Flatpak is a framework for distributing desktop applications and supported by most of Linux distributions. This talk shares how to package a HTTP server written in Python as a Flatpak app. And, runs it like a desktop application by launching a browser connecting to the server automatically. https://hackmd.io/@starnight/Have_an_HTTP_Server_in_Flatpak

1. Package a PyApp as a Flatpak Package:
An HTTP Server for Example
潘建宏 Jian-Hong Pan (StarNight)
@ PyCon APAC 2022 Lightning Talk

2. Who am I
潘建宏 / Jian-Hong Pan (StarNight)
Endless OS Foundation
You can find me at
● http://www.slideshare.net/chienhungpan/
● GitHub: starnight
● Email:
jhp [AT] endlessos.org
chienhung.pan [AT] gmail.com

3. Flatpak
Flatpak is a framework for distributing desktop applications across
various Linux distributions.
● Rootless install
● Sandboxed applications: Applications that are run with Flatpak
have limited access to the host environment.
● Desktop integration
● Delta updates
● Space efficiency: Flatpak deduplicates libraries (runtime) and other
files used by multiple applications
● Bundling: Allows application developers to ship almost any
dependency or library as part of their application.
● Branches: stable, beta

4. The Comparison Between Container and Flatpak
App1
Bins/Libs
Container Engine
App2
Bins/Libs
App3
Bins/Libs
Operating System
Containers
App1
Flatpak Runtimes provide
basic binaries and libraries
App2 App3
Operating System
Flatpaks

5. Install Flatpak
Some major Linux distributions, like Fodora, openSUSU and Endless OS
have already pre-installed flatpak.
● apt install flatpak flatpak-builder
● yum install flatpak flatpak-builder
● dnf install flatpak flatpak-builder
● pacman -S flatpak flatpak-builder
● apk add flatpak flatpak-builder
● …
Note: Not only x86(_64) platforms, but also arm64 and so on …

6. HTTP Server with Bottle
$ cat main.py
#!/bin/env python3
from bottle import Bottle, run
app = Bottle()
@app.route('/')
@app.route('/hello/<name>')
def hello(name='Stranger'):
return "Hello {}!".format(name)
run(app, host='localhost', port=8080)
$ cat requirements.txt
bottle

7. Now, Build as a Flatpak App
Flatpak’s Building Introduction

8. Get flatpak-pip-generator
Because the HTTP server is written in Python and depends on bottle, the
bottle must be installed as part of the flatpak app as well. So, we need
flatpak-builder-tools to generate the required module's meta
information for the flatpak’s manifest.
$ git clone https://github.com/flatpak/flatpak-builder-tools
$ pip install requirements-parser
PS. flatpak-builder-tools depends on requirements-parser

9. Generate Dependecy List
Use flatpak-pip-generator to generate the python3-requirements.json as
the module in the manifest io.github.starnight.http.yml.
$ ~/flatpak-builder-tools/pip/flatpak-pip-generator --requirements-file=requirements.txt
…
Running: "pip3 download --exists-action=i --dest
/tmp/pip-generator-python3-requirementsbfht6p35 -r requirements.txt"
Collecting bottle
Downloading bottle-0.12.23-py3-none-any.whl (90 kB)
…
Generating dependencies for bottle
Output saved to python3-requirements.json

10. $ cat python3-requirements.json
{
"name": "python3-bottle",
"buildsystem": "simple",
"build-commands": [
"pip3 install --verbose --exists-action=i --no-index --find-links="file://${PWD}"
--prefix=${FLATPAK_DEST} "bottle" --no-build-isolation"
],
"sources": [
{
"type": "file",
"url":
"https://files.pythonhosted.org/packages/63/96/2713bb6e0ca10ee2b7be568d6e6d112cf0a1b604
e14879fe744f48ebbed6/bottle-0.12.23-py3-none-any.whl",
"sha256": "9f1c363257c590bd34db5fad4693a7f06ff4217e9ad18337451de69c25137127"
}
]
}

11. Have the manifest io.github.starnight.http.yml
$ cat io.github.starnight.http.yml
app-id: io.github.starnight.http
runtime: org.freedesktop.Platform
runtime-version: '22.08'
sdk: org.freedesktop.Sdk
command: main.py
finish-args:
- --share=network
cleanup-commands:
- rm -rf /app/bin/__pycache__
(continue to right side)
modules:
- python3-requirements.json
- name: http
buildsystem: simple
build-commands:
- install -D main.py /app/bin/main.py
sources:
- type: file
path: main.py

12. The Runtime Environment
$ flatpak run --command=sh org.freedesktop.Sdk
[📦 org.freedesktop.Sdk ~]$ ls -l /bin/{python,pip}
-rwxr-xr-x 4 zack zack 221 Jan 1 1970 /bin/pip
lrwxrwxrwx 1 zack zack 7 Sep 3 20:34 /bin/python -> python3
$ flatpak run --command=sh org.freedesktop.Platform
[📦 org.freedesktop.Platform ~]$ ls -l /bin/python
lrwxrwxrwx 1 zack zack 7 Sep 3 20:35 /bin/python -> python3

