[nova][placement] Openstack only building one VM per machine in cluster, then runs out of resources

Eugen Block eblock at nde.ag
Mon Jan 31 12:20:31 UTC 2022

Hi all,

I would like to follow up on a discussion from last year [1] since the  
issue is still present.
In a fresh Victoria deployment we faced the same issue and my  
colleague tracked it down to a reoccuring issue within MariaDB [2].  
Quoting from his response to a different thread [3]:

MariaDB is version 10.6.5.
When running placement API in debug mode, its log reveals a message like

"Over capacity for VCPU on resource provider . Needed: 1, Used: 4118,  
Capacity: 768.0"

but checking the entries in the placement db / allocations table shows  
that "4118" is the sum of all resources for the resource provided, not  
only for the CPU class.

The problem results from errors in the DBMS handling the "outer join"  
with a subquery while retrieving the currently allocated resources.

We found a workaround for this environment, but I wanted to bring some  
more attention to this, hoping that this will be fixed in MariaDB.


[2] https://jira.mariadb.org/browse/MDEV-25714

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