Fix active_shards_percent_as_number NaN when state not recovered

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

@@ -16,6 +16,7 @@
 import org.elasticsearch.action.support.PlainActionFuture;
 import org.elasticsearch.cluster.health.ClusterHealthStatus;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
+import org.elasticsearch.cluster.metadata.Metadata;
 import org.elasticsearch.cluster.routing.UnassignedInfo;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.Priority;
@@ -56,8 +57,14 @@ public void testSimpleLocalHealth() {
     }
 
     public void testHealth() {
+        logger.info("--> running cluster health for '_all' on an empty cluster");
+        ClusterHealthResponse healthResponse = clusterAdmin().prepareHealth(TEST_REQUEST_TIMEOUT, Metadata.ALL).get();
+        assertThat(healthResponse.isTimedOut(), equalTo(false));
+        assertThat(healthResponse.getStatus(), equalTo(ClusterHealthStatus.GREEN));
+        assertThat(healthResponse.getIndices().isEmpty(), equalTo(true));
+
         logger.info("--> running cluster health on an index that does not exists");
-        ClusterHealthResponse healthResponse = clusterAdmin().prepareHealth(TEST_REQUEST_TIMEOUT, "test1")
+        healthResponse = clusterAdmin().prepareHealth(TEST_REQUEST_TIMEOUT, "test1")
             .setWaitForYellowStatus()
             .setTimeout(TimeValue.timeValueSeconds(1))
             .get();

server/src/internalClusterTest/java/org/elasticsearch/synonyms/SynonymsManagementAPIServiceIT.java

@@ -15,6 +15,7 @@
 import org.elasticsearch.action.bulk.BulkResponse;
 import org.elasticsearch.cluster.ClusterName;
 import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.index.mapper.extras.MapperExtrasPlugin;
 import org.elasticsearch.indices.IndexCreationException;
 import org.elasticsearch.plugins.Plugin;
@@ -316,11 +317,7 @@ public void testCreateSynonymsWithYellowSynonymsIndex() throws Exception {
             @Override
             void checkSynonymsIndexHealth(ActionListener<ClusterHealthResponse> listener) {
                 ClusterState clusterState = ClusterState.builder(ClusterName.DEFAULT).build();
-                ClusterHealthResponse response = new ClusterHealthResponse(
-                    randomIdentifier(),
-                    new String[] { SynonymsManagementAPIService.SYNONYMS_INDEX_CONCRETE_NAME },
-                    clusterState
-                );
+                ClusterHealthResponse response = new ClusterHealthResponse(randomIdentifier(), Strings.EMPTY_ARRAY, clusterState);
                 response.setTimedOut(true);
                 listener.onResponse(response);
             }

server/src/main/java/org/elasticsearch/cluster/health/ClusterIndexHealth.java

@@ -56,10 +56,29 @@ public ClusterIndexHealth(final IndexMetadata indexMetadata, final IndexRoutingT
         this.numberOfReplicas = indexMetadata.getNumberOfReplicas();
 
         shards = new HashMap<>();
-        for (int i = 0; i < indexRoutingTable.size(); i++) {
-            IndexShardRoutingTable shardRoutingTable = indexRoutingTable.shard(i);
-            int shardId = shardRoutingTable.shardId().id();
-            shards.put(shardId, new ClusterShardHealth(shardId, shardRoutingTable));
+        if (indexRoutingTable != null) {
+            for (int i = 0; i < indexRoutingTable.size(); i++) {
+                IndexShardRoutingTable shardRoutingTable = indexRoutingTable.shard(i);
+                int shardId = shardRoutingTable.shardId().id();
+                shards.put(shardId, new ClusterShardHealth(shardId, shardRoutingTable));
+            }
+        } else {
+            for (int shardId = 0; shardId < numberOfShards; shardId++) {
+                // Create a shard health representing completely unassigned shard
+                // All replicas for this shard are unassigned, including the primary
+                int replicasCount = numberOfReplicas + 1;
+                ClusterShardHealth clusterShardHealth = new ClusterShardHealth(
+                    shardId,
+                    ClusterHealthStatus.RED,
+                    0,
+                    0,
+                    0,
+                    replicasCount,
+                    1,
+                    false
+                );
+                shards.put(shardId, clusterShardHealth);
+            }
         }
 
