| Posted | Nick | Remark | |
|---|---|---|---|
| #openstack-nova - 2025-12-11 | |||
| 15:58:48 | noonedeadpunk | I was thinking if that could solve trade-offs with upcalls | |
| 15:59:00 | sean-k-mooney | no it does not help | |
| 16:00:01 | noonedeadpunk | yeah, so each cell has own db and mq, where main load is handled, but then all conductors would connect to this db, which might be an option if you have like couple of cells | |
| 16:00:16 | sean-k-mooney | this was one fo the things tripleo got very wrong when they first added the ablity to add an addtional cell | |
| 16:00:34 | noonedeadpunk | okay, gotcha | |
| 16:06:49 | noonedeadpunk | I guess next part is - how that is working with AZs.... | |
| 16:07:07 | sean-k-mooney | compeltely unerlated concepts | |
| 16:07:39 | noonedeadpunk | but like... it would make sense to have cell per az? | |
| 16:07:52 | sean-k-mooney | hosts in a cell can be in diffent AZs and AZ can refence hosts in multiple cells | |
| 16:08:22 | sean-k-mooney | noonedeadpunk: that is one apprch but it depend on your usecase | |
| 16:08:32 | sean-k-mooney | its not forced in anyway | |
| 16:08:50 | noonedeadpunk | as given AZ is geographically spread, having mariadb/rabbitmq cluster isolated in it - makes sense | |
| 16:09:18 | sean-k-mooney | AZ in openstack have many uses that is only one of them | |
| 16:09:28 | noonedeadpunk | oh right, sure | |
| 16:09:47 | sean-k-mooney | remember that AWS aviablity zone are a better logical map to a keystone region then they are to a nova AZ | |
| 16:10:33 | noonedeadpunk | right, though what we are trying to do, is to have stretched tenant networks between AZs | |
| 16:10:54 | sean-k-mooney | again cells are for scaling. if you scaling unit happend to be a dataceneter and each datacenter is phsycial spreand then 1 cell per datacenter and one AZ per data ceneter might make sense | |
| 16:10:57 | noonedeadpunk | and have workloads stretched as well, which you can not do easily with different regions | |
| 16:11:10 | noonedeadpunk | yup | |
| 16:11:35 | sean-k-mooney | well tenant network are intended to be aviable across all AZ and cells so unless you using l3 routed networks that the default | |
| 16:11:36 | noonedeadpunk | I just bet there are plenty scheduling complications on top.... | |
| 16:11:53 | noonedeadpunk | right, which is not the case with keystone regions | |
| 16:11:53 | sean-k-mooney | also there is no cell concep on the neutron side so its 1 neutron for all cells by default | |
| 16:18:46 | tkajinam | stephenfin, do you mind voting +A when you have time ? https://review.opendev.org/c/openstack/nova/+/943083 +A was postponed due to feature freeze period of 2025.2 but the freeze was lifted, apparently | |
| 16:19:04 | tkajinam | sean-k-mooney, or if you have time | |
| 16:23:32 | opendevreview | Takashi Kajinami proposed openstack/nova master: Replace remaining reference to policy.json https://review.opendev.org/c/openstack/nova/+/970648 | |
| 16:38:20 | noonedeadpunk | I also assume that for multi-cell environment, you pretty much never want to use template urls, as I'd guess it will make super conductor extremely confused? | |
| 16:39:10 | noonedeadpunk | or force to use the same password for all cells? | |
| 16:43:04 | sean-k-mooney | yes either works. | |
| 16:44:14 | sean-k-mooney | template urls were built for tripleo ot remvoe password form the db but we intentionally do not use them in our new installer and revert to non templeted urls to simplicy mangement of them over time | |
| 16:44:31 | sean-k-mooney | they are useful in theory but less so in practice | |
| 16:46:30 | noonedeadpunk | we have adapted them quite some time ago as well, because of some bug in nova-manage - when a command with different password was just creating another cell. So it was breaking nova on password rotation process | |
