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Guides

FastAPI HTTP Server

This guide explains how to create and deploy a Python FastAPI web app. To run this example, follow these steps:

1. Install the CLI and a container runtime engine, for example Docker. Use the unikraft CLI or the legacy kraft CLI.

2. Clone the examples repository and cd into the examples/httpserver-python3.12-FastAPI-0.121.3/ directory:

Code
git clone https://github.com/unikraft-cloud/examples
cd examples/httpserver-python3.12-FastAPI-0.121.3/

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:

Code
[●] Deployed successfully!
 │
 ├────── name: httpserver-python312-fastapi-01213-0n84f
 ├────── uuid: 5d7fc331-3c23-4953-b025-d152a872ea29
 ├───── metro: fra
 ├───── state: running
 ├──── domain: https://dry-water-0oexx89g.fra.unikraft.app
 ├───── image: httpserver-python312-fastapi-01213@sha256:fb2a00dcf1cfc3ac821cbda05f82f38d66e63121344b9bc60c6a6e2f11917b98
 ├─ boot time: 170.42 ms
 ├──── memory: 512 MiB
 ├─── service: dry-water-0oexx89g
 ├ private ip: 10.0.1.69
 └────── args: /usr/bin/python3 -m uvicorn src.server:app --host 0.0.0.0 --port 8080

In this case, the instance name is httpserver-python312-fastapi-01213-0n84f and the address is https://dry-water-0oexx89g.fra.unikraft.app. They're different for each run.

Use curl to query the Unikraft Cloud instance of the Python FastAPI web app server:

Code
curl https://dry-water-0oexx89g.fra.unikraft.app

Code
{"Hello":"World"}

You can list information about the instance by running:

Code
NAME                                      FQDN                                 STATE    STATUS   IMAGE                                        MEMORY   VCPUS  ARGS                                                 BOOT TIME
httpserver-python312-fastapi-01213-0n84f  dry-water-0oexx89g.fra.unikraft.app  standby  standby  httpserver-python312-fastapi-01213@sha25...  512 MiB  1      /usr/bin/python3 -m uvicorn src.server:app --hos...  169.45 ms

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 entry point for the app
• 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: base-compat:latest: The Unikraft runtime kernel to use is the latest that provides a minimal Linux-compatible environment.

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

• cmd: ["/usr/bin/python3", "-m", "uvicorn", "src.server:app", "--host", "0.0.0.0", "--port", "8080"]: Use this 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.

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-FastAPI-0.121.3 guide details the use of pip to deploy an app using the FastAPI framework on Unikraft Cloud.

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

Differences from the FastAPI 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 fastapi and uvicorn dependencies.

The Kraftfile is the same one used for httpserver-python3.12, except changed lines that have the following roles:

• cmd: ["/usr/bin/python3", "-m", "uvicorn", "src.server:app", "--host", "0.0.0.0", "--port", "8080"]: Use /usr/bin/python3 -m uvicorn src.server:app --host 0.0.0.0 --port 8080 as the starting command of the instance.

For Dockerfile newly added lines have the following roles:

• FROM python:3.12-bookworm AS build: 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 build.

• 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=build ...: Copy generated Python files in the new build image in the scratch-based image.

Similar actions apply to other pip3-based apps.

Learn more

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

Or visit the CLI Reference or the legacy CLI Reference.