| Posted | Nick | Remark | |
|---|---|---|---|
| #openstack-nova - 2025-07-02 | |||
| 19:39:35 | mikal | Like for example it execs a command line to build the ISO image, solely because the only library we could find at the time to do it nicely was GPL and we refused to use GPL dependencies. | |
| 19:39:37 | fungi | agreed, it has challenges, for example the earlier change at the start of this discussion about using virtio for cdrom devices by default, because debian doesn't include ahci drivers in their genericcloud kernel configs | |
| 19:40:07 | mikal | FAT config drives should work too? IIRC it doesn't _have_ to be a CDROM, it just defaults to that? | |
| 19:40:12 | mikal | Its been a long time. | |
| 19:40:52 | fungi | it probably could be any kind of block device, i think it was virtual cd by convention so not sure if that assumption is baked into places (e.g. in cloud-init) | |
| 19:42:11 | fungi | granted, forcing a different device type is still going to be a custom image property on upload or some similar override, if it's not nova's default | |
| 19:51:47 | mikal | So cloud-init will only probe for a couple of things to match -- device ID matters (config2) and type. The probing code only looks for CDROMs or FAT formatted disks IIRC. | |
| 19:53:10 | mikal | Honestly, most of the people I know who really use metadata use it as a poor man's replacement for Nova not having some sort of mature out of band agent thing. They really want AWS SSM agent or equivalent -- https://docs.aws.amazon.com/systems-manager/latest/userguide/ssm-agent.html. | |
| 19:54:17 | mikal | We could do the same with either a custom agent or the qemu agent (although the qemu agent has some pretty big limitations), that bit isn't too hard. The hard bit is marshalling the requests into the instance. That likely involves some sort of per-instance queue that Nova doesn't have right now. | |
| 19:58:38 | fungi | yeah, an actual communication channel from host to guest at least, if not bi-directional | |
| 19:59:04 | mikal | Yeah, specifically one which doesn't not require networking to be configured and working. | |
| 19:59:38 | mikal | I worked for a training startup for a bit... We did all sorts of contortions to rescue VMs when students messed up their networking. This would have made it so much easier. | |
| 19:59:49 | fungi | a fifo-like proc interface in the kernel or something would be amazing | |
| 20:00:29 | fungi | and/or pseudofiles like device drivers tend to expose | |
| 20:00:32 | mikal | So qemu-agent uses a unix domain socket on the outside and virtio-serial on the inside and speaks JSON blobs, which is a bit terrible. Serial means only one talker at a time. | |
| 20:01:39 | fungi | though at boot time, one talker in the guest is generally sufficient? | |
| 20:01:48 | mikal | ShakenFist does this with a unix domain socket on the outside and virtio-vsock on the inside, and speaks protobufs. That's actually really cool if I don't say so myself because the in-guest agent can just run a socket server like you're used to and serve N requests at the same time because virtio-vsock does all the multiplexing for you. | |
| 20:01:59 | fungi | or maybe not these days, with the advent of parallel boot processing | |
| 20:02:40 | mikal | Serialized requests forces you to come up with some sort of queueing / locking mechanism to handle the case of multiplem requests, even if its not used much. | |
| 20:03:14 | fungi | the protobuf design sounds nice, if only protobuf libraries weren't such shifting sand these days (ut maybe they're getting better) | |
| 20:03:53 | mikal | https://www.madebymikal.com/virtio-vsock-python-examples-of-running-the-server-in-the-guest/ is what I wrote up when I was playing with virtio-vsock. | |
| 20:06:23 | fungi | yeah, i guess low-level socket access like that is probably enough for these cases, you don't need google's own protobuf libs | |
| 20:09:34 | fungi | oh, i see what you're saying, shakenfist tunnels protobufs over an interface like that | |
| 20:09:52 | fungi | you'd still need separate libs for the serialization i guess | |
| 20:12:10 | mikal | Yes, virtio-vsock is the transport, and I talk protobuf down it. Qemu talks JSON in its similar but slightly more terrible case. | |
