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#openstack-nova - 2021-09-07
16:26:30 gibi #topic Open discussion
16:26:37 gibi nothing on the agenda
16:26:42 gibi mloza: your turn
16:26:52 gibi mloza: do you mean flavor extra_specs?
16:26:59 mloza yup
16:27:17 gibi you have to resize the vm
16:27:20 bauzas embedded flavors can't be changed
16:28:44 bauzas unless you resize, indeed
16:29:54 mloza right now live migrating is failing because the instance doesn't have extra_specs that the flavor has. I cannot afford to the resize since it incurs a downtime
16:30:33 dansmith I don't think that's the reason for a live migration failure, right?
16:31:37 mloza i have host aggregates with metadata
16:31:52 mloza the metadata is associated to the flavors
16:32:10 dansmith I see, so it's the aggregate not the flavor
16:32:23 dansmith force migrate should skip that, no? bauzas ?
16:33:05 bauzas wait, was distracted, sorry
16:33:05 gibi force still runs the scheduler isn't it?
16:33:22 bauzas gibi: that depends on the microversion you ask
16:33:25 gibi true
16:33:38 gibi with old enough microversion you can skip the scheduler
16:33:42 bauzas mloza: which exact command do you run ?
16:33:43 dansmith I was going to say, I thought there was a way.. I mean that's how you break your AZ right? :)
16:34:23 gibi host=<new-host> force=True microversion <= 2.67
16:34:32 mloza openstack server migrate --os-compute-api-version 2.30 --live-migration $id
16:34:49 bauzas with no target ?
16:34:59 mloza yep with no taret
16:35:02 mloza target*
16:35:04 gibi you need < 2.30 and you nee d target
16:35:04 bauzas if so, this goes to the scheduler
16:35:13 bauzas which checks this indeed
16:35:17 gibi https://docs.openstack.org/api-ref/compute/?expanded=live-migrate-server-os-migratelive-action-detail#live-migrate-server-os-migratelive-action
16:35:30 dansmith the scheduler is doing what you asked, in that case.. not sending the host to the aggregate that requires specific specs
16:35:35 sean-k-mooney mloza: if you dont pass a target then it will use the az form the request spec
16:35:37 bauzas gibi: or you can use 2.30 with the explicit force flag
16:35:52 gibi bauzas: yes, or <=2.67 and force=True
16:35:54 bauzas (which was deprecated later)
16:35:59 bauzas that, yes
16:36:35 bauzas I'd say, the contract is granted.
16:36:47 bauzas you're asking to migrate something you shouldn't migrate
16:37:02 bauzas I know this is weird
16:37:34 sean-k-mooney if you for the migration will that bypas the aggreate extra spec affintiy filter
16:37:42 sean-k-mooney i assume that is the one that is blocking the host
16:37:47 sean-k-mooney id did not think it would
16:37:49 bauzas but if all your hosts are within aggregates that set metadata and you have a filter that verifies this, then you explicitly write a contract
16:38:45 sean-k-mooney i guess with force we will just check the host exist and skip everything else with the old microverion?
16:39:05 sean-k-mooney that would leave the vm in a state the future move operation will try to move ti out of the aggreate you moved it into
16:39:32 mloza got it to live migrate after passing a target host
16:40:01 gibi OK, I guess that is solve then
16:40:03 gibi :0
16:40:04 gibi :)
16:40:17 gibi any other topic for today?
16:42:10 gibi then lets closed this
16:42:17 gibi thanks for joining
16:42:23 gibi #endmeeting
16:42:23 opendevmeet Meeting ended Tue Sep 7 16:42:23 2021 UTC. Information about MeetBot at http://wiki.debian.org/MeetBot . (v 0.1.4)
16:42:23 opendevmeet Minutes: https://meetings.opendev.org/meetings/nova/2021/nova.2021-09-07-16.00.html
16:42:23 opendevmeet Minutes (text): https://meetings.opendev.org/meetings/nova/2021/nova.2021-09-07-16.00.txt
16:42:23 opendevmeet Log: https://meetings.opendev.org/meetings/nova/2021/nova.2021-09-07-16.00.log.html
16:42:59 bauzas holy shit, I was already knowing about it
16:44:35 mloza Thanks. I think the instance should have extra_specs and prefer live migrating without a target host. If I have to add to extra_specs in the instance, is it instance_extra table that I have to modify ?
16:45:03 mloza instance_uuid='a65b26f5-a278-4200-a573-84e01c685699'; which has "extra_specs": {"aggregate_instance_extra_specs:cephcomputestorage": "true"}
16:45:12 mloza https://paste.opendev.org/raw/bMf35OK3I9aYbCNCv9jm/
16:45:59 gibi mloza: yepp if you want to hack the db then that is the place
16:47:04 sean-k-mooney well there are 2 palces
16:47:20 sean-k-mooney the instance extra table is what woud be used for generating the vm xml and on the compute node
16:47:56 opendevreview melanie witt proposed openstack/placement master: Narrow scope of set allocations database transaction https://review.opendev.org/c/openstack/placement/+/807014
16:48:58 sean-k-mooney i woudl hope that is the same falvor we use for move operation inthat are not resize but we do also have flavor info in the request spec which is what is passed to the schduler filters
16:49:32 sean-k-mooney the schduler never uses the info in the instance_extra tabel driectly
16:51:18 mloza where does the scheduler pull info if not from instance_extra table ?
16:52:01 sean-k-mooney i belive we invoke the schduler with a populated request spec object when we do the select destioantion call form the conductor
16:52:16 sean-k-mooney but technially there is a request_sepcs table in the api db
16:52:23 sean-k-mooney with a serialised copy of the requst spec
16:53:15 bauzas sean-k-mooney: this is correct
16:53:25 bauzas but when you resize (eg.) you update the request spec
16:53:33 sean-k-mooney yes
16:53:37 bauzas for the flavor, I mean
16:53:40 sean-k-mooney but what about live migrate and cold migrate
16:53:48 sean-k-mooney do they just use the api db copy
16:54:03 sean-k-mooney or reconstruct it form the embeded flavor in the cell db
16:54:37 bauzas cold and live migrate don't modify the resources, right?
16:54:48 bauzas resize and rebuild do
16:55:08 bauzas so, yes, we just call out the request spec from the api table
16:55:23 bauzas we never lookup the cell db
16:55:37 sean-k-mooney right which has an enbeded copy of the flavor extra specs
16:55:49 bauzas the instance table, you mean?
16:56:06 sean-k-mooney mloza: so you would have to update both the instnace_extra table for the compute node to use and request_specs table for the scuduler to use
16:56:28 sean-k-mooney bauzas: no the request_spec has a full embeded copy of the flavor as a json blob
16:56:40 sean-k-mooney well seriasised nova object
16:56:42 bauzas ah this
16:56:46 bauzas yes
16:57:03 bauzas we have the embedded flavor stored in two places
16:57:03 sean-k-mooney so if mloza is changing it to make live migrateion work they need to update the request_sepc version
16:57:09 sean-k-mooney bauzas: yes
16:57:16 bauzas one in the api db within the request_specs table
16:57:26 bauzas one in the cell db within the instances table
16:57:40 bauzas the instances table is never used for scheduling decisions
16:57:42 sean-k-mooney instance_extra but yes
16:57:49 bauzas my bad, yes indeed
16:58:08 mloza i looked at request_specs in nova api db and indeed, there is extra_specs
16:58:11 sean-k-mooney so mloza you would have to keep both in sync if you do decide to hack the db
16:59:56 mloza noted. thanks for the info

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