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#openstack-nova - 2018-03-27
18:47:51 sean-k-mooney[m] cfriesen: uh why. im sure there is a reason but thats wrong
18:47:58 efried cdent: Maybe a ML post would be more expeditious.
18:48:12 sean-k-mooney[m] cfriesen: but for resize we go via the scheduler so we cant assume we will
18:48:18 cdent I think email would be an easier starting point perhaps?
18:48:39 efried ight
18:49:02 sean-k-mooney[m] cfriesen: yes it does but we should not be hard rebooting when we resize or power on a vm
18:49:04 cfriesen sean-k-mooney[m]: hmm, does the fact that we undefine and then define a new domain affect the need to plug the vifs again?
18:49:57 sean-k-mooney[m] cfriesen: actully so again for linux bridge we would need to plug again
18:50:12 sean-k-mooney[m] when qemu exits the tap would be removed form the kernel and the linux bridge
18:50:22 cfriesen sean-k-mooney[m]: from the code comments: "We use _hard_reboot here to ensure that all backing files, network, and block device connections, etc. are established and available before we attempt to start the instance."
18:50:44 cfriesen sean-k-mooney[m]: okay, that explains it then
18:50:44 sean-k-mooney[m] so when we power on we have to add it back
18:50:49 sean-k-mooney[m] for ovs this is persited in the db and not needed
18:51:13 cfriesen sean-k-mooney[m]: persisted over a compute node reboot?
18:51:31 sean-k-mooney[m] cfriesen: is this causeing a bug for you or jsut interested in why its working this way?
18:51:59 cfriesen sean-k-mooney[m]: we're having performance issues and races on compute node startup in a small edge node.
18:52:10 cfriesen sean-k-mooney[m]: trying to figure out what my options are
18:52:12 sean-k-mooney[m] cfriesen: ya the port is stored in the ovs db so when the tap shows up the revalidator treads in the ovs-vswitchd will detect it and add it
18:52:43 openstackgerrit Merged openstack/nova-specs master: Amend volume multi-attach spec https://review.openstack.org/544152
18:53:06 sean-k-mooney[m] cfriesen: i assume you have configured nova to start all instance on server reboot
18:53:50 cfriesen sean-k-mooney[m]: nope, there's another component that's in charge of that. but nova will plug all the vifs on nova-compute startup even if the instances are powered off.
18:54:48 cfriesen that slows down neutron, which causes it to be delayed responding to something else, which times out and does exponential backoff...and the end result is that one or two instance take a long time to become pingable
18:55:26 sean-k-mooney[m] cfriesen: ah ok. i still think its a bug that nova plugs the vifs on compute agent start up. we should proably revisiti if its really needed. as you said we unconditionally plug the vifs when starting a vm so not sure what edge case still requires it
18:56:31 sean-k-mooney[m] the current bevior dates back from nova-networks with linuxbridge but we do several things differently now
18:57:59 cfriesen sean-k-mooney[m]: if we did get rid of the vif plugging at startup, would we have to wait for the network events in _create_domain_and_network() when powering on?
18:58:48 sean-k-mooney[m] cfriesen: we cant wait because only ovs with the neutron agents sends those events correctly
18:59:52 sean-k-mooney[m] cfriesen: linux bridge does not send them reliably and odl only send them when the port is first bound not when port are plugged
19:00:28 cfriesen sean-k-mooney[m]: we do wait on instance spawn though, is that different?
19:01:24 sean-k-mooney[m] cfriesen: we have no ideay what happens for all the rest of the backend but that is why we dont wiat currently
19:02:12 cfriesen sean-k-mooney[m]: kay, thanks for the info.
19:02:37 sean-k-mooney[m] on instance spawn you meen on first boot. and yes that would be different as all backend send a vif plugged event in that case
19:03:21 sean-k-mooney[m] cfriesen: by the way its oke for us to wait for os-vif to plug the vif we just cant wait for neutron to say its wired up. we would like to but all the ml2 dirvers do different things
19:03:25 mlavalle thanks gibi :-)
19:15:24 openstackgerrit Matt Riedemann proposed openstack/nova-specs master: Non-unique network names in Servers IPs API response https://review.openstack.org/521392
19:16:14 mriedem sean-k-mooney[m]: that reminds me, you know how for the new port binding live migration spec we talked about adding a wait on the source host for the vifs to be plugged on the dest host during pre_live_migration?
19:16:25 mriedem i think that is likely not possible now because of ODL
19:16:39 mriedem since ODL won't send a vif plugged event until the port binding changes, right?
19:16:43 mriedem which currently happens in post live migration
19:17:19 sean-k-mooney[m] mriedem: yes didnt you already remove that in your code. we were talking about this last week i think?
