Fix get all inference endponts not returning multiple endpoints sharing model deployment

[dan-rubinstein]

Description

Issue - https://github.com/elastic/ml-team/issues/1470?reload=1?reload=1

We currently have a bug when calling the get all inference endpoints API that only returns a single endpoint for each model deployment. This is happening because after we retrieve all the endpoints from the inference index, we call the deployment stats API to accurately return the current num_allocations but in doing so, we accidentally filter out all but the last retrieve inference endpoint for each model deployment. This change updates the logic to properly handle multiple endpoints for a single model deployment.

Testing

• Unit tests
• Locally tested by creating multiple endpoints for a single model deployment and ensuring that both endpoints are returned. Also confirmed that updating a single endpoints num_allocations will reflect in all endpoints sharing the same model deployment when calling to get all inference endpoints.

[elasticsearchmachine]

Hi @dan-rubinstein, I've created a changelog YAML for you.

[elasticsearchmachine]

Pinging @elastic/ml-core (Team:ML)

[jonathan-buttner]

Hey Dan 👋 do you want this change to go to 8.18.0? I see it's labeled for 9.0.0. 8.18 and 9.0 are being released together so if we're targeting one we should probably do both.

[jonathan-buttner]

nit: I think the if-else can be distilled to something like this:

modelsByDeploymentIds.merge(
  esModel.mlNodeDeploymentId(),
  new ArrayList<String>(List.of(esModel)), (a, b) -> {
    a.addAll(b);
    return a;
});

[dan-rubinstein]

Nice, I like this method much better! I'll go ahead and make that change.

[dan-rubinstein]

@elasticmachine merge upstream

[elasticsearchmachine]

💔 Backport failed

The backport operation could not be completed due to the following error:

An unexpected error occurred when attempting to backport this PR.

You can use sqren/backport to manually backport by running backport --upstream elastic/elasticsearch --pr 121821