| 16:46:41 | noonedeadpunk | (I bet I reported it) | |
| 16:47:34 | noonedeadpunk | as then you also need to properly time update of the cell with service restart.... | |
| 16:49:00 | noonedeadpunk | https://bugs.launchpad.net/nova/+bug/1923899 | |
| 16:49:17 | noonedeadpunk | it's still in review :D | |
| 16:49:44 | sean-k-mooney | you should not return the create cell command | |
| 16:49:55 | sean-k-mooney | that is not for updating the cell | |
| 16:50:03 | sean-k-mooney | it sfor creating a new one | |
| 16:50:37 | sean-k-mooney | if you want ot update use the update command https://docs.openstack.org/nova/latest/cli/nova-manage.html#cell-v2-update-cell | |
| 16:51:01 | sean-k-mooney | the name is for human uses only its not the uniuqe identifyer | |
| 16:52:10 | sean-k-mooney | this is somewhere between user error and a missign unique constratit | |
| 16:52:33 | sean-k-mooney | interally nova only uses the cell uuid for joins | |
| 16:52:59 | noonedeadpunk | I Guess it's kidna general expectation of name_or_uuid behavior as well... | |
| 16:53:16 | sean-k-mooney | right that not the documented behavior | |
| 16:53:24 | sean-k-mooney | and we dont support that for nova-mange normally | |
| 16:53:29 | noonedeadpunk | as it's kinda hard in automated tooling to reference by uuid, but yeah, I get the point | |
| 16:53:30 | sean-k-mooney | that a openstack client thing | |
| 16:53:48 | sean-k-mooney | not somethng that the api or project -manage command typeicly support | |
| 16:54:44 | sean-k-mooney | the propsed path is not actully a fix | |
| 16:54:58 | sean-k-mooney | its a nova status commadn to detech cells with the same name | |
| 16:55:19 | sean-k-mooney | it does tno prevnet it from happeign or actully adress te bug | |
| 16:55:40 | sean-k-mooney | well there are two https://review.opendev.org/c/openstack/nova/+/901810 | |
| 16:55:49 | sean-k-mooney | is the nova-status check | |
| 16:56:39 | noonedeadpunk | it could be helpful as well, but yeah... | |
| 16:56:40 | sean-k-mooney | https://review.opendev.org/c/openstack/nova/+/876940 changed the unique constrating but that has upgrade impacts | |
| 16:59:16 | noonedeadpunk | how the heck notifications are even supposed to work in multi-cell envs.... | |
| 16:59:52 | noonedeadpunk | or well. you set yet another rabbitmq cluster for notifications ,and all services can report to it.... | |
| 16:59:57 | noonedeadpunk | I guess that's the way.... | |
| 17:00:08 | sean-k-mooney | well you are recommened to use a dedicated rabbit for notrication regardless of cells | |
| 17:00:52 | sean-k-mooney | so it does not really change that you eithe ruse one rabbit for noticaion for all cells or you need to have 1 per cell and listnet to muptle notificions busses in yoru applcations | |
| 17:01:00 | noonedeadpunk | and then they are not scaled with cells, simple as that I guerss | |
| 17:01:22 | noonedeadpunk | oh, right... or that | |
| 17:01:26 | sean-k-mooney | it depend i belive celipmenter supprots a list of notificaon transport urls | |
| 17:01:48 | sean-k-mooney | but its more commont to just use 1 dedicated rabbit for them | |
| 17:02:46 | sean-k-mooney | but again that not really difent then a normal deployment where the recommadnation has alwasy beend seperate rpc and notficaiton traffic to diffent rabbit instances | |
| 17:03:58 | noonedeadpunk | yes, true, I was just thinking of implications of cells, like firewalling, etc, where ceilometer should be also allowed to get connected to these cell-specific notification clusters or whatever... | |
| 17:04:30 | noonedeadpunk | it somehow feels to have an enomorous amount of various implications for deployments | |
| 17:21:40 | sean-k-mooney | no more so then condotor groups or shard in ironic | |
| 17:21:54 | sean-k-mooney | but cells are an architecural choice | |
| 17:22:44 | sean-k-mooney | cells are very diffent then AZs AZ are just names on an aggrete | |