         // update the index status

server/src/main/java/org/elasticsearch/cluster/health/ClusterStateHealth.java

@@ -84,12 +84,16 @@ public ClusterStateHealth(
         int totalShardCount = 0;
 
         for (String index : concreteIndices) {
-            IndexRoutingTable indexRoutingTable = routingTable.index(index);
             IndexMetadata indexMetadata = project.index(index);
-            if (indexRoutingTable == null) {
+            if (indexMetadata == null) {
+                // should not happen, concreteIndices ought to have been resolved against the project metadata
+                assert false : "concrete index [" + index + "] not found in project [" + project.id() + "]";
+                computeStatus = ClusterHealthStatus.RED;
                 continue;
             }
 
+            IndexRoutingTable indexRoutingTable = routingTable.index(index);
+
             ClusterIndexHealth indexHealth = new ClusterIndexHealth(indexMetadata, indexRoutingTable);
             indices.put(indexHealth.getIndex(), indexHealth);
 
@@ -121,7 +125,7 @@ public ClusterStateHealth(
 
         // shortcut on green
         if (computeStatus.equals(ClusterHealthStatus.GREEN)) {
-            this.activeShardsPercent = 100;
+            this.activeShardsPercent = 100.0;
         } else {
             this.activeShardsPercent = (((double) this.activeShards) / totalShardCount) * 100;
         }

server/src/test/java/org/elasticsearch/action/admin/cluster/health/ClusterHealthResponsesTests.java

@@ -16,7 +16,6 @@
 import org.elasticsearch.cluster.health.ClusterIndexHealth;
 import org.elasticsearch.cluster.health.ClusterIndexHealthTests;
 import org.elasticsearch.cluster.health.ClusterStateHealth;
-import org.elasticsearch.cluster.metadata.Metadata;
 import org.elasticsearch.common.io.stream.BytesStreamOutput;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -161,7 +160,7 @@ public void testClusterHealth() throws IOException {
         TimeValue pendingTaskInQueueTime = TimeValue.timeValueMillis(randomIntBetween(1000, 100000));
         ClusterHealthResponse clusterHealth = new ClusterHealthResponse(
             "bla",
-            new String[] { Metadata.ALL },
+            new String[0], // Use empty array since clusterState has no indices
             clusterState,
             clusterState.metadata().getProject().id(),
             pendingTasks,

server/src/test/java/org/elasticsearch/action/admin/cluster/health/TransportClusterHealthActionTests.java

@@ -23,6 +23,7 @@
 import org.elasticsearch.cluster.routing.ShardRoutingState;
 import org.elasticsearch.cluster.routing.TestShardRouting;
 import org.elasticsearch.common.Randomness;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.core.Tuple;
 import org.elasticsearch.index.IndexVersion;
@@ -75,7 +76,7 @@ public void testWaitForAllShards() {
 
         clusterState = ClusterState.builder(ClusterName.DEFAULT).build();
         project = clusterState.metadata().getProject(Metadata.DEFAULT_PROJECT_ID);
-        response = createResponse(indices, clusterState, project);
+        response = createResponse(Strings.EMPTY_ARRAY /* no indices */ , clusterState, project);
         assertThat(TransportClusterHealthAction.prepareResponse(request, response, project, null), equalTo(1));
     }
 

server/src/test/java/org/elasticsearch/cluster/health/ClusterStateHealthTests.java

@@ -19,6 +19,9 @@
 import org.elasticsearch.cluster.ClusterName;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.TestShardRoutingRoleStrategies;
+import org.elasticsearch.cluster.block.ClusterBlock;
+import org.elasticsearch.cluster.block.ClusterBlockLevel;
+import org.elasticsearch.cluster.block.ClusterBlocks;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.metadata.Metadata;
@@ -41,6 +44,7 @@
 import org.elasticsearch.common.util.set.Sets;
 import org.elasticsearch.index.IndexVersion;
 import org.elasticsearch.indices.TestIndexNameExpressionResolver;
+import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.tasks.CancellableTask;
 import org.elasticsearch.tasks.TaskId;
 import org.elasticsearch.test.ESTestCase;
@@ -633,6 +637,64 @@ private boolean primaryInactiveDueToRecovery(final String indexName, final Clust
         return true;
     }
 
