[Evergreen-dev] Time to deprecate "authoritative" APIs?

[Blake Henderson]

Bill,

That is interesting. I can put in my two cents to say: we do not use a 
database scenario other than the primary/secondary replication scenario. 
Where primary is a single machine and receives updates. The secondary is 
configured in read-only streaming replication. All of the bricks are 
configured to talk to primary IP/hostname. It would seem that this patch 
could bring about a speedup for us with no downside, unless I'm mistaken.

-Blake-
Conducting Magic
Will consume any data format
MOBIUS

On 3/20/2023 3:07 PM, Bill Erickson via Evergreen-dev wrote:
> Hi All,
>
> I was recently reviewing some activity logs and found these top 5 API 
> calls (with counts) for last Thursday:
>
>   46398 open-ils.pcrud.retrieve.au <http://open-ils.pcrud.retrieve.au>
>   41363 open-ils.actor.get_barcodes
>   33044 open-ils.pcrud.transaction.begin
>   32591 open-ils.pcrud.transaction.rollback
>   30549 open-ils.pcrud.search.atc
>
> Way down the list I have:
>
>   452 open-ils.pcrud.transaction.commit
>
> If I take out the ~450 begin/commit pairs, which perform real work, 
> I'm left with ~65k begin + rollback API calls.  That's roughly 1 of 
> every 10 API calls that hit our system.
>
> Not only are there a lot of them, each results in a begin or rollback 
> call in the database. The calls are fast and generally harmless on a 
> per-call basis, but they do make it to the database every time, so 
> they're not exactly trivial/superficial.
>
> The begin/rollback pairs are the result of using "authoritative" data 
> retrieval -- calls that start a database transaction so the caller can 
> be sure any data retrieved comes from the primary database.  This is 
> useful when a) data must be up to date to avoid confusion/oddness in 
> the UI and b) the Evergreen system is running one or more pooled 
> database replicas that handle live read queries -- live replicas can 
> occasionally lag behind with replication and return very slightly 
> older data than the primary database.
>
> For sites like KCLS, where all live queries go to one primary 
> database, these API calls serve no purpose.  (We have replicas, but 
> they are not part of an active load-balanced pool.  They are used 
> instead for reporting, bulk data collection, debugging, and of course 
> backups).
>
> Since these begin + rollback pairs (and ".authoritative" APIs) serve 
> no purpose in our environment, I was considering creating a local 
> patch to disable them.  However, before I start patching locally, I'm 
> curious if there is a broader desire for deprecating authoritative 
> APIs?  I suspect they can be turned into NO-OP's with 2 or 3 
> well-placed lines of code.
>
> Do many/any of you use live, read-only pooled database replicas?
>
> I'd love to hear your thoughts/concerns/etc.
>
> Thanks,
>
> -b
>
>
>
>
>
>
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