[SERVER-37557] Add startup warning about enableMajorityReadConcern and usage of arbiters Created: 10/Oct/18  Updated: 29/Oct/23  Resolved: 06/Nov/18

Status: Closed
Project: Core Server
Component/s: Replication
Affects Version/s: None
Fix Version/s: 3.6.10, 4.0.5, 4.1.5

Type: Task Priority: Major - P3
Reporter: William Schultz (Inactive) Assignee: Vesselina Ratcheva (Inactive)
Resolution: Fixed Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Backports
Related
related to SERVER-42573 Only warn about readConcernMajority e... Closed
Backwards Compatibility: Fully Compatible
Backport Requested:
v4.0, v3.6
Sprint: Repl 2018-11-05, Repl 2018-11-19
Participants:
Case:

 Description   

We want to add a startup warning that alerts users if enableReadConcernMajority is set to true on a node that is part of a replica set that contains an arbiter. It will read as follows:

This replica set uses arbiters, but readConcern:majority is enabled for this node. This is not a recommended configuration. Please see <link to documentation>.



 Comments   
Comment by Tess Avitabile (Inactive) [ 21/Nov/18 ]

The warning will apply for all versions that support arbiters, so it sounds like there is no need to pin this to 4.2.

Comment by Kay Kim (Inactive) [ 21/Nov/18 ]

When 4.2 goes out, we will have https://dochub.mongodb.org/core/psa-disable-rc-majority point to docs.mongodb.com/manual/.... (which will correspond to 4.2) and thereafter, it will point to the latest GA version.

If that warning will no longer apply or differ for versions greater than 4.2, I can definitely have it pinned to 4.2 version.

Comment by Tess Avitabile (Inactive) [ 20/Nov/18 ]

No problem! I'm not sure if we will need to update the master link in the future. kay.kim, what do you think?

Comment by Vesselina Ratcheva (Inactive) [ 20/Nov/18 ]

Question: would we need to eventually update the master link to say 4.2?

Comment by Githook User [ 20/Nov/18 ]

Author:

{'name': 'Vesselina Ratcheva', 'email': 'vesselina.ratcheva@10gen.com', 'username': 'vessy-mongodb'}

Message: SERVER-37557 fix doc link
Branch: v3.6
https://github.com/mongodb/mongo/commit/c06a21f2efa258f8ea13ad1cda900b537ad00a94

Comment by Githook User [ 20/Nov/18 ]

Author:

{'name': 'Vesselina Ratcheva', 'email': 'vesselina.ratcheva@10gen.com', 'username': 'vessy-mongodb'}

Message: SERVER-37557 fix doc link
Branch: v4.0
https://github.com/mongodb/mongo/commit/4bc36a8707cf9394155b903a3f5b8c4ebed2bf4f

Comment by Vesselina Ratcheva (Inactive) [ 20/Nov/18 ]

tess.avitabile Yikes, sorry I overlooked that. On it.

Comment by Tess Avitabile (Inactive) [ 20/Nov/18 ]

vesselina.ratcheva, can you please change the startup warning to use the link that Kay specified for each branch?

Comment by Githook User [ 19/Nov/18 ]

Author:

{'name': 'Vesselina Ratcheva', 'email': 'vesselina.ratcheva@10gen.com', 'username': 'vessy-mongodb'}

Message: SERVER-37557 Add startup warning about enableMajorityReadConcern and usage of arbiters

(cherry picked from commit 1f40ed56b27d9c98c23eb601d6b06116b194dfe7)
Branch: v4.0
https://github.com/mongodb/mongo/commit/ac99b600745b488968257d936d8fad0f755c4f1c

Comment by Githook User [ 19/Nov/18 ]

Author:

{'name': 'Vesselina Ratcheva', 'email': 'vesselina.ratcheva@10gen.com', 'username': 'vessy-mongodb'}

Message: SERVER-37557 Add startup warning about enableMajorityReadConcern and usage of arbiters

(cherry picked from commit 1f40ed56b27d9c98c23eb601d6b06116b194dfe7)
Branch: v3.6
https://github.com/mongodb/mongo/commit/fd0aac9d3f762520c6159a2335c70194fb62148e

Comment by Githook User [ 06/Nov/18 ]

Author:

{'name': 'Vesselina Ratcheva', 'email': 'vesselina.ratcheva@10gen.com', 'username': 'vessy-mongodb'}

Message: SERVER-37557 Add startup warning about enableMajorityReadConcern and usage of arbiters
Branch: master
https://github.com/mongodb/mongo/commit/1f40ed56b27d9c98c23eb601d6b06116b194dfe7

Comment by Tess Avitabile (Inactive) [ 23/Oct/18 ]

Thank you, kay.kim!

The risk is greatest in a 3-member PSA, since you only need one data-bearing node to go down in order to lose majority writes. However, the risk exists in any set with an arbiter, since they allow you to accept writes when the majority commit point cannot move forward. We are going to recommend all sets with arbiters use enableMajorityReadConcern:"false".

Comment by Tess Avitabile (Inactive) [ 19/Oct/18 ]

kay.kim, what documentation link should we use for each branch (master, 4.0, and 3.6)?

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