Optimize Iteration over IndexShardRoutingTable (#84987)

Move this to array as well like in #84955. This comes with a measurable speedup to reroute
as we iterate lots of very small lists in nested loops here where the iterator overhead hurts.

relates #77466

server/src/internalClusterTest/java/org/elasticsearch/action/admin/indices/create/ShrinkIndexIT.java

@@ -455,12 +455,12 @@ public void testCreateShrinkIndexFails() throws Exception {
         assertBusy(() -> {
             ClusterStateResponse clusterStateResponse = client().admin().cluster().prepareState().get();
             RoutingTable routingTables = clusterStateResponse.getState().routingTable();
-            assertTrue(routingTables.index("target").shard(0).getShards().get(0).unassigned());
+            assertTrue(routingTables.index("target").shard(0).shard(0).unassigned());
             assertEquals(
                 UnassignedInfo.Reason.ALLOCATION_FAILED,
-                routingTables.index("target").shard(0).getShards().get(0).unassignedInfo().getReason()
+                routingTables.index("target").shard(0).shard(0).unassignedInfo().getReason()
             );
-            assertEquals(1, routingTables.index("target").shard(0).getShards().get(0).unassignedInfo().getNumFailedAllocations());
+            assertEquals(1, routingTables.index("target").shard(0).shard(0).unassignedInfo().getNumFailedAllocations());
         });
         client().admin()
             .indices()
@@ -472,13 +472,7 @@ public void testCreateShrinkIndexFails() throws Exception {
         refreshClusterInfo();
         // kick off a retry and wait until it's done!
         ClusterRerouteResponse clusterRerouteResponse = client().admin().cluster().prepareReroute().setRetryFailed(true).get();
-        long expectedShardSize = clusterRerouteResponse.getState()
-            .routingTable()
-            .index("target")
-            .shard(0)
-            .getShards()
-            .get(0)
-            .getExpectedShardSize();
+        long expectedShardSize = clusterRerouteResponse.getState().routingTable().index("target").shard(0).shard(0).getExpectedShardSize();
         // we support the expected shard size in the allocator to sum up over the source index shards
         assertTrue("expected shard size must be set but wasn't: " + expectedShardSize, expectedShardSize > 0);
         ensureGreen();

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

@@ -17,6 +17,7 @@
 import org.elasticsearch.action.support.ActionFilters;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.cluster.node.DiscoveryNode;
+import org.elasticsearch.cluster.routing.IndexShardRoutingTable;
 import org.elasticsearch.cluster.routing.RoutingTable;
 import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.cluster.routing.allocation.decider.EnableAllocationDecider;
@@ -40,6 +41,7 @@
 import org.elasticsearch.transport.TransportService;
 import org.hamcrest.Matchers;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
@@ -210,7 +212,7 @@ public void testClusterInfoServiceInformationClearOnError() {
         prepareCreate("test").setSettings(Settings.builder().put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 1)).get();
         ensureGreen("test");
 
-        final List<ShardRouting> shardRoutings = client().admin()
+        final IndexShardRoutingTable indexShardRoutingTable = client().admin()
             .cluster()
             .prepareState()
             .clear()
@@ -219,8 +221,11 @@ public void testClusterInfoServiceInformationClearOnError() {
             .getState()
             .getRoutingTable()
             .index("test")
-            .shard(0)
-            .shards();
+            .shard(0);
+        final List<ShardRouting> shardRoutings = new ArrayList<>(indexShardRoutingTable.size());
+        for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+            shardRoutings.add(indexShardRoutingTable.shard(copy));
+        }
 
         InternalTestCluster internalTestCluster = internalCluster();
         InternalClusterInfoService infoService = (InternalClusterInfoService) internalTestCluster.getInstance(

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

@@ -309,14 +309,16 @@ private IndexRoutingTable randomChangeToIndexRoutingTable(IndexRoutingTable orig
         for (int i = 0; i < original.size(); i++) {
             IndexShardRoutingTable indexShardRoutingTable = original.shard(i);
             Set<String> availableNodes = Sets.newHashSet(nodes);
-            for (ShardRouting shardRouting : indexShardRoutingTable.shards()) {
+            for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+                ShardRouting shardRouting = indexShardRoutingTable.shard(copy);
                 availableNodes.remove(shardRouting.currentNodeId());
                 if (shardRouting.relocating()) {
                     availableNodes.remove(shardRouting.relocatingNodeId());
                 }
             }
 
