[SERVER-48051] Temporary namespace collisions in 4.4 mixed version cluster mapReduce tests Created: 08/May/20  Updated: 29/Oct/23  Resolved: 20/May/20

Status: Closed
Project: Core Server
Component/s: MapReduce, Sharding
Affects Version/s: None
Fix Version/s: 4.4.0-rc7

Type: Task Priority: Major - P3
Reporter: Jack Mulrow Assignee: Charlie Swanson
Resolution: Fixed Votes: 0
Labels: qopt-team
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
Backwards Compatibility: Fully Compatible
Participants:
Linked BF Score: 27

 Description   

SERVER-20057 disabled map reduce testing with more than one mongos because the temporary namespace chosen for concurrent sharded cluster mapReduces on different routers can collide. SERVER-43303 enabled this testing because this problem doesn't exist for the new mapReduce implementation. If this testing runs in a 4.4 mixed version cluster though, the old protocol is still used because each mongos uses the 4.2 binary, which can lead to failures.

Either the testing enabled by SERVER-43303 should be disabled in mixed version clusters or the way legacy sharded mapReduce generates temporary namespaces should be fixed, possibly by using a UUID as the namespace suffix instead of a concatenation of the current time and an atomic counter.



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

Author:

{'name': 'Charlie Swanson', 'email': 'charlie.swanson@mongodb.com', 'username': 'cswanson310'}

Message: SERVER-48051 Avoid known namespace conflict on concurrent mapReduces

We know that the implementation of mapReduce on a 4.2 mongos will choose
a namespace for mapReduce results to be sent to temporarily, and the
name is not unique enough. This patch blacklists mixed-version testing
of mapReduce in the concurrency suite.
Branch: v4.4
https://github.com/mongodb/mongo/commit/b2b65781fd8695292d737355c583c5d83774d8a1

Comment by Jack Mulrow [ 08/May/20 ]

SERVER-43303 was completed by the query team, so assigning this ticket to their backlog user.

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