[SERVER-72142] Define catalog shard changelog behaviour Created: 15/Dec/22  Updated: 03/Mar/23  Resolved: 03/Mar/23

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Task Priority: Major - P3
Reporter: Kshitij Gupta Assignee: Jack Mulrow
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Related
related to SERVER-73409 Handle tenant migrations for a catalo... Closed
Assigned Teams:
Sharding NYC
Sprint: Sharding NYC 2023-03-06
Participants:

 Description   

Lines

 

https://github.com/mongodb/mongo/blob/d4082c855140f25957d9ad9be6b8056413be9d3e/src/mongo/db/commands/run_aggregate.cpp#L777

 

https://github.com/mongodb/mongo/blob/d4082c855140f25957d9ad9be6b8056413be9d3e/src/mongo/db/repl/replication_coordinator_impl.cpp#L355



 Comments   
Comment by Jack Mulrow [ 03/Mar/23 ]

From talking with didier.nadeau@mongodb.com and milkie@mongodb.com on slack, we don't expect to use a colocated config server in serverless anytime soon, so it's fine to keep serverless change streams disallowed on the config server for now and we can revisit in the future. So since no code changes are required for this ticket, I'm closing it as "done."

Comment by Jack Mulrow [ 01/Mar/23 ]

The second check is for the periodic noop writer's interval. It uses a shorter interval so there's frequent enough activity to avoid stalling change streams waiting for oplog entries. It's probably not necessary for a shard that has user data since it'll see more frequent writes, but I don't see a harm in having it enabled. And the catalog shard is still the one config server, so if it is idle, we'd still want the more frequent noops.

As for the first check, that seems like an assertion for a kind of change streams that only exist in a serverless environment. I'm not sure we even use sharding in serverless yet, but I'm guessing we'll want to lift that restriction so eventually we can use catalog shards in serverless with change streams. I'll follow up with the serverless team.

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