Ceph

Python release lifecycle usually spans for 5 years. Python 3.6 was launched in Dec 2016 and was deprecated by Dec 2021. However 2 active Ceph releases are still based on that Python version (Pacific and Quincy). Ideally the Python interpreter version should be picked to couple with the Ceph release, meaning that:

• Pacific (2021 March-2023 Jun) should have been released with Python 3.8 (2019 Oct-2024 Oct) or Python 3.9 (2020 Oct-2025 Oct)
• Quincy (2022 Apr-2024 Jun) should have been released with Python 3.10 (2021 Oct-2026 Oct)

Impediments to the above approach:

• Ceph commits to support distros that don't follow the above cadence (e.g.: default CentOS 8 default Python is 3.6). However, in many cases these same distro provide newer versions via extra/non-official sources (EPEL, PPAs etc).
• While many supported distros support newer Python versions via extra packages, RPM-based distros (Fedora, CentOS, OpenSUSE, SEL) also require specific packages for each Python version (e.g.: python3-cherrypy in CentOS EPEL is for 3.6, so another python38-cherrypy package will be required for 3.8). Debian-like distros can share Python-only packages across multiple Python versions

Distro	Release	Lifecycle	Python 3.6	Python 3.7	Python 3.8	Python 3.9	Python 3.10
CentOS Stream	8		x (default)		x	x
CentOS Stream	9					x (default)
Ubuntu	20.04		x (default)		x	x
Ubuntu	22.04						x (default)
OpenSUSE Leap	15.2	EoL (2021-12)	x (default)
OpenSUSE Leap	15.3	2022-12	x (default)			x
OpenSUSE Leap	15.4	2023-12	x (default)			x	x
Debian	10			x (default)
Debian	11					x (default)

With the above table in main, if we move to Python 3.9:

• For Reef (main), we could still support:
  • CentOS Stream 9,
  • Ubuntu 20.04 (Surprisingly, Ubuntu 22.04 doesn't support Py3.9),
  • OpenSUSE Leap 15.4
  • Debian 11

• For Quincy, if we increase Python version to 3.9, we could maintain the currently supported distros:
  • CentOS Stream 8,
  • Ubuntu 20.04,
  • OpenSUSE Leap 15.3,
  • Debian 11

• For Pacific: let's not make any changes (support for Debian 10 and OpenSUSE Leap 15.2 makes it complicate to upgrade).

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And additional proposal would be to get rid of external (distro-packaged) deps and:

• Embed Python code in the repo (via git submodules or subtrees),
• Install at build time via pip (this is the way that Dashboard works for Front-end packages)

This would also require modifying the method PyModule::load in the file src/mgr/PyModule.cc to look for packages into the local directory (via sys.path): <mgr_module_path>/site-packages/ (or similar).