| 17:23:19 | sean-k-mooney | cells is about how you architect yoru clodu to scale and deserves the same tought like l3 routed netowrk for neutron | |
| 17:30:14 | melwitt | sean-k-mooney: I don't think those are duplicates fwiw. https://bugs.launchpad.net/nova/+bug/2132020 is debatable as a bug bc instances in ERROR state do still consume resources (from a quota perspective) until they are deleted. I don't have a 100% opinion on that without thinking about it more | |
| 17:31:40 | noonedeadpunk | I am jsut frankly concerned that by the time when you might get up to a limit of rabbitmq/mariadb for nova, you will have a more bottleneck at other place | |
| 17:31:53 | noonedeadpunk | (like neutron db) | |
| 17:33:22 | JayF | I mean, yeah. Ironic has been dealing with problems shaped like that for years, with Nova computes being the thing we outscale | |
| 17:33:29 | JayF | and we figured it out (shards and conductor groups) | |
| 17:35:35 | noonedeadpunk | and cell_mappings in nova_api is pretty much used only by superconductor, right? So when cell mapping is not templated, but you need to update password, you pretty much caring about config change and restart of superconductor with cell mapping change? | |
| 17:39:10 | noonedeadpunk | and it feels like with rabbitmq quorum queues and using streams for fanouts, rabbit become more horizontally scalable then it used to be... but yeah... | |
| 17:43:12 | sean-k-mooney | melwitt: they are not entirly but i think they are related | |
| 17:44:12 | sean-k-mooney | melwitt: https://bugs.launchpad.net/nova/+bug/2132020 depend o nthe way the error happened. | |
| 17:44:29 | sean-k-mooney | basiclly if we have berried the isntance in cell 0 because of a no valid host | |
| 17:44:58 | sean-k-mooney | then we shoudl free any placment allcation on comptue nodes for it | |
| 17:45:08 | sean-k-mooney | the same way we do when you shelve offload | |
| 17:45:24 | sean-k-mooney | if the isntance is in error but insthace.host is pointing at a real host | |
| 17:45:28 | sean-k-mooney | then we need to keep the allcation | |
| 17:45:28 | melwitt | I'm saying it's not 100% clear whether that's consistent bc currently any instance that has an instance record consumes quota | |
| 17:45:38 | sean-k-mooney | because in thiory you coudl rebuild ro hard reboot the vm | |
| 17:46:03 | sean-k-mooney | we do the instnace count check sepreaty form the palcmenet allcation | |
| 17:46:26 | sean-k-mooney | i think the orgianll assution is the qutota violation is not for the instnace quota | |
| 17:48:40 | melwitt | yeah, I dunno. it is just not 100% clear to me what to do to make sure things are consistent | |
| 17:49:39 | sean-k-mooney | i dont know if you have had time to look at the regression test https://review.opendev.org/c/openstack/nova/+/969251 | |
| 17:49:52 | sean-k-mooney | im still trying to figure out if it is valid base don that for waht its worht | |
| 17:50:13 | sean-k-mooney | the two just seam realted to me and i wanted to make sure we were not tryint to solve the same thing in two diffent ways | |
| 17:50:45 | melwitt | no I only skimmed | |
| 17:51:09 | sean-k-mooney | the repoducer has not conviced me its an actula bug yet for what its worth | |
| 17:53:06 | sean-k-mooney | it looks like they actully might be using the logic form https://opendev.org/openstack/nova/src/branch/master/nova/tests/functional/regressions/test_bug_1806064.py#L92 | |
| 17:53:19 | sean-k-mooney | to simulate this so maybe it is the num isntance quota | |
| 17:53:45 | sean-k-mooney | to me if we exceed quota but are not shcduled to a host as a restl of it we shoudl not eb preventign other instances form using that space | |
| 17:54:04 | sean-k-mooney | but we obviously cant delete the allcaiton if there si any change of htis vm being recovered | |