Empty dir error in datanode inplace migration

[todvora]

Empty opensearch_data_location should be reported as invalid configuration for the inplace migration. If it's empty and users are trying to migrate, it's most likely an error in configuration, their actual data is somewhere else that they are telling us.

/nocl

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[moesterheld]

I would not stop them from migrating, only warn them. Without remote reindexing, this is currently the only way to switch to data node if you don't care about migrating data

[todvora]

@moesterheld added warnings to the compatibility check and remove the error in case of empty data directory.

@gally47 could you please extend the frontend implementation, so it displays warning? The current response format looks like this:

{
  "tdvorak-ThinkPad-T14s-Gen-1": {
    "hostname": "tdvorak-ThinkPad-T14s-Gen-1",
    "opensearch_version": "2.15.0",
    "info": {
      "nodes": [],
      "opensearch_data_location": "/home/tdvorak/bin/datanode/data"
    },
    "compatibility_errors": [],
    "compatibility_warnings": [
      "Your configured opensearch_data_location directory /home/tdvorak/bin/datanode/data doesn't contain any indices! Migration can't continue!"
    ]
  }
}

[todvora]

Thanks @gally47, the frontend now works perfectly! Tested locally and everything looks good.

[moesterheld]

Tested and works fine. Backend lgtm, frontend as well.