Fixed assertion unsafe call of ClusterService.state() (opensearch-project#19775)

* Fixed assertion unsafe call of ClusterService.state()

Signed-off-by: Nils Bandener <nils.bandener@eliatra.com>

* Added changelog

Signed-off-by: Nils Bandener <nils.bandener@eliatra.com>

---------

Signed-off-by: Nils Bandener <nils.bandener@eliatra.com>

Author: nibix

CHANGELOG.md

@@ -40,6 +40,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [Java Agent] Allow JRT protocol URLs in protection domain extraction ([#19683](https://github.com/opensearch-project/OpenSearch/pull/19683))
 - Fix potential concurrent modification exception when updating allocation filters ([#19701])(https://github.com/opensearch-project/OpenSearch/pull/19701))
 - Fix file-based ingestion consumer to handle start point beyond max line number([#19757])(https://github.com/opensearch-project/OpenSearch/pull/19757))
+- Fixed assertion unsafe use of ClusterService.state() in ResourceUsageCollectorService ([#19775])(https://github.com/opensearch-project/OpenSearch/pull/19775))
 
 ### Dependencies
 - Update to Gradle 9.1 ([#19575](https://github.com/opensearch-project/OpenSearch/pull/19575))

server/src/main/java/org/opensearch/node/ResourceUsageCollectorService.java

@@ -126,7 +126,7 @@ public NodesResourceUsageStats stats() {
      * Fetch local node resource usage statistics and add it to store along with the current timestamp
      */
     private void collectLocalNodeResourceUsageStats() {
-        if (nodeResourceUsageTracker.isReady() && clusterService.state() != null) {
+        if (nodeResourceUsageTracker.isReady() && clusterService.isStateInitialised()) {
             collectNodeResourceUsageStats(
                 clusterService.state().nodes().getLocalNodeId(),
                 System.currentTimeMillis(),