Re: [libvirt] [PATCH 3/5] network: read status from old location and move to new

On 04/15/2014 03:27 PM, John Ferlan wrote: > > On 04/10/2014 09:19 AM, Laine Stump wrote: >> This eliminates problems with upgrading from older libvirt that stores >> network status in /var/lib/libvirt/network to newer libvirt that >> stores it in /var/run/libvirt/network, by also reading any status >> files from the old location, saving them to the new location, and >> removing them from the old location. >> >> This will not help those trying to downgrade, but in practice this >> will only be problematic in two cases >> >> 1) If there are networks with network-wide bandwidth limits configured >> and in use by a guest during a downgrade to "old" libvirt. In this >> case, the class ID's used for that network's tc rules, as well as >> the currently in-use bandwidth "floor" will be forgotten >> >> 2) If someone does this: 1) upgrade, 2) downgrade, 3) modify running >> state of network (e.g. add a static dhcp host, etc), 4) upgrade. In >> this case, the modifications to the running network will be lost >> (but not any persistent changes to the network's config). >> >> I have an idea of how to make these cases work properly as well >> (involving symlinks in /var/lib pointing to /var/run) but want to >> avoid keeping such an ugly legacy around (forever) unlesss others >> think it is absolutely necessary to support flawless downgrades across >> this line *while remaining in service*. > I would have to believe/think the downgrade issue has happened before > with some other change to config or status file locations. Thinking about it, there was one similar situation - when sessionmode libvirtd switched from using gnome2 config directories to gnome3. I don't recall if anything special was done in that case, or if it was just considered not important because ... session mode.