Rollover API failing with 400 in case settings name don't have "index." prefix or "index" section in json

[shwetathareja]

Elasticsearch version (bin/elasticsearch --version): 7.6

Plugins installed: []

Description of the problem including expected versus actual behavior:
Rollover API takes index settings as input parameters. The settings can specified as one of the below options:

1.  "settings": {
      "index" : {
    	"number_of_shards": 2
      }
  }
 2.  "settings": {
    "index.number_of_shards": 2
  }
3. "settings": {
    "number_of_shards": 2
  }

But, with this PR. the #3 option doesn't work and throws error as

{
  "error" : {
    "root_cause" : [
      {
        "type" : "illegal_argument_exception",
        "reason" : "unknown setting [number_of_shards] did you mean [index.number_of_shards]?"
      }
    ],
    "type" : "illegal_argument_exception",
    "reason" : "unknown setting [number_of_shards] did you mean [index.number_of_shards]?"
  },
  "status" : 400
}

Fix:
There is normalize and settings validation logic in onlyCreateIndex method and after refactoring this code is not getting triggered during rollover flow which calls applyCreateIndexRequest method.

Settings.Builder updatedSettingsBuilder = Settings.builder();
        Settings build = updatedSettingsBuilder.put(request.settings()).normalizePrefix(IndexMetaData.INDEX_SETTING_PREFIX).build();
        indexScopedSettings.validate(build, true); // we do validate here - index setting must be consistent
        request.settings(build);

The normalize call should also run during rollover flow otherwise it breaks the expected behavior.

Steps to reproduce:

1. curl -XPUT localhost:9200/abc-000001
2. curl -XPUT localhost:9200/abc-000001/_alias/abc
3. curl -X POST "localhost:9200/abc/_rollover?pretty" -H 'Content-Type: application/json' -d'
{
"conditions": {
"max_age":   "1s"
},
"settings": {
"number_of_shards": 2
}
}
'

Tried running this in 7.5 with no issue and rollover works as expected.

[elasticmachine]

Pinging @elastic/es-core-features (:Core/Features/ILM+SLM)

[shwetathareja]

Hi Team,

If we are aligned on the issue and the fix. I can pick it up.

[andreidan]

Thanks for using ILM and reporting this bug @shwetathareja
Feel free to work on a fix for this and let us know if you need any help.

[shwetathareja]

Sure andreidan@, Sorry for the delay. I will pick it up.

[Gaurav614]

Talked to @shwetathareja about this opened issue and wanted to pickup the implementation of it.
I will start working on this issue and will raise the PR for it shortly

[pugnascotia]

Closed by #57271.

[jbaiera]

Closing for real this time