request to switch to binary build charm

[Edward Hope-Morley]

This charm is built as a source charm and as a result, upgrading the charm results in its wheelhouse being rebuilt on each unit. This typically takes several minutes and on slower systems I have seen it take up to 30 minutes. We recently landed the following guide on how to upgrade ovn from 20.03 to 22.03 and as part of that procedure we upgrade the charm from 20.03/stable to 22.03/stable. Having to wait several minutes for the install to complete before hooks can execute increases the likelihood that things will go wrong for example of a config previously changed has introduced undesired behaviour it would not be possible to revert that change until the build had completed. A binary build charm would remove this build phase and therefore speed up the time to upgrade.

Also worth noting that while the charm is in this upgrade build phase, the logs show no activity if they are at the default INFO level so all you see is the unit status as "executing". To view build progress you can do the following: juju model-config logging-config="<root>=DEBUG"

https://docs.openstack.org/charm-guide/latest/project/procedures/ovn-upgrade-2203.html