| 20:12:21 | mikal | Notably I do not talk gRPC, just the serialization protocol. | |
| 20:12:39 | mikal | But meh, its just serialization. It could be JSON for all it matters. | |
| 20:12:59 | mikal | The in-guest agent could present a REST API for example over virtio-vsock and that would not be insane. | |
| 20:15:57 | fungi | makes sense, and yes grpc is a much bigger mess | |
| 20:17:34 | mikal | On reflection, I am also a bit confused about the "tangled python deependencies" answer to why glean is needed compared to cloud-init. Isn't that just a case of using venvs for the various competing components? Especially when modern pythons are super opposed to you installing directly into the system pip? | |
| 20:29:41 | fungi | devstack is finally in a position to be able to isolate openstack services from the system python module search path, but that's an extremely recent change | |
| 20:35:21 | fungi | i recall clarkb hacked on versions of that improvement for years before it reached a state others in the community were comfortable with | |
| 20:36:41 | clarkb | from the CI/OpenDev perspective I think there are two primary reasons we liek config drive. The first is that it is incredibly reliable. The boot error rate with metadata service is >0 and in some cases quite high. The other is that it is simple. Cloud-init configures a lot of stuff and sometimes in desctructive ways (it once decided to do bad things to volume mounts). Glean | |
| 20:36:43 | clarkb | sets up your network and ssh keys and that is about it | |
| 20:37:17 | clarkb | today we can only boot ubuntu noble in rackspace classic with config drive. Metadata does not work. This is with the upstream ubuntu noble cloud image which uses cloud init (not glean) | |
| 20:37:55 | clarkb | (that is because rackspace doesn't do metadata in the way normal clouds do iirc and they don't have their custom image for noble yet (or ever) so the only way it works with standard tools is config drive) | |
| 20:39:09 | clarkb | naively I'm not sure what the issue is. From the end user standpoint config drive is simple and bullet proof | |
| 20:40:26 | clarkb | the ability to mount iso9660 or fat32 devices is near univeral, the data is small and static. Using a complicated api service that requires hosts know how to magically negotiate a protocal more complicated than `mount` is always going to be more error prone. | |
| 20:40:53 | clarkb | iirc there are layers of proxies involved ont he backend too (which I want to say was the assumed source of the flakyness when we shifted all our ci nodes to config drive) | |
| 21:00:54 | mikal | I am not sure there is an issue, I am just surprised given config drive was meant to be a temporary fix which seems to have "rusted on". If it's genuinely around forever it could probably do with some love. | |
| 21:07:30 | clarkb | I think the primary downside to config drive is that it consumes one of your disk slots. I know this is a problem for Xen. Not sure about KVM | |
| 21:08:11 | clarkb | with Xen you only get something like 16 disks. One of which is implicitly owned by the root disk then config drive consumes a second. This limits you to 14 devices which may limit the total storage attachable to the instance if you also have volume size limits | |
| #openstack-nova - 2025-07-03 | |||
| 01:45:58 | sean-k-mooney[m] | i dont think we should supprot the dmi info at all | |
| 01:46:28 | sean-k-mooney[m] | its a libvirt internal implation detail so im really not a fan of building on that for config drive or any other metadata mechanium | |
| 01:47:12 | sean-k-mooney[m] | i certainly dont want to rush into adding supprot for this as a bug fix without propper discussion as this si an undocumjented internal detail | |
| 01:51:04 | sean-k-mooney[m] | if your using virtio-scsi you can have 100s of disks if needed but iconfig drive does consume a pci/pcie sloct by default but iits not generally a problem | |
| 06:43:33 | mikal | sean-k-mooney[m]: I finally have all the USB and sound changes passing CI, so that's nice. | |
