When trying to update the index settings via UpdateSettings API, we are running into an issue when updating non dynamic settings, gives an impression that the settings has been applied but actually its not the case.

Scenario 1:
updating dynamic settings

curl -XPUT localhost:9200/testindex/_settings -d '{"index":{"number_of_replicas":"3"}}'

the request succeeds with

{"ok":true}

Scenario 2:
updating non dynamic settings

curl -XPUT localhost:9200/testindex/_settings -d '{"index":{"cache.filter.max_size":"-1"}}'

the request succeeds with

{"ok":true}

and has a log entry

[White Pilgrim] [testindex] ignoring non dynamic index level settings for open indices: [index.cache.filter.max_size]

Shouldn't the Scenario 2 be failing with the same error message instead of the log entry?