auto date histogram error in mixed version cluster

[nik9000]

While working on the backport to #54161 I discovered a new and unique error that is almost certainly my fault:

        "failures" : [
          {
            "shard" : 1,
            "index" : "test",
            "node" : "OmBZbfyERlKeciJo0vK2QA",
            "reason" : {
              "type" : "transport_serialization_exception",
              "reason" : "Failed to deserialize response from handler [org.elasticsearch.transport.TransportService$ContextRestoreResponseHandler]",
              "caused_by" : {
                "type" : "exception",
                "reason" : "unknown rounding id [85]"
              }
            }
          }
        ]

[elasticmachine]

Pinging @elastic/es-analytics-geo (:Analytics/Aggregations)

[nik9000]

This isn't related to the change I'm backporting but the new test that I'm writing discovers it. The failure comes when running against a 6.8.8 mixed version cluster.

[nik9000]

I'm totally unsure which version fix has this bug. I'll figure it out on Monday when I can concentrate on it properly.

[imotov]

@nik9000 have you ever figured this one out?

[nik9000]

Looks like I got it in #54447. Sorry for the trouble!