On Wed, Jun 27, 2018 at 10:41:38AM +0200, Markus Armbruster wrote: > Markus Armbruster <arm...@redhat.com> writes: > > > Markus Armbruster <arm...@redhat.com> writes: > > > >> I fooled around a bit, and I think there are a few lose ends. > > [...] > >> Talking to a QMP monitor that supports OOB: > >> > >> $ socat UNIX:test-qmp READLINE,history=$HOME/.qmp_history,prompt='QMP> > >> ' > >> {"QMP": {"version": {"qemu": {"micro": 50, "minor": 12, "major": 2}, > >> "package": "v2.12.0-1703-gb909799463"}, "capabilities": ["oob"]}} > >> QMP> { "execute": "qmp_capabilities", "arguments": { "oob": true } } > >> {"error": {"class": "GenericError", "desc": "Parameter 'oob' is > >> unexpected"}} > >> QMP> { "execute": "qmp_capabilities", "arguments": { "enable": ["oob"] > >> } } > >> {"return": {}} > >> QMP> { "execute": "query-qmp-schema" } > >> {"error": {"class": "GenericError", "desc": "Out-Of-Band capability > >> requires that every command contains an 'id' field"}} > >> > >> Why does every command require 'id'? > > > > I found one reason: event COMMAND_DROPPED wants it. Any other reason? > > > > [...] > > Apropos COMMAND_DROPPED: we send an event rather than an error response > because we may send it out-of-order. Makes sense. > > However, broadcasting it to all monitors doesn't make sense. We could > use a way to send an event to just one monitor.
Worse than that - broadcasting to all monitors is categorically broken. Different monitors make use the same "id" formatting scheme, so if you broadcast COMMAND_DROPPED to a different monitor you might have clashing "id" and thus incorrectly tell a client its command was dropped when in fact it was processed. You'd have to be fairly unlucky in timing, but it could happen. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|