[SERVER-52924] Donor shards may create config.cache.chunks for temporary resharding collection after calculating their minFetchTimestamp Created: 18/Nov/20  Updated: 29/Oct/23  Resolved: 01/Dec/20

Status: Closed
Project: Core Server
Component/s: Sharding
Affects Version/s: None
Fix Version/s: 4.9.0

Type: Bug Priority: Major - P3
Reporter: Max Hirschhorn Assignee: Blake Oler
Resolution: Fixed Votes: 0
Labels: PM-234-M2, PM-234-T-lifecycle
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Backwards Compatibility: Fully Compatible
Operating System: ALL
Sprint: Sharding 2020-11-30, Sharding 2020-12-14
Participants:
Story Points: 1

 Description   

Problem Description

Recipient shards expect to read from the donor shard's existing sharded collection and the config.cache.chunks collection of the temporary resharding collection using {atClusterTime: <fetchTimestamp>}. Refreshing the temporary resharding collection on the donor shards causes them to create the config.cache.chunks.<database>.system.resharding.<existingUUID> collection. If this config.cache.chunks collection is created after the minFetchTimestamp, then the {atClusterTime: <fetchTimestamp>} read on it would fail with a SnapshotUnavailable error response. (Or a NamespaceNotFound error response if the donor shards weren't also recipient shards.)

Donor shards must instead create the config.cache.chunks for temporary resharding collection before calculating their minFetchTimestamp.

Solution

  • Trigger a catalog cache refresh for the temporary resharding collection, on the DonorStateMachine, before calculating the fetchTimestamp.
  • Remove the refresh that's marked under this ticket's number as a TODO on the coordinator's state machine.


 Comments   
Comment by Githook User [ 01/Dec/20 ]

Author:

{'name': 'Blake Oler', 'email': 'blake.oler@mongodb.com', 'username': 'BlakeIsBlake'}

Message: SERVER-52924 Refresh temporary collection on donor shard before creating minFetchTimestamp
Branch: master
https://github.com/mongodb/mongo/commit/9b15b5a07c8e47e9be4f886ce7c6076fd5c66e87

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