19:17:22 mriedem i'm almost inclined to add a [workarounds] config option to disable that wait for vif plugged, but enable the wait by default
19:17:28 mriedem it's a todo in the code right now
19:17:40 mriedem so for ovs and LB we'd default to wait,
19:17:46 mriedem but if you're using ODL, you disable the wait
19:18:57 sean-k-mooney[m] ya odl wont send the event until there is a neutron port update which will only happen when we activate the new building as a result of the change to the host-id in the vif binding_details dicts
19:19:06 sean-k-mooney[m] mriedem: we cant tell if its odl or ovs from nova so we cant wait
19:19:21 sean-k-mooney[m] we can wait for the compute to tell use it has plugged the interface we just cant wait for neutron to say its wired it up
19:19:23 mriedem sean-k-mooney[m]: i know we can't
19:19:28 mriedem but the operator can
19:20:00 mriedem so for live migration, we can default to wait, assuming you're using a networking backend that doesn't suck
19:20:12 mriedem and if you are, then you need to configure nova-compute to not wait for vif plugged events during live migration
19:20:44 mriedem to other specs cores, i think https://review.openstack.org/#/c/521392/ is a no-brainer
19:20:58 sean-k-mooney[m] oh yes we could have a per compute config option or i guess a could wide one for the conductor
19:21:11 mriedem conductor doesn't wait
19:21:12 mriedem compute does
19:21:44 sean-k-mooney[m] mriedem: so in the prelive migrate would we have the dest read the config value and stick it in the migration data
19:22:01 mriedem umm
19:22:09 mriedem i figured the source would read the config since the source host is what's waiting
19:22:21 mriedem if the wait has to depend on the dest, then yeah maybe that has to go into the migrate data object
19:22:31 mriedem if the dest host is using ODL but the source is using OVS
19:23:26 sean-k-mooney[m] well since the dest might have a different network backend to the souce we should get the dest value no?
19:23:37 mriedem probably
19:24:54 sean-k-mooney[m] we proabbly also want to default to not waiting to not break upgrades as that is the default behavior today
19:24:59 sean-k-mooney[m] we can then change the default after 1 release
19:25:20 mriedem oh i suppose
19:25:44 sean-k-mooney[m] or put somthing in the neutorn port binding so neutron can tell use if we should wait or not in the future
19:25:46 mriedem older dest computes wouldn't send the value anyway
19:26:10 mriedem neutron telling us if waiting is safe would be great, but i'm not driving that on the neutron side
19:27:00 sean-k-mooney[m] well the sepc said we would only use the new flow if they both supported it but ya old dest would not send it so its safer to assume dont wait
19:28:01 sean-k-mooney[m] mriedem: honestly i dont think that would be too hard to enable in neutron. i dont know if i have time to look at it but it should be a minor enough api extention
19:28:20 mriedem i mention the old dest compute thing because we had also talked about doing this separately from the blueprint as a bug fix so we could backport it
19:28:28 mriedem but if it requires changes to the versioned object, we can't really backport it
19:28:45 mriedem that was also before we knew that ODL didn't send events
19:29:01 sean-k-mooney[m] basicaly i think we could have a singel key in the portbining dict. vif_plugged_event_policy that could be never,on_bind or on_plug then just hard code it for each of the ml2 drivers
19:30:03 sean-k-mooney[m] mriedem: ah ya that makes sense
19:32:24 sean-k-mooney[m] mriedem: do you want me to open an rfe but for the event stuff and we can see what the neutron team says? it would not be a hard dependecy but it would allow us to know in the future if we can wait
19:33:13 cdent edleafe: responded to your coments on forbidden traits in rp in db. I think you're missing a point or I've explained things very poorly
19:33:57 openstackgerrit Merged openstack/nova-specs master: Non-unique network names in Servers IPs API response https://review.openstack.org/521392
19:34:10 mriedem sean-k-mooney[m]: sure
19:37:57 efried jaypipes, cdent, edleafe: Is there anything preventing two records in the allocations table having the same consumer+rp+rc?
19:39:29 cdent efried: in the table itself, no, but the interface on the object does a full wipe before it does any set (for a given consumer)
19:40:08 efried cdent: duly noted.
19:40:41 mriedem do we have a bp or anything anymore for supporting shared storage pools in nova? there was a bp but i can't find it now, maybe it was marked obsolete?
19:41:08 edleafe cdent: ok, but it seems like overkill. No one would be sending !TRAIT now, so I don't quite get the need to support it
19:41:48 efried mriedem: Since we descoped it in Q, and didn't bring it back up in Dublin...
19:41:57 cdent once that full stack is in place, someone can accidentally use the wrong microversion, and they need an appropriate error
19:42:18 mriedem efried: yeah i'm trying to list it as an alternative in https://review.openstack.org/#/c/551927/
19:42:38 cdent efried, mriedem: tetsuro is still dilligently trying to make shared, correct, yes?
19:43:18 efried mriedem: IIRC, the shared storage provider spec was approved even before Q as one of those vague "we're headed in this direction" things, which led to the inception of aggregates and MISC_SHARES_VIA_AGGREGATE trait, but was never fully tied off.
19:43:32 efried mriedem: And after that we never (re)proposed anything on it.
19:45:26 cdent edleafe: did you see [t 18ze]?
19:45:26 purplerbot <cdent> once that full stack is in place, someone can accidentally use the wrong microversion, and they need an appropriate error [2018-03-27 19:41:56.981348] [n 18ze]
19:45:53 cdent edleafe: because I don't understand why you think it is unnecessary, and would like to
19:46:22 mriedem efried: ok, replied in https://review.openstack.org/#/c/551927/
19:46:28 mriedem dansmith: jaypipes: ^ you might have other ideas
19:46:42 mriedem it's the age old "how can i support migration w/o globally shared ssh keys"
19:47:41 mriedem if you know a set of computes are in a shared storage pool, you could do the shared storage aggregate thing and then we could look that up from nova-compute rather than do the ssh check
19:47:43 efried mriedem: I think this is the closest we came to a shared storage pool spec https://specs.openstack.org/openstack/nova-specs/specs/newton/implemented/generic-resource-pools.html
19:48:28 mriedem before that, we had https://specs.openstack.org/openstack/nova-specs/specs/mitaka/approved/migrate-libvirt-volumes.html
19:48:42 openstackgerrit Merged openstack/nova master: api-ref: Parameter verification for servers.inc (1/3) https://review.openstack.org/528201
19:49:31 mriedem that got held up on the imagebackend refactor o' doom

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