13. Files in the Working Directory
$ ls -ltr
total 16
-rwxr-xr-x 1 zack zack 230 Sep 3 18:15 main.py
-rw-r--r-- 1 zack zack 7 Sep 3 18:15 requirements.txt
-rw-r--r-- 1 zack zack 564 Sep 3 18:31 python3-requirements.json
-rw-r--r-- 1 zack zack 417 Sep 3 20:03 io.github.starnight.http.yml
Original source files
Files for Flatpak packaging

14. Build the io.github.starnight.http as a flatpak app
$ flatpak-builder build-dir io.github.starnight.http.yml
Install the io.github.starnight.http flatpak app
● $ flatpak-builder build-dir
--force-clean --user --install io.github.starnight.http.yml

15. List Installed Flatpaks
$ flatpak list --columns=name,application,version,branch,origin
Name Application ID Version Branch Origin
http io.github.starnight.http master http-origin
Freedesktop Platform org.freedesktop.Platform 22.08.0 22.08 flathub
Mesa org.freedesktop.Platform.GL.default mesa-22.1.7 22.08 flathub
Intel org.freedesktop.Platform.VAAPI.Intel 22.08 flathub
openh264 org.freedesktop.Platform.openh264 2.1.0 2.0 flathub
openh264 org.freedesktop.Platform.openh264 2.1.0 2.3.0 flathub
Freedesktop SDK org.freedesktop.Sdk 22.08.0 22.08 flathub

16. Check the io.github.starnight.http Flatpak App
$ flatpak info io.github.starnight.http
ID: io.github.starnight.http
Ref: app/io.github.starnight.http/x86_64/master
Arch: x86_64
Branch: master
Origin: http-origin
Collection:
Installation: user
Installed: 459.8 kB
Runtime: org.freedesktop.Platform/x86_64/22.08
Sdk: org.freedesktop.Sdk/x86_64/22.08
Commit: b2c495a50e9b586dd07065246cb935baed02a2402526966b23ce4561b17802e6
Subject: Export io.github.starnight.http
Date: 2022-09-03 12:36:39 +0000

17. Run the io.github.starnight.http Flatpak App
$ flatpak run io.github.starnight.http
Bottle v0.12.23 server starting up (using WSGIRefServer())...
Listening on http://localhost:8080/
Hit Ctrl-C to quit.
127.0.0.1 - - [03/Sep/2022 20:43:40] "GET / HTTP/1.1" 200 15
127.0.0.1 - - [03/Sep/2022 20:43:40] "GET /favicon.ico HTTP/1.1" 404 742
$ flatpak run --command=sh io.github.starnight.http
[📦 io.github.starnight.http ~]$ ls /app/bin/
bottle.py main.py

18. More like a Desktop Application

19. The Idea is …
We need .desktop as the desktop launcher and an icon.
1. User clicks the launcher.
2. Execute the HTTP server.
3. Open the browser and browse http://localhost:8080 automatically.
We can use the XDG feature to lauch the browser with the
command “xdg-open http://localhost:8080”.
$ cat run.sh
#!/usr/bin/sh
main.py &
xdg-open http://localhost:8080

20. Desktop Launcher
$ cat io.github.starnight.http.desktop
[Desktop Entry]
Name=flatpak-http
Exec=run.sh
Terminal=false
Type=Application
StartupNotify=true
MimeType=text/plain;
# TRANSLATORS: Do NOT translate or transliterate this text!
# This is an icon file name.
Icon=io.github.starnight.http

21. Icon
Choose an SVG icon and save it as io.github.starnight.http.svg.
Source: https://www.pngrepo.com/svg/340417/http

22. Modify the manifest io.github.starnight.http.yml
● The command becomes run.sh
● Install the desktop launcher io.github.starnight.http.desktop, the
icon io.github.starnight.http.svg and the script run.sh into proper
lcoation.

23. $ cat io.github.starnight.http.yml
app-id: io.github.starnight.http
runtime: org.freedesktop.Platform
runtime-version: '22.08'
sdk: org.freedesktop.Sdk
command: run.sh
finish-args:
- --share=network
cleanup-commands:
- rm -rf /app/bin/__pycache__

24. modules:
- python3-requirements.json
- name: http
buildsystem: simple
build-commands:
- install -D main.py /app/bin/main.py
- install -D run.sh /app/bin/run.sh
- mkdir -p /app/share/applications
- install -D io.github.starnight.http.desktop /app/share/applications/io.github.starnight.http.desktop
- mkdir -p /app/share/icons/hicolor/scalable/apps
- install -D io.github.starnight.http.svg /app/share/icons/hicolor/scalable/apps/
sources:
- type: file
path: main.py
- type: file
path: run.sh
- type: file
path: io.github.starnight.http.desktop
- type: file
path: io.github.starnight.http.svg

25. Build & Run Again
$ flatpak-builder build-dir --user --install --force-clean io.github.starnight.http.yml
$ flatpak run io.github.starnight.http

26. Reference
● Flatpak’s documents
○ Basic concepts
○ Building your first Flatpak
○ Manifests
○ Sandbox Permissions
○ Python
● Flathub
● Have an HTTP Server in Flatpak

27. Thanks for Your Attention ~