[DOCS-13610] Investigate changes in SERVER-47189: Do a safe reconfig to add config term on upgrade to FCV=4.4 Created: 23/Apr/20  Updated: 13/Nov/23  Due: 01/May/20  Resolved: 08/May/20

Status: Closed
Project: Documentation
Component/s: manual
Affects Version/s: None
Fix Version/s: 4.4.0-rc1, Server_Docs_20231030, Server_Docs_20231106, Server_Docs_20231105, Server_Docs_20231113

Type: Task Priority: Major - P3
Reporter: Backlog - Core Eng Program Management Team Assignee: Ravind Kumar (Inactive)
Resolution: Done Votes: 0
Labels: docs-replication
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Documented
documents SERVER-47189 Do a safe reconfig to add config term... Closed
Related
related to DOCS-13482 Investigate changes in SERVER-46288: ... Closed
Participants:
Days since reply: 3 years, 39 weeks, 5 days ago
Epic Link: DOCS: 4.4 Server Release Work

 Description   

Description

Downstream Change Summary

On upgrade to 4.4 starting from RC1, the primary executes a similar reconfig to add the term field from the on-disk config document and blocks waiting for only a majority of the nodes to replicate the new config. This is sufficient to guarantee the new on-disk format will eventually propagate to all nodes and the next primary must have the new on-disk format. This is an optimization to avoid potential safety issues on the later transition from 4.2-style config to safe reconfig.

Description of Linked Ticket

When replica set nodes are in FCV=4.2, their replica set configs have no config "term" field. This is intentional so that the behavior in FCV=4.2 matches the v4.2 reconfig behavior. After upgrading to FCV=4.4, however, replica set nodes will not add a config term until the first safe reconfig is run. This can leave an indefinitely long period of time where nodes will have configs with uninitialized terms, which is unsafe for the reasons illustrated in the trace of this comment. To prevent this unsafe period of time after upgrade, we should do an internal no-op reconfig after upgrading to FCV=4.4 to automatically add config terms, analogous to what we do on FCV downgrade.

Scope of changes

Impact to Other Docs

MVP (Work and Date)

Resources (Scope or Design Docs, Invision, etc.)



 Comments   
Comment by Githook User [ 08/May/20 ]

Author:

{'name': 'rk-mongo', 'email': 'ravind.kumar@mongodb.com', 'username': 'rkumar-mongo'}

Message: DOCS-13610: new field for replica configuration
Branch: master
https://github.com/mongodb/docs/commit/d2f2d33055b4e768fe11a0c017e9833f282de850

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