InternalClusterInfoService should not ignore hidden indices (#62995)

Today InternalClusterInfoService ignores hidden indices when 
retrieving shard stats of the cluster. This can lead to suboptimal 
shard allocation decisions as the size of shards are taken into 
account when allocating new shards or rebalancing existing shards.

server/src/internalClusterTest/java/org/elasticsearch/cluster/ClusterInfoServiceIT.java

@@ -41,8 +41,10 @@ import org.elasticsearch.index.IndexService;
 import org.elasticsearch.index.shard.IndexShard;
 import org.elasticsearch.index.store.Store;
 import org.elasticsearch.indices.IndicesService;
+import org.elasticsearch.indices.SystemIndexDescriptor;
 import org.elasticsearch.plugins.ActionPlugin;
 import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.plugins.SystemIndexPlugin;
 import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.test.InternalTestCluster;
 import org.elasticsearch.test.transport.MockTransportService;
@@ -52,6 +54,7 @@ import org.hamcrest.Matchers;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
+import java.util.Locale;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -70,7 +73,9 @@ import static org.hamcrest.Matchers.greaterThanOrEqualTo;
 @ESIntegTestCase.ClusterScope(scope = ESIntegTestCase.Scope.TEST, numDataNodes = 0)
 public class ClusterInfoServiceIT extends ESIntegTestCase {
 
-    public static class TestPlugin extends Plugin implements ActionPlugin {
+    private static final String TEST_SYSTEM_INDEX_NAME = ".test-cluster-info-system-index";
+
+    public static class TestPlugin extends Plugin implements ActionPlugin, SystemIndexPlugin {
 
         private final BlockingActionFilter blockingActionFilter;
 
@@ -82,6 +87,11 @@ public class ClusterInfoServiceIT extends ESIntegTestCase {
         public List<ActionFilter> getActionFilters() {
             return singletonList(blockingActionFilter);
         }
+
+        @Override
+        public Collection<SystemIndexDescriptor> getSystemIndexDescriptors(Settings settings) {
+            return List.of(new SystemIndexDescriptor(TEST_SYSTEM_INDEX_NAME, "System index for [" + getTestClass().getName() + ']'));
+        }
     }
 
     public static class BlockingActionFilter extends org.elasticsearch.action.support.ActionFilter.Simple {
@@ -117,13 +127,18 @@ public class ClusterInfoServiceIT extends ESIntegTestCase {
 
     public void testClusterInfoServiceCollectsInformation() {
         internalCluster().startNodes(2);
-        assertAcked(prepareCreate("test").setSettings(Settings.builder()
-            .put(Store.INDEX_STORE_STATS_REFRESH_INTERVAL_SETTING.getKey(), 0)
-            .put(EnableAllocationDecider.INDEX_ROUTING_REBALANCE_ENABLE_SETTING.getKey(), EnableAllocationDecider.Rebalance.NONE).build()));
+
+        final String indexName = randomBoolean() ? randomAlphaOfLength(5).toLowerCase(Locale.ROOT) : TEST_SYSTEM_INDEX_NAME;
+        assertAcked(prepareCreate(indexName)
+            .setSettings(Settings.builder()
+                .put(Store.INDEX_STORE_STATS_REFRESH_INTERVAL_SETTING.getKey(), 0)
+                .put(EnableAllocationDecider.INDEX_ROUTING_REBALANCE_ENABLE_SETTING.getKey(), EnableAllocationDecider.Rebalance.NONE)
+                .put(IndexMetadata.SETTING_INDEX_HIDDEN, randomBoolean())
+                .build()));
         if (randomBoolean()) {
-            assertAcked(client().admin().indices().prepareClose("test"));
+            assertAcked(client().admin().indices().prepareClose(indexName));
         }
-        ensureGreen("test");
+        ensureGreen(indexName);
         InternalTestCluster internalTestCluster = internalCluster();
         // Get the cluster info service on the master node
         final InternalClusterInfoService infoService = (InternalClusterInfoService) internalTestCluster

