[SERVER-79660] use mirrored reads to warm hidden nodes Created: 03/Aug/23  Updated: 08/Aug/23

Status: Backlog
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Improvement Priority: Major - P3
Reporter: Eric Milkie Assignee: Backlog - Service Architecture
Resolution: Unresolved Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
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Assigned Teams:
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 Description   

Newly restarted nodes in a replica set suffer from a cold cache, which can make secondary reads directed to such nodes experience longer latencies.
Making use of the hidden replica set configuration flag is one technique to hide such "warming" nodes from secondary reads.
Today, we only use mirrored reads in the server to keep secondaries somewhat warm in order to improve primary hand-off. It should be possible to use mirrored reads to also expedite the warming of such hidden nodes, as an optional feature. The idea would be that we could mirror, say, 100% of reads on a primary to any nodes that are currently healthy and hidden. It would be left to an external mechanism to decide when to turn this feature on, and when to reconfigure the replica set to add or remove the hidden property from nodes.
Credit to max.hirschhorn@mongodb.com for this idea!



 Comments   
Comment by Phoebe Du [ 08/Aug/23 ]

shameek.ray@mongodb.com will follow up on the product side. Sending this ticket to backlog.

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