[SERVER-49929] Policy for placing system collections in admin or config DB Created: 27/Jul/20  Updated: 08/Jan/24  Resolved: 05/Oct/20

Status: Closed
Project: Core Server
Component/s: Replication
Affects Version/s: None
Fix Version/s: 4.9.0

Type: New Feature Priority: Major - P3
Reporter: A. Jesse Jiryu Davis Assignee: A. Jesse Jiryu Davis
Resolution: Fixed Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
depends on SERVER-48878 Remove admin X-lock promotion Closed
Backwards Compatibility: Fully Compatible
Sprint: Repl 2020-09-21, Repl 2020-10-05, Repl 2020-10-19
Participants:

 Description   

The "admin" and "config" databases each contain a handful of system collections, holding replica set or sharding state. I think the admin and config DBs were historically distinguished by different locking rules, but these days there is no rationale for keeping them separate.

Let's consider merging them. However, it seems likely that merging them is more difficult than it's worth. In that case, let's add to the Replication Architecture Guide some information about these two databases, and a policy for where new system collections are placed as we develop new features in the future.



 Comments   
Comment by Githook User [ 05/Oct/20 ]

Author:

{'name': 'A. Jesse Jiryu Davis', 'email': 'jesse@mongodb.com', 'username': 'ajdavis'}

Message: SERVER-49929 Describe system collections in arch guide
Branch: master
https://github.com/mongodb/mongo/commit/03b9dce2762f3ebc8989f9802f982eb7e855a2be

Comment by Kaloian Manassiev [ 29/Jul/20 ]

I don't think it is true that we don't allow transactions on the config database. We certainly use transactions for refining the document shard key (blake.oler to confirm). Perhaps it's only certain config collections that disallow it?

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