[BUG] Cluster State Stats Fails For Multi Node Setup

[amkhar]

Describe the bug
curl localhost:9200/_nodes/stats?pretty fails with following exception

{
  "error" : {
    "root_cause" : [
      {
        "type" : "illegal_argument_exception",
        "reason" : "Field name cannot be null"
      }
    ],
    "type" : "illegal_argument_exception",
    "reason" : "Field name cannot be null",
    "suppressed" : [
      {
        "type" : "illegal_state_exception",
        "reason" : "Failed to close the XContentBuilder",
        "caused_by" : {
          "type" : "i_o_exception",
          "reason" : "Unclosed object or array found"
        }
      }
    ]
  },
  "status" : 400
}

To Reproduce
Steps to reproduce the behavior:

1. Create a multi node cluster
2. Run _nodes/stats

Expected behavior
_nodes/stats should always work fine for single node or multi node clusters

Additional context
Recently cluster state stats were added #10670 which is causing this issue.

[amkhar]

Root cause : It was happening as statsName field is not being written on stream and while creating PersistedStateStats object it's not being set.

Resolution : Write statsName field on stream and read it to set it in the object.

Stack trace

[2023-10-27T15:57:11,821][INFO ][o.o.c.c.PersistedStateStats] [clusterManager2] stats name null
[2023-10-27T15:57:11,821][WARN ][stderr                   ] [clusterManager2] java.lang.IllegalArgumentException: Field name cannot be null
[2023-10-27T15:57:11,822][WARN ][stderr                   ] [clusterManager2] 	at org.opensearch.core.xcontent.XContentBuilder.ensureNotNull(XContentBuilder.java:1058)
[2023-10-27T15:57:11,822][WARN ][stderr                   ] [clusterManager2] 	at org.opensearch.core.xcontent.XContentBuilder.ensureNameNotNull(XContentBuilder.java:1053)
[2023-10-27T15:57:11,822][WARN ][stderr                   ] [clusterManager2] 	at org.opensearch.core.xcontent.XContentBuilder.field(XContentBuilder.java:314)
[2023-10-27T15:57:11,822][WARN ][stderr                   ] [clusterManager2] 	at org.opensearch.core.xcontent.XContentBuilder.startObject(XContentBuilder.java:291)
[2023-10-27T15:57:11,822][WARN ][stderr                   ] [clusterManager2] 	at org.opensearch.cluster.coordination.PersistedStateStats.toXContent(PersistedStateStats.java:76)
[2023-10-27T15:57:11,822][WARN ][stderr                   ] [clusterManager2] 	at org.opensearch.cluster.service.ClusterStateStats.toXContent(ClusterStateStats.java:107)
[2023-10-27T15:57:11,822][WARN ][stderr                   ] [clusterManager2] 	at org.opensearch.discovery.DiscoveryStats.toXContent(DiscoveryStats.java:93)
[2023-10-27T15:57:11,823][WARN ][stderr                   ] [clusterManager2] 	at org.opensearch.action.admin.cluster.node.stats.NodeStats.toXContent(NodeStats.java:545)
[2023-10-27T15:57:11,823][WARN ][stderr                   ] [clusterManager2] 	at org.opensearch.action.admin.cluster.node.stats.NodesStatsResponse.toXContent(NodesStatsResponse.java:78)
[2023-10-27T15:57:11,823][WARN ][stderr                   ] [clusterManager2] 	at org.opensearch.rest.action.RestActions.nodesResponse(RestActions.java:223)