-            for (ShardRouting shardRouting : indexShardRoutingTable) {
+            for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+                ShardRouting shardRouting = indexShardRoutingTable.shard(copy);
                 final ShardRouting updatedShardRouting = randomChange(shardRouting, availableNodes);
                 availableNodes.remove(updatedShardRouting.currentNodeId());
                 if (shardRouting.relocating()) {

server/src/internalClusterTest/java/org/elasticsearch/cluster/allocation/AwarenessAllocationIT.java

@@ -15,7 +15,7 @@
 import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.cluster.metadata.IndexMetadata.State;
 import org.elasticsearch.cluster.routing.IndexRoutingTable;
-import org.elasticsearch.cluster.routing.ShardRouting;
+import org.elasticsearch.cluster.routing.IndexShardRoutingTable;
 import org.elasticsearch.cluster.routing.allocation.decider.AwarenessAllocationDecider;
 import org.elasticsearch.common.Priority;
 import org.elasticsearch.common.settings.Settings;
@@ -327,9 +327,10 @@ Map<String, Integer> computeShardCounts(ClusterState clusterState) {
         Map<String, Integer> counts = new HashMap<>();
 
         for (IndexRoutingTable indexRoutingTable : clusterState.routingTable()) {
-            for (int i = 0; i < indexRoutingTable.size(); i++) {
-                for (ShardRouting shardRouting : indexRoutingTable.shard(i)) {
-                    counts.merge(clusterState.nodes().get(shardRouting.currentNodeId()).getName(), 1, Integer::sum);
+            for (int shardId = 0; shardId < indexRoutingTable.size(); shardId++) {
+                final IndexShardRoutingTable indexShardRoutingTable = indexRoutingTable.shard(shardId);
+                for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+                    counts.merge(clusterState.nodes().get(indexShardRoutingTable.shard(copy).currentNodeId()).getName(), 1, Integer::sum);
                 }
             }
         }

server/src/internalClusterTest/java/org/elasticsearch/cluster/allocation/FilteringAllocationIT.java

@@ -13,6 +13,7 @@
 import org.elasticsearch.cluster.metadata.AutoExpandReplicas;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.cluster.routing.IndexRoutingTable;
+import org.elasticsearch.cluster.routing.IndexShardRoutingTable;
 import org.elasticsearch.cluster.routing.RoutingNodesHelper;
 import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.cluster.routing.ShardRoutingState;
@@ -79,9 +80,10 @@ public void testDecommissionNodeNoReplicas() {
         logger.info("--> verify all are allocated on node1 now");
         ClusterState clusterState = client().admin().cluster().prepareState().execute().actionGet().getState();
         for (IndexRoutingTable indexRoutingTable : clusterState.routingTable()) {
-            for (int i = 0; i < indexRoutingTable.size(); i++) {
-                for (ShardRouting shardRouting : indexRoutingTable.shard(i)) {
-                    assertThat(clusterState.nodes().get(shardRouting.currentNodeId()).getName(), equalTo(node_0));
+            for (int shardId = 0; shardId < indexRoutingTable.size(); shardId++) {
+                final IndexShardRoutingTable indexShardRoutingTable = indexRoutingTable.shard(shardId);
+                for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+                    assertThat(clusterState.nodes().get(indexShardRoutingTable.shard(copy).currentNodeId()).getName(), equalTo(node_0));
                 }
             }
         }
@@ -138,9 +140,10 @@ public void testAutoExpandReplicasToFilteredNodes() {
         clusterState = client().admin().cluster().prepareState().execute().actionGet().getState();
         assertThat(clusterState.metadata().index("test").getNumberOfReplicas(), equalTo(0));
         for (IndexRoutingTable indexRoutingTable : clusterState.routingTable()) {
-            for (int i = 0; i < indexRoutingTable.size(); i++) {
-                for (ShardRouting shardRouting : indexRoutingTable.shard(i)) {
-                    assertThat(clusterState.nodes().get(shardRouting.currentNodeId()).getName(), equalTo(node_0));
+            for (int shardId = 0; shardId < indexRoutingTable.size(); shardId++) {
+                final IndexShardRoutingTable indexShardRoutingTable = indexRoutingTable.shard(shardId);
+                for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+                    assertThat(clusterState.nodes().get(indexShardRoutingTable.shard(copy).currentNodeId()).getName(), equalTo(node_0));
                 }
             }
         }
@@ -185,9 +188,10 @@ public void testDisablingAllocationFiltering() {
         ClusterState clusterState = client().admin().cluster().prepareState().execute().actionGet().getState();
         IndexRoutingTable indexRoutingTable = clusterState.routingTable().index("test");
         int numShardsOnNode1 = 0;
-        for (int i = 0; i < indexRoutingTable.size(); i++) {
-            for (ShardRouting shardRouting : indexRoutingTable.shard(i)) {
-                if ("node1".equals(clusterState.nodes().get(shardRouting.currentNodeId()).getName())) {
+        for (int shardId = 0; shardId < indexRoutingTable.size(); shardId++) {
+            final IndexShardRoutingTable indexShardRoutingTable = indexRoutingTable.shard(shardId);
+            for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+                if ("node1".equals(clusterState.nodes().get(indexShardRoutingTable.shard(copy).currentNodeId()).getName())) {
                     numShardsOnNode1++;
                 }
             }
@@ -216,9 +220,10 @@ public void testDisablingAllocationFiltering() {
         logger.info("--> verify all shards are allocated on node_1 now");
         clusterState = client().admin().cluster().prepareState().execute().actionGet().getState();
         indexRoutingTable = clusterState.routingTable().index("test");
-        for (int i = 0; i < indexRoutingTable.size(); i++) {
-            for (ShardRouting shardRouting : indexRoutingTable.shard(i)) {
-                assertThat(clusterState.nodes().get(shardRouting.currentNodeId()).getName(), equalTo(node_1));
+        for (int shardId = 0; shardId < indexRoutingTable.size(); shardId++) {
+            final IndexShardRoutingTable indexShardRoutingTable = indexRoutingTable.shard(shardId);
+            for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+                assertThat(clusterState.nodes().get(indexShardRoutingTable.shard(copy).currentNodeId()).getName(), equalTo(node_1));
             }
         }
 

