Don't track stats when project ID is null

Author: nicktindall

server/src/main/java/org/elasticsearch/repositories/SnapshotMetrics.java

@@ -11,7 +11,6 @@
 
 import org.elasticsearch.cluster.metadata.ProjectId;
 import org.elasticsearch.cluster.metadata.RepositoryMetadata;
-import org.elasticsearch.core.Nullable;
 import org.elasticsearch.telemetry.metric.DoubleHistogram;
 import org.elasticsearch.telemetry.metric.LongCounter;
 import org.elasticsearch.telemetry.metric.LongWithAttributes;
@@ -85,11 +84,8 @@ public void createSnapshotsInProgressMetric(Supplier<Collection<LongWithAttribut
         meterRegistry.registerLongsGauge(SNAPSHOTS_IN_PROGRESS, "snapshots in progress", "unit", snapshotsInProgressObserver);
     }
 
-    public static Map<String, Object> createAttributesMap(@Nullable ProjectId projectId, RepositoryMetadata meta) {
-        if (projectId == null) {
-            return Map.of("repo_type", meta.type(), "repo_name", meta.name());
-        } else {
-            return Map.of("project_id", projectId.id(), "repo_type", meta.type(), "repo_name", meta.name());
-        }
+    public static Map<String, Object> createAttributesMap(ProjectId projectId, RepositoryMetadata meta) {
+        assert projectId != null : "Project ID should always be set";
+        return Map.of("project_id", projectId.id(), "repo_type", meta.type(), "repo_name", meta.name());
     }
 }

server/src/main/java/org/elasticsearch/repositories/blobstore/BlobStoreSnapshotMetrics.java

@@ -36,8 +36,14 @@ public class BlobStoreSnapshotMetrics {
     private final Map<String, Object> metricAttributes;
 
     public BlobStoreSnapshotMetrics(@Nullable ProjectId projectId, RepositoryMetadata repositoryMetadata, SnapshotMetrics snapshotMetrics) {
-        this.snapshotMetrics = snapshotMetrics;
-        metricAttributes = SnapshotMetrics.createAttributesMap(projectId, repositoryMetadata);
+        if (projectId != null) {
+            this.snapshotMetrics = snapshotMetrics;
+            metricAttributes = SnapshotMetrics.createAttributesMap(projectId, repositoryMetadata);
+        } else {
+            // Project ID should only be null for the stateless main blobstore, which is not used for snapshots
+            this.snapshotMetrics = SnapshotMetrics.NOOP;
+            this.metricAttributes = Map.of();
+        }
     }
 
     public void incrementSnapshotRateLimitingTimeInNanos(long throttleTimeNanos) {