Elasticsearch date-index-name-processor when set to week, always create w52

[Ioxxy]

Hello there,

I'm using Elasticsearch v7.16.2.
I'm working for a client, and it's impossible for them to change the elastic output to change the index name. My goal is to change the daily format to a weekly one.

To do so, I'm using the ingest pipeline date-index-name processor.
The problem is, when I simulate / test the pipeline I got what I want, but when I apply it, the week is always week number 52.
Do you have an explaination for this ?

The test :

POST _ingest/pipeline/_simulate
{
  "pipeline" :
  {
    "description": "test",
    "processors" : [
  {
      "date_index_name": {
        "field": "@timestamp",
        "date_rounding": "M",
        "index_name_prefix": "index-cagnottage-",
        "index_name_format": "yyyy-MM",
        "if": "ctx.process == 'SECURITY'"
      }
    },
    {
      "date_index_name": {
        "field": "@timestamp",
        "date_rounding": "w",
        "index_name_prefix": "kubernetes_cluster-",
        "index_name_format": "yyyy-ww"
      }
    }
]
  },
  "docs": [
    {
      "_source": {
        "@timestamp": "2022-08-17T07:25:57.530Z"
      }
    }
  ]
}

Test result :

{
  "docs" : [
    {
      "doc" : {
        "_index" : "<kubernetes_cluster-{2022-33||/w{yyyy-ww|UTC}}>",
        "_type" : "_doc",
        "_id" : "_id",
        "_source" : {
          "@timestamp" : "2022-08-17T07:25:57.530Z"
        },
        "_ingest" : {
          "timestamp" : "2022-08-17T08:08:17.311457476Z"
        }
      }
    }
  ]
}

Reality result (done with the same @timestamp as the test) :

kubernetes_cluster-2021-52

Note : The first date_index_name to root few documents out of the main index is working fine.

Note 2 : When date rounding is set to w, I get year 2021,
when I set date rouding to m, I get year 2022, complete non sense to me...

Thank you for your help.