server/src/internalClusterTest/java/org/elasticsearch/cluster/routing/allocation/decider/DiskThresholdDeciderIT.java

@@ -18,6 +18,7 @@
 import org.elasticsearch.cluster.InternalClusterInfoService;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.cluster.routing.IndexRoutingTable;
+import org.elasticsearch.cluster.routing.IndexShardRoutingTable;
 import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.cluster.routing.ShardRoutingState;
 import org.elasticsearch.cluster.routing.allocation.DiskThresholdSettings;
@@ -196,8 +197,10 @@ private Set<ShardRouting> getShardRoutings(final String nodeId, final String ind
             .getState()
             .getRoutingTable()
             .index(indexName);
-        for (int i = 0; i < indexRoutingTable.size(); i++) {
-            for (ShardRouting shard : indexRoutingTable.shard(i).shards()) {
+        for (int shardId = 0; shardId < indexRoutingTable.size(); shardId++) {
+            final IndexShardRoutingTable shardRoutingTable = indexRoutingTable.shard(shardId);
+            for (int copy = 0; copy < shardRoutingTable.size(); copy++) {
+                ShardRouting shard = shardRoutingTable.shard(copy);
                 assertThat(shard.state(), equalTo(ShardRoutingState.STARTED));
                 if (shard.currentNodeId().equals(nodeId)) {
                     shardRoutings.add(shard);

server/src/internalClusterTest/java/org/elasticsearch/gateway/ReplicaShardAllocatorIT.java

@@ -11,6 +11,7 @@
 import org.elasticsearch.action.admin.indices.stats.ShardStats;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.cluster.node.DiscoveryNode;
+import org.elasticsearch.cluster.routing.RoutingNodesHelper;
 import org.elasticsearch.cluster.routing.UnassignedInfo;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.Priority;
@@ -465,12 +466,7 @@ public static void ensureActivePeerRecoveryRetentionLeasesAdvanced(String indexN
         final ClusterService clusterService = internalCluster().clusterService();
         assertBusy(() -> {
             Index index = resolveIndex(indexName);
-            Set<String> activeRetentionLeaseIds = clusterService.state()
-                .routingTable()
-                .index(index)
-                .shard(0)
-                .shards()
-                .stream()
+            Set<String> activeRetentionLeaseIds = RoutingNodesHelper.asStream(clusterService.state().routingTable().index(index).shard(0))
                 .map(shardRouting -> ReplicationTracker.getPeerRecoveryRetentionLeaseId(shardRouting.currentNodeId()))
                 .collect(Collectors.toSet());
             for (String node : internalCluster().nodesInclude(indexName)) {

server/src/internalClusterTest/java/org/elasticsearch/index/store/CorruptedFileIT.java

