Closed
Description
When trying to upgrade an index with custom similarity settings from 7.1.0, the node fails to start with an exception similar to "Caused by: java.lang.IllegalArgumentException: Unknown settings for similarity of type [BM25]: [normalization.h2.c, normalization, after_effect, basic_model]" . We observed this happening upgrading from 7.1.0 to 7.5.0 and also from 7.1.0 to 7.1.1 . This appears to be the same issue as #25350.
To reproduce, start up a 7.1.0 cluster, and apply the following settings:
PUT /i
{
"settings": {
"index": {
"similarity": {
"my_similarity": {
"after_effect": "l",
"basic_model": "g",
"normalization": "h2",
"normalization.h2.c": "3.0",
"type": "DFR"
}
}
}
}
}
Then attempt to upgrade that cluster. (Thank you @DaveCTurner for concise repro steps)