Public bug reported:
Today the nova-compute service does not limit the number of concurrent
evacuation requests. The [compute]max_concurrent_build config only
considered for new VM builds but not for re-builds due to incoming
evacuation.
If the evacuated VMs are on shared storage then there is no heavy IO
operations (no image download / convert) then the
[compute]max_concurrent_disk_ops config could not prevent the overload
either.
At some point nova-compute will start failing to process incoming vif-
plugged events in a timely manner. (In a specific env it happened after
more than 60 concurrent evacuation requests targeting the same node)
The [compute]max_concurrent_build config description does not explicitly
states that it is only counts new build requests and ignores rebuilds.
So I consider it a bug in nova-compute that it is not limiting all the
builds by that config option. As this config option is defaulted to 10
it shows that nova never planned to really support significantly more
than 10 concurrent so failing at 60 concurrent evacuation does not need
t be supported.
** Affects: nova
Importance: Undecided
Status: New
** Tags: compute evacuate
** Tags added: evacuate
** Tags added: compute
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https://bugs.launchpad.net/bugs/2083246
Title:
nova-compute can be overloaded with incoming evacuations
Status in OpenStack Compute (nova):
New
Bug description:
Today the nova-compute service does not limit the number of concurrent
evacuation requests. The [compute]max_concurrent_build config only
considered for new VM builds but not for re-builds due to incoming
evacuation.
If the evacuated VMs are on shared storage then there is no heavy IO
operations (no image download / convert) then the
[compute]max_concurrent_disk_ops config could not prevent the overload
either.
At some point nova-compute will start failing to process incoming vif-
plugged events in a timely manner. (In a specific env it happened
after more than 60 concurrent evacuation requests targeting the same
node)
The [compute]max_concurrent_build config description does not
explicitly states that it is only counts new build requests and
ignores rebuilds. So I consider it a bug in nova-compute that it is
not limiting all the builds by that config option. As this config
option is defaulted to 10 it shows that nova never planned to really
support significantly more than 10 concurrent so failing at 60
concurrent evacuation does not need t be supported.
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https://bugs.launchpad.net/nova/+bug/2083246/+subscriptions
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