@@ -29,6 +29,7 @@
 import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.cluster.routing.GroupShardsIterator;
 import org.elasticsearch.cluster.routing.IndexRoutingTable;
+import org.elasticsearch.cluster.routing.IndexShardRoutingTable;
 import org.elasticsearch.cluster.routing.ShardIterator;
 import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.cluster.routing.ShardRoutingState;
@@ -498,8 +499,10 @@ public void testCorruptionOnNetworkLayer() throws ExecutionException, Interrupte
         // ensure that no shard is actually allocated on the unlucky node
         ClusterStateResponse clusterStateResponse = client().admin().cluster().prepareState().get();
         final IndexRoutingTable indexRoutingTable = clusterStateResponse.getState().getRoutingTable().index("test");
-        for (int i = 0; i < indexRoutingTable.size(); i++) {
-            for (ShardRouting routing : indexRoutingTable.shard(i)) {
+        for (int shardId = 0; shardId < indexRoutingTable.size(); shardId++) {
+            final IndexShardRoutingTable indexShardRoutingTable = indexRoutingTable.shard(shardId);
+            for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+                final ShardRouting routing = indexShardRoutingTable.shard(copy);
                 if (unluckyNode.getNode().getId().equals(routing.currentNodeId())) {
                     assertThat(routing.state(), not(equalTo(ShardRoutingState.STARTED)));
                     assertThat(routing.state(), not(equalTo(ShardRoutingState.RELOCATING)));

server/src/internalClusterTest/java/org/elasticsearch/recovery/RecoveryWhileUnderLoadIT.java

@@ -16,6 +16,7 @@
 import org.elasticsearch.action.get.GetResponse;
 import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.routing.IndexShardRoutingTable;
 import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.Priority;
@@ -391,7 +392,9 @@ private void iterateAssertCount(final int numberOfShards, final int iterations,
                 for (String id : ids) {
                     ShardId docShard = clusterService.operationRouting().shardId(state, "test", id, null);
                     if (docShard.id() == shard) {
-                        for (ShardRouting shardRouting : state.routingTable().shardRoutingTable("test", shard)) {
+                        final IndexShardRoutingTable indexShardRoutingTable = state.routingTable().shardRoutingTable("test", shard);
+                        for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+                            ShardRouting shardRouting = indexShardRoutingTable.shard(copy);
                             GetResponse response = client().prepareGet("test", id)
                                 .setPreference("_only_nodes:" + shardRouting.currentNodeId())
                                 .get();

server/src/main/java/org/elasticsearch/action/support/replication/ReplicationOperation.java

@@ -383,7 +383,7 @@ protected String checkActiveShardCount() {
             return null;
         } else {
             final String resolvedShards = waitForActiveShards == ActiveShardCount.ALL
-                ? Integer.toString(shardRoutingTable.shards().size())
+                ? Integer.toString(shardRoutingTable.size())
                 : waitForActiveShards.toString();
             logger.trace(
                 "[{}] not enough active copies to meet shard count of [{}] (have {}, needed {}), scheduling a retry. op [{}], "

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

@@ -522,11 +522,11 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
             for (IndexRoutingTable indexRoutingTable : routingTable()) {
                 builder.startObject(indexRoutingTable.getIndex().getName());
                 builder.startObject("shards");
-                for (int i = 0; i < indexRoutingTable.size(); i++) {
-                    IndexShardRoutingTable indexShardRoutingTable = indexRoutingTable.shard(i);
+                for (int shardId = 0; shardId < indexRoutingTable.size(); shardId++) {
+                    IndexShardRoutingTable indexShardRoutingTable = indexRoutingTable.shard(shardId);
                     builder.startArray(Integer.toString(indexShardRoutingTable.shardId().id()));
-                    for (ShardRouting shardRouting : indexShardRoutingTable) {
-                        shardRouting.toXContent(builder, params);
+                    for (int copy = 0; copy < indexShardRoutingTable.size(); copy++) {
+                        indexShardRoutingTable.shard(copy).toXContent(builder, params);
                     }
                     builder.endArray();
                 }

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

@@ -85,7 +85,8 @@ public ClusterShardHealth(final int shardId, final IndexShardRoutingTable shardR
         int computeRelocatingShards = 0;
         int computeInitializingShards = 0;
         int computeUnassignedShards = 0;
-        for (ShardRouting shardRouting : shardRoutingTable) {
+        for (int j = 0; j < shardRoutingTable.size(); j++) {
+            ShardRouting shardRouting = shardRoutingTable.shard(j);
             if (shardRouting.active()) {
                 computeActiveShards++;
                 if (shardRouting.relocating()) {