

Python HTTP Server

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 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.

2. Clone the examples repository and cd into the examples/httpserver-python3.12/ directory:

Code
git clone https://github.com/unikraft-cloud/examples
cd examples/httpserver-python3.12/

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

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

The output shows the instance address and other details:

In this case, the instance name is httpserver-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:

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curl https://young-night-5fpf0jj8.fra.unikraft.app

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Hello, World!

You can list information about the instance by running:

When done, you can remove the instance:

Customize your app

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

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

Lines in the Kraftfile have the following roles:

• spec: v0.7: The current Kraftfile specification version is 0.7.

• runtime: base-compat:latest: The runtime kernel to use is the base compatibility kernel.

• rootfs: Build the app root filesystem. source: ./Dockerfile means the filesystem is built using the Dockerfile. format: erofs means the filesystem type is EROFS.

• 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 httpserver-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:

Differences from the httpserver-python3.12-flask3.0 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:

   3.1. COPY the local files.

   3.2. RUN the pip3 install command to install dependencies.

   3.3. COPY of the resulting and required files (/usr/local/lib/python3.12 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 httpserver-python3.12-flask3.0.

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 httpserver-python3.12-django5.0 example.

Learn more

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

Or visit the CLI Reference or the legacy CLI Reference.