Public bug reported:
[Impact]
On Ubuntu 26.04 (Python 3.14) the cotyledon-based ceilometer agents
(ceilometer-agent-compute, ceilometer-agent-central, ceilometer-polling,
ceilometer-agent-notification) fail to start their workers:
Exception in thread Thread-1 (_child_supervisor_thread):
...
_pickle.PicklingError: Can't pickle local object
<function _ConfigFileOpt.__init__.<locals>.<lambda> ...>
Python 3.14 changed the default multiprocessing start method on Linux from
'fork' to 'forkserver'. cotyledon's ServiceManager uses
multiprocessing.get_context(), so workers are now started by pickling their
arguments, including the parsed oslo_config.ConfigOpts object. With
oslo.config < 10.6.0 the --config-file option type is an unpicklable local
lambda, so spawning fails and the agent collects/publishes nothing.
[Test Plan]
1. Install ceilometer-agent-compute 2:26.0.0-0ubuntu1 on Ubuntu 26.04.
2. Run:
sudo -u ceilometer /usr/bin/ceilometer-polling --polling-namespaces compute
Observe the PicklingError and that no worker starts.
3. Install the fixed package and repeat; the worker starts and the agent
stays up. journalctl -u ceilometer-agent-compute shows no PicklingError.
[Where problems could occur]
The patch explicitly spawns cotyledon workers with the fork start method,
matching pre-3.14 behaviour. A problem would prevent workers from starting.
The heartbeat multiprocessing.Queue in ceilometer-polling keeps the default
context and was verified to work with the fork-spawned workers.
[Other Info]
Root cause is fixed upstream in oslo.config >= 10.6.0 (picklable ConfigOpts
state snapshots for spawn workers); this patch restores pre-3.14 behaviour
for the released 26.04 package. Equivalent fixes: octavia (LP: #2156391),
nova (LP: #2156932).
** Affects: ceilometer (Ubuntu)
Importance: Undecided
Status: Invalid
** Affects: ceilometer (Ubuntu Resolute)
Importance: Undecided
Status: New
** Affects: ceilometer (Ubuntu Stonking)
Importance: Undecided
Status: Invalid
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https://bugs.launchpad.net/bugs/2167831
Title:
ceilometer agents fail to start on Python 3.14: PicklingError on
_ConfigFileOpt lambda
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