[SERVER-68308] Write concern does not update w:0 to w:1 Created: 26/Jul/22  Updated: 05/Dec/22  Resolved: 08/Aug/22

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

Type: Bug Priority: Major - P3
Reporter: Huayu Ouyang Assignee: Backlog - Replication Team
Resolution: Won't Fix Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Related
is related to SERVER-67823 Update comments in extractWriteConcern Closed
Assigned Teams:
Replication
Operating System: ALL
Participants:

 Description   

In extractWriteConcern this comment states that w:0 is interpreted identically as w:1.

However, the place where it is supposed to be converted to w:1 never actually gets run because it is within an if (!clientSuppliedWriteConcern) statement, and w:0 is a clientSuppliedWriteConcern. There does not seem to be any other place in the codebase where w:0 would be updated to w:1. Additionally, it seems like there are some differences in the server/shell/tests in how w:0 and w:1 are treated (see scripting/mozjs/mongo.cpp, write_commands.cpp, crud_api.js, repl_set_config_validators.h, read_write_concern_defaults.cpp).

I'm not sure if this is a bug and we want to actually change w:0 to w:1, in which case this should be moved outside of the if statement, or if we do actually want to keep w:0 as a separate thing that is not interpreted identically to w:1, in which case the comment should be updated.



 Comments   
Comment by Huayu Ouyang [ 08/Aug/22 ]

I don't think w:0 writes ever become w:1 writes, even between mongos and the shards either because the conversion from w:0 to w:1 occurs only if the write concern is not "client-supplied", and w:0 counts as client-supplied.

Since it doesn't seem like this is a customer concern, we are going to keep w:0 for now but just update the comments in extractWriteConcern to be more clear. Marking this as won't fix

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