PCSM-283 Skip sharding operations for replica set

[rasika-chivate]

Add topology migration from Sharded Cluster to Replicaset.

For details, see the following ticket:

https://perconadev.atlassian.net/browse/PCSM-283

[Copilot]

🟡 Changes recommended

The documentation contains contradictory requirements and broken examples that could mislead users.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

Suppressed comments (4)

docs/sharding.md:25

• The new replica-set target option is documented as added in 0.10.0, but the prerequisite immediately above still permits PCSM 0.7.0. This would lead users of 0.7–0.9 to attempt an unsupported topology; make the minimum version topology-specific.

* The source must be a sharded MongoDB deployment.
* The target can be either a sharded MongoDB deployment or a replica set.

docs/sharded-source-to-replica-set-target.md:42

• The opening code delimiter is misplaced inside target-user, so only part of this environment-variable assignment is rendered as code and the example cannot be copied cleanly. Wrap the complete assignment consistently with the source URI above.

* Verify that PCSM can connect to both the source sharded cluster and the target replica set.

docs/sharded-source-to-replica-set-target.md:47

• This statement is broader than the implemented behavior described on line 17. Only shardCollection is skipped; other unsupported sharding commands such as movePrimary and unshardCollection still fail replication according to docs/limitations.md:37. Name the skipped operation explicitly.
  docs/sharded-source-to-replica-set-target.md:66
• Step 9 asks readers to inspect the logs from this run, but this invocation does not save them. Client subcommands write logs to stderr (docs/logging.md:67-74), so restore stderr redirection to create the log that will be checked later.

        ```

• Files reviewed: 4/4 changed files
• Comments generated: 2
• Review effort level: Balanced

[Copilot]

🟡 Changes recommended

Version guidance, URI syntax, migration prerequisites, and workflow instructions contain unresolved inaccuracies.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

Suppressed comments (5)

docs/sharding.md:17

• This sentence applies “different numbers of shards” to both target topologies, but a replica set has no shards. Limit that statement to the sharded-target case so the topology description remains accurate.

In both cases, the source must be a sharded MongoDB deployment. The source and target can have different numbers of shards, and a replica set target does not require a target `mongos` instance.

docs/sharded-source-to-replica-set-target.md:41

• The examples are not in one code block, and the stray backtick in target-userbreaks the target username and Markdown rendering. Present both complete environment assignments in a fenced block withtarget-user` intact.

    `PCSM_SOURCE_URI="mongodb://source-user:password@mongos-source:27017/admin"`
    PCSM_TARGET_URI="mongodb://target-`user:password@target1:27017,target2:27017,target3:27017/admin?replicaSet=rs0"`

docs/sharded-source-to-replica-set-target.md:53

• The singular noun after “the other” is missing an article. This also switches from the page's established “target” terminology to “destination”; use a parallel source/target description.

    1. Create two clusters, one sharded (source) and the other replica set (destination).

docs/sharded-source-to-replica-set-target.md:92

• These commands are described as running only on the target, so their output cannot establish that counts match the source. Instruct readers to run the same queries against both deployments before comparing the results.

    6. Confirm that both collections are present on the target and that document counts match:

docs/sharded-source-to-replica-set-target.md:107

• Finalization can still be in progress when the first status request runs (docs/install/usage.md:171-175), so one immediate check is not guaranteed to produce the shown finalized response. Tell readers to poll until that state is reached.

    8. Check the status again:

• Files reviewed: 4/4 changed files
• Comments generated: 3
• Review effort level: Balanced

[Copilot]

🟡 Changes recommended

Version guidance, URI syntax, migration prerequisites, and workflow instructions contain unresolved inaccuracies....

Updated the source/target wording, clarified that finalization status should be polled until it reaches finalized, and narrowed the shard-count guidance to the sharded-target case.