Open PIT swaps skipped & failed _shards results

[benchaplin]

Elasticsearch Version

9.1.0-SNAPSHOT

Installed Plugins

No response

Java Version

bundled

OS Version

N/A

Problem Description

Open PIT request returns the number of failed shards in the "skipped" field and the number of skipped shards in the "failed" field.

Looks like the bug has been in place since partial search was added to PIT (#111516).

I believe the fix is just to pass values in the correct order here:

elasticsearch/server/src/main/java/org/elasticsearch/action/search/OpenPointInTimeResponse.java

Line 62 in 8bcb0c4

buildBroadcastShardsHeader(builder, params, totalShards, successfulShards, failedShards, skippedShards, null);

elasticsearch/server/src/main/java/org/elasticsearch/rest/action/RestActions.java

Lines 80 to 88 in 8bcb0c4

	public static XContentBuilder buildBroadcastShardsHeader(
	XContentBuilder builder,
	Params params,
	int total,
	int successful,
	int skipped,
	int failed,
	ShardOperationFailedException[] shardFailures
	) throws IOException {

Though we also clearly need to fill a gap in testing.

Steps to Reproduce

1. Start a 2 node cluster
2. Put an index with 2 shards

PUT /test
{
    "settings": {
        "index": {
            "number_of_shards": 2,
            "number_of_replicas": 0
        }
    }
}

3. Stop one of the nodes (therefore making a shard unavailable).
4. Open a PIT allowing partial search results

POST /test/_pit?keep_alive=1m&allow_partial_search_results=true
-> {
  "id": "...",
  "_shards": {
    "total": 2,
    "successful": 1,
    "skipped": 1,
    "failed": 0
  }
}

There should be 1 shard failed, not 1 skipped. For instance, a normal search gives:

GET /test/_search
-> {
  "took": 2,
  "timed_out": false,
  "_shards": {
    "total": 2,
    "successful": 1,
    "skipped": 0,
    "failed": 1,
    "failures": [
      {
        "shard": 1,
        "index": "test",
        "node": null,
        "reason": {
          "type": "no_shard_available_action_exception",
          "reason": null
        }
      }
    ]
  },
  "hits": {
    "total": {
      "value": 0,
      "relation": "eq"
    },
    "max_score": null,
    "hits": []
  }
}

Logs (if relevant)

No response

[elasticsearchmachine]

Pinging @elastic/es-search-foundations (Team:Search Foundations)

[javanna]

good catch!