[SERVER-33763] 3.6 drivers fail to communicate with 3.6 sharded clusters running at FCV 3.4 Created: 08/Mar/18  Updated: 08/Jan/24  Resolved: 14/Mar/18

Status: Closed
Project: Core Server
Component/s: Sharding
Affects Version/s: 3.6.0
Fix Version/s: 3.6.4

Type: Bug Priority: Blocker - P1
Reporter: Kaloian Manassiev Assignee: Randolph Tan
Resolution: Fixed Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
is depended on by SERVER-37631 Disable logical sessions if FCV is 3.4 Closed
Documented
Related
related to SERVER-36104 LogicalSessions should destroy cache ... Closed
Backwards Compatibility: Fully Compatible
Operating System: ALL
Sprint: Sharding 2018-03-26
Participants:
Case:

 Description   

In 3.6 the MongoDB drivers added implicit support for sessions, which is triggered by the presence of the logicalSessionTimeoutMinutes field in the isMaster response.

In 3.6, MongoS will always set its internal FCV to 3.6, regardless of the FCV of the shards and as a result it will always report logicalSessionTimeoutMinutes in the isMaster response. This, combined with the drivers' spec means that the driver will always send session information, regardless of the FCV version of the shards.

Shards, which are at FCV 3.4 will reject any requests which contain session information and this essentially means that 3.6 drivers cannot be used to talk to a cluster which is at FCV 3.4.



 Comments   
Comment by Githook User [ 14/Mar/18 ]

Author:

{'email': 'randolph@10gen.com', 'name': 'Randolph Tan', 'username': 'renctan'}

Message: SERVER-33763 Add FCV checks on txnNumber when initializing session info
Branch: v3.6
https://github.com/mongodb/mongo/commit/239a5e7445381f719d7d68e821c5fc5c043c8043

Comment by Randolph Tan [ 12/Mar/18 ]

mira.carey@mongodb.com: Just want to confirm: we want to keep the logicalSessionTimeoutMinutes suppression in v3.6, right?

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