# Flask and SQLite HTTP Server import { Tabs, TabsContent, TabsList, TabsTrigger } from "zudoku/ui/Tabs" {/* vale off */} {/* THIS FILE WAS AUTOGENERATED FROM THE PUBLIC EXAMPLE REPOSITORY. DO NOT EDIT THIS FILE DIRECTLY. */} This guide explains how to create and deploy a Python Flask app using SQLite. To run this example, follow these steps: 1. Install the CLI. Use the [unikraft CLI](/cli/unikraft) or the legacy [kraft CLI](https://unikraft.org/docs/cli/install). You need a [BuildKit](https://github.com/moby/buildkit) builder. The easiest way to get one is via [Docker](https://docs.docker.com/engine/install/). Alternatively, you can also directly set up and use BuildKit, see the [quick start](https://github.com/moby/buildkit#quick-start). :::note The unikraft CLI is the current standard, while kraft is the legacy version. Choose one of the CLIs below and only run the commands associated with it for the rest of this guide. ::: 2. Clone the [`examples` repository](https://github.com/unikraft-cloud/examples) and `cd` into the `examples/httpserver-python3.12-flask3.0-sqlite/` directory: ```bash git clone https://github.com/unikraft-cloud/examples cd examples/httpserver-python3.12-flask3.0-sqlite/ ``` Make sure to log into Unikraft Cloud and pick a [metro](/platform/metros) close to you. This guide uses `fra` (Frankfurt, 🇩🇪): ```bash title="unikraft" unikraft login ``` ```bash title="kraft" # 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: ```bash title="unikraft" unikraft build . --output /httpserver-python312-flask30-sqlite:latest unikraft run --scale-to-zero policy=on,cooldown-time=1000 --metro fra -p 443:8080/tls+http -m 768M --image /httpserver-python312-flask30-sqlite:latest ``` ```bash title="kraft" kraft cloud deploy --scale-to-zero on --scale-to-zero-cooldown 1s -p 443:8080/tls+http -M 768Mi . ``` The output shows the instance address and other details: ```ansi title="unikraft" metro: fra name: httpserver-python312-flask30-sqlite-qodkd uuid: e00e7aca-962d-409c-87c2-c245ca08b54b state: starting image: /httpserver-python312-flask30-sqlite resources: memory: 768MiB vcpus: 1 service: uuid: 1a2b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d name: lingering-orangutan-840mmdvd domains: - fqdn: lingering-orangutan-840mmdvd.fra.unikraft.app networks: - uuid: 2b3c4d5e-6f7a-8b9c-0d1e-2f3a4b5c6d7e private-ip: 10.0.3.3 mac: 12:b0:8a:4f:2c:91 timestamps: created: just now ``` ```ansi title="kraft" [●] Deployed successfully! │ ├───────── name: httpserver-python312-flask30-sqlite-qodkd ├───────── uuid: e00e7aca-962d-409c-87c2-c245ca08b54b ├──────── metro: https://api.fra.unikraft.cloud/v1 ├──────── state: starting ├─────── domain: https://lingering-orangutan-840mmdvd.fra.unikraft.app ├──────── image: oci://unikraft.io//httpserver-python312-flask30-sqlite@sha256:bdb0bf35a9675b9b3836cbb626606da0606334d91768c7ba31195c3062d6f517 ├─────── memory: 768 MiB ├────── service: lingering-orangutan-840mmdvd ├─ private fqdn: httpserver-python312-flask30-sqlite-qodkd.internal └─── private ip: 10.0.3.3 ``` In this case, the instance name is `httpserver-python312-flask30-sqlite-qodkd` and the address is `https://lingering-orangutan-840mmdvd.fra.unikraft.app`. They're different for each run. Use `curl` to query the Unikraft Cloud instance of the Python-based HTTP web server: ```bash curl https://young-night-5fpf0jj8.fra.unikraft.app ``` ```text [...]

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 ``` You can list information about the instance by running: ```bash title="unikraft" unikraft instances list ``` ```bash title="kraft" kraft cloud instance list ``` ```ansi title="unikraft" METRO NAME STATE IMAGE ARGS MEMORY VCPUS FQDN CREATED fra httpserver-python312-flask30-sqlite-qodkd running /httpserver-python312-flask30-sqlite 768MiB 1 lingering-orangutan-840mmdvd.fra.... 2 minutes ago ``` ```ansi title="kraft" NAME FQDN STATE STATUS IMAGE MEMORY VCPUS ARGS BOOT TIME httpserver-python312-flask30-sqlite-qodkd lingering-orangutan-840mmdvd.fra.... running 1 minute ago oci://unikraft.io//httpserver-python312-flask30-sqlite@sha256... 768 MiB 1 166.25 ms ``` When done, you can remove the instance: ```bash title="unikraft" unikraft instances delete httpserver-python312-flask30-sqlite-qodkd ``` ```bash title="kraft" kraft cloud instance remove httpserver-python312-flask30-sqlite-qodkd ``` ## Implementation details The app uses the following files: * `schema.sql`: SQL schema for the database * `init_db.py`: script to initialized the database file from `schema.sql` in `/app/database.db` * `server.py` + `templates/`: the actual Flask-based implementation: Python source code file and HTML template files * `requirements.txt`: `pip` configuration file to install required packages: Flask and SQLite * `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](https://erofs.docs.kernel.org/). * `cmd: ["/usr/bin/python3", "/app/server.py"]`: Use `/usr/bin/python3 /app/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](https://hub.docker.com/_/scratch/), to [create a base image](https://docs.docker.com/build/building/base-images/). * `COPY` rules copy required files. The process copies the `requirements.txt` file before running `pip3 install`. The process copies other files (including `schema.sql`, `init_db.py`) for the initialization of the database. * `RUN` commands trigger actions such as installing Python packages and initializing the database. * The new `scratch` image contains the relevant contents required by the app: * the SQLite dynamic library: `/usr/lib/x86_64-linux-gnu/libsqlite3.so.0` * the Python package files: `/usr/local/lib/python3.12` * the `/app` directory ## Customize your app To customize the app, update app files in the repository: * `schema.sql`: Update the database schema. * `server.py`, `templates/`: Update the Flask app.. * `requirements.txt`, `Dockerfile`: Update the list of Python packages used by the app. * `Kraftfile`: Update the command line used to start the app. The following options are available for customizing the app: * If you only update the implementation in the `server.py` source file or `template/` directory, and the database schema in `schema.sql`, 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`. * If you add new dependencies in `requirements.txt`, the `RUN pip3 install` in the `Dockerfile` command should take care of everything. It may be the case that you need to copy other files, such as the `/usr/lib/x86_64-linux-gnu/libsqlite3.so.0` for SQLite, via `COPY` commands in the `Dockerfile`. More extensive changes may require extending the `Dockerfile` ([see `Dockerfile` syntax reference](https://docs.docker.com/engine/reference/builder/)). * If you add a new Python source file that's running the `main()` function, update the `cmd` line in the `Kraftfile` and replace `server.py` to run that file when creating the instance. ## Learn more Use the `--help` option for detailed information on using Unikraft Cloud: ```bash title="unikraft" unikraft --help ``` ```bash title="kraft" kraft cloud --help ``` Or visit the [CLI Reference](/cli/unikraft) or the [legacy CLI Reference](/cli/kraft/overview). {/* vale on */}