MongoDB 4.2 Distributed Transaction with Arbiter
We are preparing to introduce MongoDB 4.2 and expect distributed transaction function.
I read document which arbiter don't be member when use distributed transaction.
PSA can do that, but it's weird that it doesn't even work out to PSSA.
It usually operates as a PSS from an operating point of view, but can temporarily become a PSA in the event of equipment problems.
Why should there be no Arbiter in the Shard to use Distributed Transaction?
I can not understand restriction.
Can you tell me technical reason for not being able to support Distributed Transaction with Arbiter?
Do you have plans to improve in the next version?
The issue with arbiters is they do not accept writes and therefore cannot contribute to majority write concern acknowledgement which distributed transactions rely on.
There is no plan at this point to allow distributed transactions with arbiter.
As a side note, PSSA is a bad configuration to have since having four nodes means majority is three and therefore it doesn't give you any advantage over PSS cluster. Both can only acknowledge majority write concern writes when at most one data holding node is down. With one secondary gone, PSS cluster still has majority available. No reason to ever use PSSA that I can see.