server/src/main/java/org/elasticsearch/cluster/InternalClusterInfoService.java

@@ -206,7 +206,7 @@ public class InternalClusterInfoService implements ClusterInfoService, ClusterSt
         final IndicesStatsRequest indicesStatsRequest = new IndicesStatsRequest();
         indicesStatsRequest.clear();
         indicesStatsRequest.store(true);
-        indicesStatsRequest.indicesOptions(IndicesOptions.STRICT_EXPAND_OPEN_CLOSED);
+        indicesStatsRequest.indicesOptions(IndicesOptions.STRICT_EXPAND_OPEN_CLOSED_HIDDEN);
 
         client.admin().indices().stats(indicesStatsRequest, new LatchedActionListener<>(listener, latch));
         return latch;
@@ -222,7 +222,7 @@ public class InternalClusterInfoService implements ClusterInfoService, ClusterSt
      */
     public final ClusterInfo refresh() {
         logger.trace("refreshing cluster info");
-        final CountDownLatch nodeLatch = updateNodeStats(new ActionListener<NodesStatsResponse>() {
+        final CountDownLatch nodeLatch = updateNodeStats(new ActionListener<>() {
             @Override
             public void onResponse(NodesStatsResponse nodesStatsResponse) {
                 ImmutableOpenMap.Builder<String, DiskUsage> leastAvailableUsagesBuilder = ImmutableOpenMap.builder();
@@ -252,7 +252,7 @@ public class InternalClusterInfoService implements ClusterInfoService, ClusterSt
             }
         });
 
-        final CountDownLatch indicesLatch = updateIndicesStats(new ActionListener<IndicesStatsResponse>() {
+        final CountDownLatch indicesLatch = updateIndicesStats(new ActionListener<>() {
             @Override
             public void onResponse(IndicesStatsResponse indicesStatsResponse) {
                 final ShardStats[] stats = indicesStatsResponse.getShards();
@@ -348,8 +348,8 @@ public class InternalClusterInfoService implements ClusterInfoService, ClusterSt
     }
 
     static void fillDiskUsagePerNode(Logger logger, List<NodeStats> nodeStatsArray,
-            ImmutableOpenMap.Builder<String, DiskUsage> newLeastAvaiableUsages,
-            ImmutableOpenMap.Builder<String, DiskUsage> newMostAvaiableUsages) {
+            ImmutableOpenMap.Builder<String, DiskUsage> newLeastAvailableUsages,
+            ImmutableOpenMap.Builder<String, DiskUsage> newMostAvailableUsages) {
         for (NodeStats nodeStats : nodeStatsArray) {
             if (nodeStats.getFs() == null) {
                 logger.warn("Unable to retrieve node FS stats for {}", nodeStats.getNode().getName());
@@ -380,7 +380,7 @@ public class InternalClusterInfoService implements ClusterInfoService, ClusterSt
                                 nodeId, leastAvailablePath.getTotal().getBytes());
                     }
                 } else {
-                    newLeastAvaiableUsages.put(nodeId, new DiskUsage(nodeId, nodeName, leastAvailablePath.getPath(),
+                    newLeastAvailableUsages.put(nodeId, new DiskUsage(nodeId, nodeName, leastAvailablePath.getPath(),
                         leastAvailablePath.getTotal().getBytes(), leastAvailablePath.getAvailable().getBytes()));
                 }
                 if (mostAvailablePath.getTotal().getBytes() < 0) {
@@ -389,7 +389,7 @@ public class InternalClusterInfoService implements ClusterInfoService, ClusterSt
                                 nodeId, mostAvailablePath.getTotal().getBytes());
                     }
                 } else {
-                    newMostAvaiableUsages.put(nodeId, new DiskUsage(nodeId, nodeName, mostAvailablePath.getPath(),
+                    newMostAvailableUsages.put(nodeId, new DiskUsage(nodeId, nodeName, mostAvailablePath.getPath(),
                         mostAvailablePath.getTotal().getBytes(), mostAvailablePath.getAvailable().getBytes()));
                 }