Adding a new command to check for cluster wide sharding metadata consistency

Description of Linked Ticket

Summary

We need a command or aggregation that users (and Atlas) can run to check that the collection metadata (e.g. UUIDs) is consistent across all shards.

Motivation

In the last months we have seen an increasing number of HELP tickets with the same issue: there was a sharded collection that had different UUID across shards. Usually, this sharded collection had different UUIDs because at some point the customer performed some operations directly against the shards, without going through a mongos. Despite the fact that PM-2689 will disallow direct operations against the shards, we see value in adding a way to verify that the collection metadata of a sharded collection is consistent across shards.

The reason why this issue is spotted since 5.0 is that on that version we introduced the renameCollection operation that verifies, before renaming the collection locally on a shard, that the local UUID matches the expected one.

Documentation

Product Description
Scope Document
Technical Design Document
Docs Update