| 09:00:03 | Uggla | sean-k-mooney[m], fyi I did a first review pass on 953940: support iothread for nova vms | https://review.opendev.org/c/openstack/nova-specs/+/953940 | |
| 09:25:49 | bauzas | sean-k-mooney[m]: honestly, I'd prefer to leave the current owner to provide a new revision from him | |
| 09:54:34 | mikal | For what its worth, https://review.opendev.org/q/topic:%22libvirt-vdi%22 is a series of four patches all with passing CI and a +2 on them if someone has a spare minute or two. | |
| 10:01:26 | sean-k-mooney | bauzas: well i wanted to hevilaly revise there proposal, also i have propsoed thie in some form twice before so i wrote it form scratch based on my prior exploration of this in past cycles | |
| 10:38:14 | opendevreview | Alexey Stupnikov proposed openstack/nova master: Don't create instance_extra entry for deleted instance https://review.opendev.org/c/openstack/nova/+/412771 | |
| 11:49:18 | opendevreview | Rajesh Tailor proposed openstack/nova-specs master: Show finish_time field in instance action show https://review.opendev.org/c/openstack/nova-specs/+/929780 | |
| 12:10:16 | opendevreview | sean mooney proposed openstack/nova-specs master: support iothread for nova vms https://review.opendev.org/c/openstack/nova-specs/+/953940 | |
| 12:43:01 | opendevreview | Biser Milanov proposed openstack/nova master: Hardcode the use of iothreads for KVM. https://review.opendev.org/c/openstack/nova/+/918669 | |
| 12:43:31 | opendevreview | Biser Milanov proposed openstack/nova master: Hardcode the use of iothreads for KVM. https://review.opendev.org/c/openstack/nova/+/918669 | |
| 12:54:22 | opendevreview | Balazs Gibizer proposed openstack/nova master: Warn on long task wait time for executor https://review.opendev.org/c/openstack/nova/+/952666 | |
| 12:54:22 | opendevreview | Balazs Gibizer proposed openstack/nova master: Run nova-api and -metadata in threaded mode https://review.opendev.org/c/openstack/nova/+/951957 | |
| 12:54:23 | opendevreview | Balazs Gibizer proposed openstack/nova master: Run unit test with threading mode https://review.opendev.org/c/openstack/nova/+/953475 | |
| 12:54:23 | opendevreview | Balazs Gibizer proposed openstack/nova master: Allow to start unit test without eventlet https://review.opendev.org/c/openstack/nova/+/953436 | |
| 12:54:24 | opendevreview | Balazs Gibizer proposed openstack/nova master: [test]RPC using threading or eventlet selectively https://review.opendev.org/c/openstack/nova/+/953815 | |
| 12:59:19 | opendevreview | Balazs Gibizer proposed openstack/nova master: Do not yield in threading mode https://review.opendev.org/c/openstack/nova/+/950994 | |
| 12:59:20 | opendevreview | Balazs Gibizer proposed openstack/nova master: Warn on long task wait time for executor https://review.opendev.org/c/openstack/nova/+/952666 | |
| 12:59:20 | opendevreview | Balazs Gibizer proposed openstack/nova master: Run nova-api and -metadata in threaded mode https://review.opendev.org/c/openstack/nova/+/951957 | |
| 12:59:21 | opendevreview | Balazs Gibizer proposed openstack/nova master: Run unit test with threading mode https://review.opendev.org/c/openstack/nova/+/953475 | |
| 12:59:21 | opendevreview | Balazs Gibizer proposed openstack/nova master: Allow to start unit test without eventlet https://review.opendev.org/c/openstack/nova/+/953436 | |
| 12:59:22 | opendevreview | Balazs Gibizer proposed openstack/nova master: [test]RPC using threading or eventlet selectively https://review.opendev.org/c/openstack/nova/+/953815 | |
| 13:04:32 | sean-k-mooney | bauzas: can you provide input on specifcly this comment https://review.opendev.org/c/openstack/nova-specs/+/953940/comment/c0db3aad_9199e6e7/ do you want me to move hw:iothreads_per_disk to the alternitives or only update the iothread on reboot for this cycle. | |
| 13:04:53 | sean-k-mooney | ill simplfy the spec based on that input. | |
| 13:06:14 | sean-k-mooney | long term we defintly shoudl supprot hw:iothreads_per_disk btu we dont need to supprot it initally my expection is we will enhance the iothrad funciotnaltiy incremnetally over a few rleases as we need too. | |
