[COMPASS-6208] Investigate changes in PM-2290: Make dedicated config servers optional for sharded clusters Created: 17/Oct/22  Updated: 12/Jun/23  Resolved: 03/May/23

Status: Closed
Project: Compass
Component/s: None
Affects Version/s: None
Fix Version/s: No version

Type: Investigation Priority: Major - P3
Reporter: Backlog - Core Eng Program Management Team Assignee: Unassigned
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
Epic Link: COMPASS-5987
Documentation Changes: Not Needed

 Description   
Original Downstream Change Summary

The design document has more details about the changes which is being reviewed in WRITING-8015.

User-Facing Syntax Changes
Users will need to modify the change management scripts if they wish to opt-in into new mode
Users will need to make the startup script roll forward/back compatible
Users will need to write the script performing the roll forward/back procedure

API Changes
The internal SDAM protocol is likely to change. Will write SDAM tests, no spec changes required (do we have a document for internal SDAM extensions?).
We will avoid adding a new API version

Config File Changes
The new “catalogShard” option is added to the "sharding.clusterRole" section of the config file, “--catalogShard” command line option is added to the mongod.

Description of Linked Ticket

+underlined text+

Epic Summary

Summary

We will make dedicated config servers optional for sharded clusters. Customers will have the option to designate a special shard that will hold both user data and config data. For one-shard clusters on Atlas, the shard will automatically be a special shard with both the shard role and config role.

Motivation

Eliminating dedicated config servers will reduce both the cost and the architectural complexity involved in single-shard sharded clusters. On Atlas, a single-shard M30 sharded cluster costs TWICE as much as an M30 replica set. This project would bring cost parity to single-shard clusters on Atlas and will make it easier for customers to start out with a sharded cluster or switch to a sharded cluster.

It also supports other use-cases:

  • Serverless v2 - Serverless would like to remove the cost and complexity of dealing with config servers.
  • Kubernetes - Some customers prefer to use a sharded cluster with a single shard because the mongos can act as a proxy. No config server would mean better resource utilization and less operational overhead

Cast of Characters

Documentation

Product Description
Scope Document
Technical Design Document



 Comments   
Comment by PM Bot [ 12/Jun/23 ]

Fix Version updated for upstream PM-2290:
7.0.0-rc0

Comment by Le Roux Bodenstein [ 03/May/23 ]

This does not affect dev tools.

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