# Python HTTP Server

import { Tabs, TabsContent, TabsList, TabsTrigger } from "zudoku/ui/Tabs"

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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](/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/` directory:

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

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

<CodeTabs syncKey="cli">

```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
```

</CodeTabs>

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

<CodeTabs syncKey="cli">

```bash title="unikraft"
unikraft build . --output <my-org>/httpserver-python312:latest
unikraft run --scale-to-zero policy=on,cooldown-time=1000 --metro fra -p 443:8080/tls+http -m 512M --image <my-org>/httpserver-python312:latest
```

```bash title="kraft"
kraft cloud deploy --scale-to-zero on --scale-to-zero-cooldown 1s -p 443:8080/tls+http -M 512Mi .
```

</CodeTabs>

The output shows the instance address and other details:

<CodeTabs syncKey="cli">

```ansi title="unikraft"
metro:        fra
name:         httpserver-python312-ma2i9
uuid:         e7389eee-9808-4152-b2ec-1f3c0541fd05
state:        starting
image:        <my-org>/httpserver-python312
resources:
  memory:     512MiB
  vcpus:      1
service:
  uuid:       51a41f63-7e88-c443-b9bf-83cd7c04d975
  name:       young-night-5fpf0jj8
  domains:
  - fqdn:     young-night-5fpf0jj8.fra.unikraft.app
networks:
- uuid:       53da3490-c6f5-3718-25f1-219a65163c73
  private-ip: 10.0.3.3
  mac:        12:b0:18:0c:cb:aa
timestamps:
  created:    just now
```

```ansi title="kraft"
[●] Deployed successfully!
 │
 ├───────── name: httpserver-python312-ma2i9
 ├───────── uuid: e7389eee-9808-4152-b2ec-1f3c0541fd05
 ├──────── metro: https://api.fra.unikraft.cloud/v1
 ├──────── state: starting
 ├─────── domain: https://young-night-5fpf0jj8.fra.unikraft.app
 ├──────── image: oci://unikraft.io/<my-org>/httpserver-python312@sha256:278cb8b14f9faf9c2702dddd8bfb6124912d82c11b4a2c6590b6e32fc4049472
 ├─────── memory: 512 MiB
 ├────── service: young-night-5fpf0jj8
 ├─ private fqdn: httpserver-python312-ma2i9.internal
 └─── private ip: 10.0.3.3
```

</CodeTabs>

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:

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

```text
Hello, World!
```

You can list information about the instance by running:

<CodeTabs syncKey="cli">

```bash title="unikraft"
unikraft instances list
```

```bash title="kraft"
kraft cloud instance list
```

</CodeTabs>

<CodeTabs syncKey="cli">

```ansi title="unikraft"
METRO  NAME                        STATE    IMAGE                          ARGS  MEMORY  VCPUS  FQDN                                   CREATED
fra    httpserver-python312-ma2i9  running  <my-org>/httpserver-python312        512MiB  1      young-night-5fpf0jj8.fra.unikraft.app  2 minutes ago
```

```ansi title="kraft"
NAME                        FQDN                                   STATE    STATUS        IMAGE                                                       MEMORY   VCPUS  ARGS  BOOT TIME
httpserver-python312-ma2i9  young-night-5fpf0jj8.fra.unikraft.app  running  1 minute ago  oci://unikraft.io/<my-org>/httpserver-python312@sha256:...  512 MiB  1            15.09 ms
```

</CodeTabs>

When done, you can remove the instance:

<CodeTabs syncKey="cli">

```bash title="unikraft"
unikraft instances remove httpserver-python312-ma2i9
```

```bash title="kraft"
kraft cloud instance remove httpserver-python312-ma2i9
```

</CodeTabs>

## 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](https://erofs.docs.kernel.org/).

* `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](https://hub.docker.com/_/scratch/), to [create a base image](https://docs.docker.com/build/building/base-images/).

* `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](https://docs.docker.com/engine/reference/builder/)).
  This includes the use of Python frameworks and the use of `pip`, as shown in the next section.

## Using `pip`

[`pip`](https://pip.pypa.io/en/stable/) 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`](https://github.com/unikraft-cloud/examples/tree/main/httpserver-python3.12-flask3.0) guide details the use of `pip` to deploy an app using the [`Flask`](https://flask.palletsprojects.com/en/3.0.x/) framework on Unikraft Cloud.

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

<CodeTabs syncKey="cli">

```bash title="unikraft"
unikraft build . --output <my-org>/httpserver-python312-flask30:latest
unikraft run --scale-to-zero policy=on,cooldown-time=1000 --metro fra -p 443:8080/tls+http -m 512M --image <my-org>/httpserver-python312-flask30:latest
```

```bash title="kraft"
kraft cloud deploy --scale-to-zero on --scale-to-zero-cooldown 1s -p 443:8080/tls+http -M 512Mi .
```

</CodeTabs>

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](https://hub.docker.com/_/scratch/).

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`](https://github.com/unikraft-cloud/examples/tree/main/httpserver-python3.12-django5.0) example.

## Learn more

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

<CodeTabs syncKey="cli">

```bash title="unikraft"
unikraft --help
```

```bash title="kraft"
kraft cloud --help
```

</CodeTabs>

Or visit the [CLI Reference](/cli/unikraft) or the [legacy CLI Reference](/cli/kraft/overview).
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