Install of Matrix -Synapse failed

Troubleshooting
1

Hi,
I wanted to experiment with Matrix Synapse. For this purpose, I started with a fresh and up-to-date DietPi OS installation. The installation via dietpi-software was able to start, but the installation process aborted midway. An error was displayed, and the installation routine could not be completed successfully.

Is this a known issue, or has anyone experienced something similar?

BR
Lassa333

2

Nope. You could have filled the trouble shooting template. Or at least share an error message. Now, nobody can help you.

3

Details:

  • Date | 2026-01-25 14:45:40
  • Bug report | 090d4061-e419-4da5-afee-198a4bf55f30
  • Program name | DietPi-Software
  • Command | `python3 -m synapse.app.homeserver -H DietPi -c homeserver.yaml --generate-config --r
  • Exit code | 1
  • DietPi version | v9.20.1 (MichaIng/master)
  • Distro version | trixie (ID=8)
  • Kernel version | `Linux DietPi 6.12.63+deb13-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.12.63-1 (2025-12-30
  • Architecture | amd64
  • Hardware model | Virtual Machine (x86_64) (ID=20)
  • Power supply | (EG: RAVPower 5V 1A)
  • SD card | (EG: SanDisk Ultra 16 GB)

Steps to reproduce:

  1. New Dietpi v9.20.1 on a proxmox-VM
  2. Wanted to install Matrix-Synapse via “dietpi-software”

Expected behaviour:

  • Install Matrix-synase server

Actual behaviour:

  • Install-routine ended with this error-code (see below)

Extra details:

  • none

Additional logs:

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/usr/local/lib/python3.13/dist-packages/synapse/app/homeserver.py", line 32, in <module>
    from synapse import events
  File "/usr/local/lib/python3.13/dist-packages/synapse/events/__init__.py", line 46, in <module>
    from synapse.util.caches import intern_dict
  File "/usr/local/lib/python3.13/dist-packages/synapse/util/caches/__init__.py", line 34, in <module>
    from synapse.metrics import SERVER_NAME_LABEL
  File "/usr/local/lib/python3.13/dist-packages/synapse/metrics/__init__.py", line 265, in <module>
    class InFlightGauge(Generic[MetricsEntry], Collector):
    ...<132 lines>...
                yield gauge
  File "/usr/lib/python3.13/typing.py", line 2071, in __new__
    return super().__new__(mcls, name, bases, namespace, **kwargs)
           ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen abc>", line 106, in __new__
TypeError: Cannot create a consistent method resolution order (MRO) for bases Generic, Collector
4

Yes, a bug of one of matrix synapse dependencies: python-prometheus_client.
https://github.com/element-hq/synapse/issues/19375
https://github.com/element-hq/synapse/issues/19382

They already fixed it but last relase is two weeks old, I’m assuming the fix is comming with the next release.

As a workaround you could downgrade python-prometheus_client to version 0.23.1-2.

When the error occurs, select Open subshell and do:

python3 -m pip uninstall prometheus_client -y
python3 -m pip install prometheus_client==0.23.1
exit

And then select Retry

5

Thx for your reply. Good to hear that there is a fix already.

What exactly do I have to do if I want to downgrade the python-prometheus_client to version 0.23.1-2?