[SERVER-49893] Create oplog fetcher for resharding Created: 25/Jul/20  Updated: 29/Oct/23  Resolved: 01/Oct/20

Status: Closed
Project: Core Server
Component/s: Sharding
Affects Version/s: None
Fix Version/s: 4.8.0

Type: Task Priority: Major - P3
Reporter: Max Hirschhorn Assignee: Daniel Gottlieb (Inactive)
Resolution: Fixed Votes: 0
Labels: PM-234-M2, PM-234-T-oplog-fetch
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
is depended on by SERVER-49894 Have resharding oplog fetcher resume ... Closed
is depended on by SERVER-49897 Insert no-op entries into oplog buffe... Closed
Gantt Dependency
has to be done after SERVER-49891 Write and test aggregation pipeline f... Closed
Problem/Incident
Backwards Compatibility: Fully Compatible
Sprint: Sharding 2020-09-21, Sharding 2020-10-05
Participants:
Linked BF Score: 48

 Description   

The oplog fetcher for resharding should take the aggregation pipeline from SERVER-49891, run it against a particular donor, and insert the returned documents into the oplog buffer collection on itself (a recipient).

  • Serialize the aggregation pipeline from createOplogFetchingPipelineForResharding() using Pipeline::serializeToBson() and use the serialized form to create an AggregationRequest.
  • Add the necessary read concern and hint to the AggregationRequest.
  • Run the aggregate command on the remote donor. We likely don't want to use ClusterAggregate::runAggregate() because we want a recipient to target each donor with a unique aggregation pipeline (unique due to different resume points).
  • Use Collection::insertDocuments() to insert the documents into the new sharded collection.


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

Author:

{'name': 'Daniel Gottlieb', 'email': 'daniel.gottlieb@mongodb.com', 'username': 'dgottlieb'}

Message: SERVER-49893: Do oplog fetching.
Branch: master
https://github.com/mongodb/mongo/commit/d286a563d4ad921331d7d3846181a5bb7192a31d

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