Re:D1: Our SQL database
by smarx007 on Wednesday May 11, 2022 @10:50AM
(#31340774)
"D1 will create read-only clones of your data, close to where your users are, and constantly keep them up-to-date with changes."
Sounds like there will be no synchronous replication and instead there will be a background process to "constantly keep [read-only clones] up-to-date". This means that a stale read from an older read replica can occur even after a write transaction has successfully committed on the "primary" used for writes.
So, while the consistency is not "thrown away", it's no longer a strong consistency? Anyway, Kyle from Jepsen will figure it out soon, I guess :)
Re:D1: Our SQL database
by geelen on Wednesday May 11, 2022 @11:29AM
(#31341439)
Yeah, so you can always opt-in to strong consistency by transferring execution to the primary (see the "Embedded Compute" section of the blog). Then it's pretty much exactly the same as a DO.
Sounds like there will be no synchronous replication and instead there will be a background process to "constantly keep [read-only clones] up-to-date". This means that a stale read from an older read replica can occur even after a write transaction has successfully committed on the "primary" used for writes.
So, while the consistency is not "thrown away", it's no longer a strong consistency? Anyway, Kyle from Jepsen will figure it out soon, I guess :)