MPM a2dismod/a2enmod failure on config-changed

[Gareth Woolridge]

The latest charm revision published to ch:ubuntu-mirror seems to have a bug when setting the MPM module:

2023-07-17 11:32:13 INFO unit.ubuntu-mirror/1.juju-log server.go:316 CHARM: Configuring mpm
2023-07-17 11:32:13 INFO unit.ubuntu-mirror/1.juju-log server.go:316 CHARM: Switching MPM modules from mpm_b'event' to mpm_worker
2023-07-17 11:32:13 INFO unit.ubuntu-mirror/1.juju-log server.go:316 CHARM: Calling '/usr/sbin/a2dismod mpm_b'event''
2023-07-17 11:32:13 WARNING unit.ubuntu-mirror/1.config-changed logger.go:60 ERROR: Module mpm_bevent does not exist!
2023-07-17 11:32:13 INFO unit.ubuntu-mirror/1.juju-log server.go:316 CHARM: '/usr/sbin/a2dismod mpm_b'event'' failed. Error: Command '['/usr/sbin/a2dismod', "mpm_b'event'"]' returned non-zero exit status 1.
2023-07-17 11:32:13 INFO unit.ubuntu-mirror/1.juju-log server.go:316 CHARM: Calling '/usr/sbin/a2enmod mpm_worker'
2023-07-17 11:32:13 WARNING unit.ubuntu-mirror/1.config-changed logger.go:60 ERROR: Module mpm_event is enabled - cannot proceed due to conflicts. It needs to be disabled first!
2023-07-17 11:32:13 INFO unit.ubuntu-mirror/1.juju-log server.go:316 CHARM: '/usr/sbin/a2enmod mpm_worker' failed. Error: Command '['/usr/sbin/a2enmod', 'mpm_worker']' returned non-zero exit status 1.
2023-07-17 11:32:13 INFO unit.ubuntu-mirror/1.juju-log server.go:316 CHARM: Installed template apache-mpm.tmpl to /etc/apache2/mods-available/mpm_worker.conf

eg: "Switching MPM modules from mpm_b'event' to mpm_worker" seems to point to a bug in the recent py2 to py3 conversion, likely just requiring a .decode()??

The outcome of this bug is that the charm configures mpm_worker in terms of writing config options for apache tuning to disk, but the live apache server is running mpm_event on defaults.

Note it is desirable to switch back to mpm_event anyway (see https://bugs.launchpad.net/ubuntu-mirror-charm/+bug/1868504) but as the MPM module ideally would be configurable this is still a bug.

[Tom Haddon (mthaddon)]

This is fixed in revision 4, which has been published to stable