[SERVER-36557] Every command that can start a cross-shard transaction should compute atClusterTime with snapshot read concern Created: 09/Aug/18  Updated: 29/Oct/23  Resolved: 07/Sep/18

Status: Closed
Project: Core Server
Component/s: Sharding
Affects Version/s: None
Fix Version/s: 4.1.3

Type: Task Priority: Major - P3
Reporter: Jack Mulrow Assignee: Jack Mulrow
Resolution: Fixed Votes: 0
Labels: ShardedTxn:GlobalSnapshot
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Backwards Compatibility: Fully Compatible
Sprint: Sharding 2018-08-27, Sharding 2018-09-10
Participants:

 Description   

The first command in a transaction is the only one that can provide a read concern, and if a transaction runs with snapshot level read concern all targeted shards must use the same atClusterTime timestamp. This means every command that can start a transaction must be able to compute an atClusterTime so it can be sent to all shards targeted by the first statement.

These commands currently include:

  • find
  • killCursors
  • insert
  • update
  • delete
  • findAndModify
  • aggregate
  • distinct

Note: geoSearch can start a single replica set transaction, but the command is not supported on mongos

find, aggregate, and distinct already support this from the global point in time reads project, leavingĀ insert, update, delete, findAndModify, and killCursors.



 Comments   
Comment by Githook User [ 07/Sep/18 ]

Author:

{'name': 'Jack Mulrow', 'email': 'jack.mulrow@mongodb.com', 'username': 'jsmulrow'}

Message: SERVER-36557 Compute atClusterTime when killCursors is the first command in a sharded transaction
Branch: master
https://github.com/mongodb/mongo/commit/750dea991cfa27e84fb3e3deacdf2f8e292571bb

Comment by Githook User [ 06/Sep/18 ]

Author:

{'name': 'Jack Mulrow', 'email': 'jack.mulrow@mongodb.com', 'username': 'jsmulrow'}

Message: SERVER-36557 Compute atClusterTime for cluster batch writes and findAndModify
Branch: master
https://github.com/mongodb/mongo/commit/3257bb958a29a23d5101a16c49d97536e5fba056

Comment by Gregory McKeon (Inactive) [ 29/Aug/18 ]

jack.mulrow handing back to you.

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