Why setting `inflight_requests.type` is not supported?

[ViggoC (Viggo)]

I found out that add inflight_requests.type in elasticsearch.yml is not supported, but request.type is ok.

uncaught exception in thread [main]
java.lang.IllegalArgumentException: unknown setting [network.breaker.inflight_requests.type] did you mean any of [network.breaker.inflight_requests.limit, network.breaker.inflight_requests.overhead]?

Reading the code found that only type setting of filed data and request are registered in ClusterSettings.

HierarchyCircuitBreakerService.FIELDDATA_CIRCUIT_BREAKER_TYPE_SETTING,
HierarchyCircuitBreakerService.REQUEST_CIRCUIT_BREAKER_TYPE_SETTING,

What are the considerations. Or is it just because of negligence?

[DavidTurner]

It does look like an oversight to me. However, AFAIK none of the network.breaker.*.type settings are documented and I don't think it makes much sense for an end-user to change them.

[ViggoC (Viggo)]

In fact, I am just confused that one circuit breaker can be configured and the other cannot be configured. Will there be any problems if I register this setting in ClusterSetting?

And, there are currently some settings in the ES source code without corresponding documentation. eg. indices.id_field_data.enabled. So for what purpose were they developed if they are not encouraged to use?

[DavidTurner]

There are quite a few settings that are deliberately undocumented and only intended for internal use, e.g. in tests, or to switch on some internally-controlled behaviour.