I am asking this on behalf of a colleague.
He is using Elasticsearch 2.3.3 and they got an index corruption.
They decided to delete one folder representing the name of the index which was corrupted.
After that, they discovered no index was more present.
Some logs were mentioning:
java.lang.IllegalArgumentException: Could not load codec 'Lucene54'. Did you forget to add lucene-backward-codecs...
What would be the root cause of that?