Open Stack

My understanding is it is still safeish to use when you deal with it right. it causes a transaction abort if the race condition ever hits, and you can keep retrying until your commit makes it. So, there are two issues here:
1. its a more rare kind of abort, so unless you are testing and retrying, it can cause operations to fail in a way the user might notice needlessly. This is bad. It should be tested for in the gate.
2. in highly contended systems, it can be a performance issue. This is less bad then #1. For certain codes, it may never be a problem.

Thanks,
Kevin
________________________________________
From: Zane Bitter [zbitter at redhat.com]
Sent: Thursday, October 11, 2018 10:08 AM
To: openstack-dev at lists.openstack.org
Subject: Re: [openstack-dev] [kolla][tc] add service discovery, proxysql, vault, fabio and FQDN endpoints

On 10/10/18 1:35 PM, Jay Pipes wrote:
> +tc topic
>
> On 10/10/2018 11:49 AM, Fox, Kevin M wrote:
>> Sorry. Couldn't quite think of the name. I was meaning, openstack
>> project tags.
>
> I think having a tag that indicates the project is no longer using
> SELECT FOR UPDATE (and thus is safe to use multi-writer Galera) is an
> excellent idea, Kevin. ++

I would support such a tag, especially if it came with detailed
instructions on how to audit your code to make sure you are not doing
this with sqlalchemy. (Bonus points for a flake8 plugin that can be
enabled in the gate.)

(One question for clarification: is this actually _required_ to use
multi-writer Galera? My previous recollection was that it was possible,
but inefficient, to use SELECT FOR UPDATE safely as long as you wrote a
lot of boilerplate to restart the transaction if it failed.)

> -jay
>
>> ________________________________________
>> From: Jay Pipes [jaypipes at gmail.com]
>> Sent: Tuesday, October 09, 2018 12:22 PM
>> To: openstack-dev at lists.openstack.org
>> Subject: Re: [openstack-dev] [kolla] add service discovery, proxysql,
>> vault, fabio and FQDN endpoints
>>
>> On 10/09/2018 03:10 PM, Fox, Kevin M wrote:
>>> Oh, this does raise an interesting question... Should such
>>> information be reported by the projects up to users through labels?
>>> Something like, "percona_multimaster=safe" Its really difficult for
>>> folks to know which projects can and can not be used that way currently.
>>
>> Are you referring to k8s labels/selectors? or are you referring to
>> project tags (you know, part of that whole Big Tent thing...)?
>>
>> -jay
>>
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