| 13:08:31 | sean-k-mooney | the ohter thing i was undeceded on was shoudl it be hw:iothreads_per_disk or hw:iothreads_per_volume i.e. the number of addtional io treads to add per cinder volume or per any disk assocated with the guest i.e. swap or ephemreal | |
| 13:09:21 | sean-k-mooney | i think for simplictly to have a baseline this cycle we shoudl just simplfy and move all the per disk part to a diffent spec for next cycle like you were suggesting | |
| 13:15:46 | bauzas | sean-k-mooney: yeah my concern was about to say "given all the discussions we need to have for iothreads per disk, maybe we should just do that by another spec" | |
| 13:16:30 | bauzas | and my main concern with that is the fact that we need to restart an instance for using other io threads if we modify the number when we add a new volume | |
| 13:18:50 | sean-k-mooney | so we dont actuuly need the restart as far as i can tell but we can just update the xml we need to call a sperat api to add or remove the iothread | |
| 13:19:31 | sean-k-mooney | so ok ill move alll fo that to alterniivs and simplfy the spec to only static iothread set via the hw:iothreads extra spec | |
| 13:20:19 | bauzas | oh, the libvirt API accepts a specific call to add a new iothread ? | |
| 13:20:44 | bauzas | if so, tell that please :) | |
| 13:21:13 | sean-k-mooney | so you can do it on the cli to a live domain. i commented on that in my reply | |
| 13:21:29 | sean-k-mooney | so there is an api but i need to go find what virsh is calling | |
| 13:21:47 | sean-k-mooney | but we do need to track/assign the iothread id to use it | |
| 13:22:02 | sean-k-mooney | so we can use it but its more complexity then i would ike to do this cycle | |
| 13:29:10 | sean-k-mooney | im going to simplfy the cpu affintiy too. | |
| 13:51:30 | opendevreview | sean mooney proposed openstack/nova-specs master: support iothread for nova vms https://review.opendev.org/c/openstack/nova-specs/+/953940 | |
| 14:05:50 | opendevreview | Rajesh Tailor proposed openstack/nova-specs master: Show finish_time field in instance action show https://review.opendev.org/c/openstack/nova-specs/+/929780 | |
| 14:30:35 | opendevreview | sean mooney proposed openstack/nova-specs master: support iothread for nova vms https://review.opendev.org/c/openstack/nova-specs/+/953940 | |
| 14:34:33 | opendevreview | sean mooney proposed openstack/nova-specs master: support iothread for nova vms https://review.opendev.org/c/openstack/nova-specs/+/953940 | |
| 14:43:56 | sean-k-mooney | Uggla: bauzas ^ the only open quesiton left in that version is triat or compute service bump. a triat is simpler in my view and will be a better ux but i am not going to update the spec until folks provide feed back. i need to go test somethign else for a bit | |
| 14:51:03 | Uggla | sean-k-mooney, I'm more in favor of trait, but I'm not sure I have rational behind that. I need to think about it. | |
| 14:51:54 | sean-k-mooney | i do it work for mixed clouds with diffent virt drivers | |
| 14:52:13 | sean-k-mooney | either differnt version or vmware + libvirt or libvirt + ironic ectra | |
| 14:52:27 | sean-k-mooney | we can do it th eother way but to me its harder to implement correctly | |
| 16:50:55 | opendevreview | Masahito Muroi proposed openstack/nova-specs master: Add spec for virtio-blk multiqueue extra_spec https://review.opendev.org/c/openstack/nova-specs/+/951636 | |
| 16:55:07 | masahito | Thanks for the quick reviews. I narrow down the spec scope only supporting multiqueue to enable the incremental supports and to simplify the discussion. | |
| 16:58:40 | sean-k-mooney | masahito: im sorry that we didnt really have tiem to work on this mroe closely earlier in the cycle | |
| 16:59:59 | sean-k-mooney | masahito: im not entrily sure what the right thing to do is. technial the approval deadline is end of buisse today | |
| 17:00:46 | sean-k-mooney | ill try and take a look at your spec again shortly | |
| 17:00:55 | sean-k-mooney | btu im not sure if other will have time today | |
| 17:09:56 | masahito | it's ok. I understand the iothreads part needs extra discussion now because of the entire Nova consistency. | |
| 17:11:13 | opendevreview | Merged openstack/nova master: Use futurist for _get_default_green_pool() https://review.opendev.org/c/openstack/nova/+/948072 | |