Open Stack

Alexei, awesome work.

> Rollbacks are caused not by retry logic but by create_or_update logic:
> We first try to do INSERT in sub-transaction when it fails we rollback 
> this transaction and do update instead.

if you take a look at my patch addressing deadlocks(
https://review.openstack.org/#/c/80461/), i actually added a check to get 
rid of the blind insert logic we had so that should lower the number of 
rollbacks (except for race conditions, which is what the function was 
designed for). i did some minor performance testing as well and will add a 
few notes to the patch where performance can be improved but requires a 
larger schema change.  Jay, please take a look there as well if you have 
time.

> Tomorrow we'll do the same tests with PostgreSQL and MongoDB to see if 
> there is any difference.

i look forward to these results, from my quick testing with Mongo, we get 
about 10x the write speed vs mysql.

> >>>>> We required a non mongo backend to graduate ceilometer. So I don't 
think
> >>>>> it's too much to ask that it actually works.

i don't think sql is the recommended back in real deployments but that 
said, given the modest load of tempest tests, i would expect our sql 
backend be able to handle it.

cheers,
gordon chung
openstack, ibm software standards
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