[BUG] `NodesInfoResponse` serializes `total_indexing_buffer` and `total_indexing_buffer_in_bytes` swapped

[Xtansia]

Describe the bug

When retrieving node info total_indexing_buffer_in_bytes should be the raw byte count (e.g. 53687091) and total_indexing_buffer should be the human readable version (e.g. 51.1mb). This is currently swapped and is against the patterns set out by other human byte count properties.

This discrepancy was introduced >8 years ago: ebc3c17#diff-0f31418774699d0487aba335ddccd8942599b4a9999e92e2932bcfb6a22aa392
The two explicit fields were merged to use on of the "human readable field" XContentBuilder methods to enable use of the ?human parameter, however the parameters to byteSizeField were swapped.

Related component

Cluster Manager

To Reproduce

1. Execute GET /_nodes?human&filter_path=nodes.*.total_indexing_buffer*
2. See the response:

{
  "nodes": {
    "741KuezCTUaGy0RDV7oxEA": {
      "total_indexing_buffer_in_bytes": "51.1mb",
      "total_indexing_buffer": 53687091
    },
    "eTLqEyRiQzaxSYdZ1KbfVA": {
      "total_indexing_buffer_in_bytes": "51.1mb",
      "total_indexing_buffer": 53687091
    }
  }
}

Expected behavior

The total_indexing_buffer_in_bytes field should contain the raw byte count and the total_indexing_buffer field should contain the human readable version.

Additional Details

No response

[rajiv-kv]

[Triage - attendees 1 2 3]
Thanks @Xtansia for filing the issue. This seems to be different from the pattern used by stats API.
Please feel free to raise the fix.

[hye-on]

Hi, @Xtansia

Can I work on this? I see a few options:

1. Directly swap the field values:
   total_indexing_buffer <-> total_indexing_buffer_in_bytes

2. Add new fields with different names for backward compatibility

3. Handle it with version check:

Version currentVersion = Version.CURRENT;
if (currentVersion.onOrAfter(Version.V_3_0_0)) {
    builder.humanReadableField("total_indexing_buffer_in_bytes", "total_indexing_buffer", nodeInfo.getTotalIndexingBuffer());
} else {
    builder.humanReadableField("total_indexing_buffer", "total_indexing_buffer_in_bytes", nodeInfo.getTotalIndexingBuffer());
}

Thank you, and I look forward to your feedback :)

[Xtansia]

@hye-on Feel free to pick this up!
Swapping the fields will technically be a breaking change, so it will need to be either behind a version check or just not backported to 2.x and only merged into main, not sure on the general preference. I think adding new fields with different names is likely to add more confusion than it helps.