[DOCS-14300] Investigate changes in SERVER-54908: Shard servers with 4.9 binary and 4.4 FCV should be able to use secondaryDelaySecs Created: 17/Mar/21  Updated: 13/Nov/23  Due: 28/May/21

Status: Closed
Project: Documentation
Component/s: manual, Server
Affects Version/s: None
Fix Version/s: 4.9.0, 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: Unassigned
Resolution: Won't Do Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Documented
documents SERVER-54908 Shard servers with 4.9 binary and 4.4... Closed
documents SERVER-54962 Test that 4.4 nodes do not silently i... Closed
Gantt End to End
Related
Participants:
Days since reply: 1 year, 14 weeks, 2 days ago
Epic Link: DOCSP-15042
Story Points: 2

 Description   

Description

Downstream Change Summary

We should document the manual downgrade procedure for a shard server binary that attempted to downgrade to 4.4 with the secondaryDelaySecs field still present. We point users to this link: http://www.mongodb.org/dochub/core/recover-replica-set-from-invalid-config so it should be updated accordingly.

The test goes through the following procedure:
1. Start up a shard server process with MDB 4.9 / FCV (featureCompatibilityVersion) 4.4 (note: new shard servers will default to the last-LTS FCV until they are added to a sharded cluster via addShard)
2. Call rs.init() with secondaryDelaySecs in the replica set config.
3. Downgrade shard binary to MDB 4.4 / FCV 4.4 by stopping the shard server and restarting with "binary: 4.4". During this step, the shard server will refuse to start up because it sees an unrecognized field (secondaryDelaySecs). In order for the user to get out of this situation, they'll have to do the following:

  • Restart shard with MDB 4.9 ("binary: 4.9") / FCV 4.4.
  • Reconfig to change 'secondaryDelaySecs' to 'slaveDelay'.
  • Downgrade shard binary to MDB 4.4 / FCV 4.4 by restarting shard with "binary: 4.4". The shard server should successfully start up.

Note: This is specific to downgrading to 4.4 from 5.0.

Description of Linked Ticket

New 4.9 shard servers use the default 4.4 FCV, and therefore reject secondaryDelaySecs, until either:

  • they are added to a cluster with 4.9 FCV (via addShard)
  • they are added to a cluster with 4.4 FCV and the FCV is then set to 4.9 for the entire cluster via mongos

During this period, we should allow shard servers to initialize with secondaryDelaySecs since they are using the 4.9 binary.

Scope of changes

Impact to Other Docs

MVP (Work and Date)

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



 Comments   
Comment by Education Bot [ 31/Oct/22 ]

Hello! This ticket has been closed due to inactivity. If you believe this ticket is still important, please reopen it and leave a comment to explain why. Thank you!

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