If the hub and web are running on the same host (or rather under the same httpd server), then they can share python processes and affect each other.
I noticed this while debugging #3755. There were duplicate log output lines with different formats. It turns out these are because the hub and web code both add log handlers for the koji logger.
koji
The log behavior is the only problem I see so far. This is a pretty common scenario, so I doubt there's any serious problem here, but it's worth thinking about the risks here and how best to mitigate them.
Both hub and web are designed to be stateless handlers, but if this logging issue can happen, then something else could possibly crop up.
Actually, I believe this was fixed in #2731, but some instances might not have the config update if they manage their own httpd config
Metadata Update from @mikem: - Custom field Size adjusted to None
Metadata Update from @mikem: - Issue close_status updated to: Fixed - Issue status updated to: Closed (was: Open)
This issue has been migrated to Fedora Forge: https://forge.fedoraproject.org/koji/koji/issues/3954
Please continue any further discussion there.