+    /**
+     * Tests the case where indices exist in metadata but their routing tables are missing.
+     * This happens during cluster restart where metadata is loaded but routing table is not yet built.
+     * All shards should be considered completely unassigned and the cluster should be RED.
+     */
+    public void testActiveShardsPercentDuringClusterRestart() {
+        final String indexName = "test-idx";
+        ProjectId projectId = randomUniqueProjectId();
+
+        final IndexMetadata indexMetadata = IndexMetadata.builder(indexName)
+            .settings(settings(IndexVersion.current()).put(IndexMetadata.SETTING_INDEX_UUID, UUIDs.randomBase64UUID()))
+            .numberOfShards(3)
+            .numberOfReplicas(1)
+            .build();
+
+        // Create cluster state with index metadata but WITHOUT routing table entry
+        // This simulates cluster restart where metadata is loaded but routing table is not yet built
+        final var mdBuilder = Metadata.builder().put(ProjectMetadata.builder(projectId).put(indexMetadata, true).build());
+        final var rtBuilder = GlobalRoutingTable.builder().put(projectId, RoutingTable.EMPTY_ROUTING_TABLE);
+
+        ClusterState clusterState = ClusterState.builder(new ClusterName("test_cluster"))
+            .metadata(mdBuilder.build())
+            .routingTable(rtBuilder.build())
+            .blocks(
+                ClusterBlocks.builder()
+                    .addGlobalBlock(new ClusterBlock(1, "test", true, true, true, RestStatus.SERVICE_UNAVAILABLE, ClusterBlockLevel.ALL))
+            )
+            .build();
+
+        String[] concreteIndices = new String[] { indexName };
+        ClusterStateHealth clusterStateHealth = new ClusterStateHealth(clusterState, concreteIndices, projectId);
+
+        // The cluster should be RED because all shards are unassigned
+        assertThat(clusterStateHealth.getStatus(), equalTo(ClusterHealthStatus.RED));
+
+        // All shards are unassigned, so activeShardsPercent should be 0.0
+        assertThat(
+            "activeShardsPercent should be 0.0 when all shards are unassigned",
+            clusterStateHealth.getActiveShardsPercent(),
+            equalTo(0.0)
+        );
+
+        // Verify that totalShardCount is correctly calculated
+        int expectedTotalShards = indexMetadata.getTotalNumberOfShards();
+        assertThat("All shards should be counted as unassigned", clusterStateHealth.getUnassignedShards(), equalTo(expectedTotalShards));
+
+        // All primary shards should be unassigned
+        assertThat(
+            "All primary shards should be unassigned",
+            clusterStateHealth.getUnassignedPrimaryShards(),
+            equalTo(indexMetadata.getNumberOfShards())
+        );
+
+        // No active shards
+        assertThat(clusterStateHealth.getActiveShards(), equalTo(0));
+        assertThat(clusterStateHealth.getActivePrimaryShards(), equalTo(0));
+    }
+
     private void assertClusterHealth(ClusterStateHealth clusterStateHealth, RoutingTableGenerator.ShardCounter counter) {
         assertThat(clusterStateHealth.getStatus(), equalTo(counter.status()));
         assertThat(clusterStateHealth.getActiveShards(), equalTo(counter.active));

server/src/test/java/org/elasticsearch/rest/action/cat/RestIndicesActionTests.java

@@ -151,7 +151,8 @@ public void testBuildTable() {
             IndexStats indexStats = indicesStats.get(indexName);
             IndexMetadata indexMetadata = project.index(indexName);
 
-            if (indexHealth != null) {
+            IndexRoutingTable indexRoutingTable = clusterState.routingTable(project.id()).index(indexName);
+            if (indexRoutingTable != null) {
                 assertThat(row.get(0).value, equalTo(indexHealth.getStatus().toString().toLowerCase(Locale.ROOT)));
             } else if (indexStats != null) {
                 assertThat(row.get(0).value, equalTo("red*"));