Revert fast refresh using search shards

server/src/main/java/org/elasticsearch/action/admin/indices/refresh/TransportShardRefreshAction.java

@@ -23,6 +23,7 @@
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.shard.IndexShard;
 import org.elasticsearch.indices.IndicesService;
 import org.elasticsearch.injection.guice.Inject;
@@ -119,18 +120,27 @@ public void onPrimaryOperationComplete(
             ActionListener<Void> listener
         ) {
             assert replicaRequest.primaryRefreshResult.refreshed() : "primary has not refreshed";
-            UnpromotableShardRefreshRequest unpromotableReplicaRequest = new UnpromotableShardRefreshRequest(
-                indexShardRoutingTable,
-                replicaRequest.primaryRefreshResult.primaryTerm(),
-                replicaRequest.primaryRefreshResult.generation(),
-                false
-            );
-            transportService.sendRequest(
-                transportService.getLocalNode(),
-                TransportUnpromotableShardRefreshAction.NAME,
-                unpromotableReplicaRequest,
-                new ActionListenerResponseHandler<>(listener.safeMap(r -> null), in -> ActionResponse.Empty.INSTANCE, refreshExecutor)
+            boolean fastRefresh = IndexSettings.INDEX_FAST_REFRESH_SETTING.get(
+                clusterService.state().metadata().index(indexShardRoutingTable.shardId().getIndex()).getSettings()
             );
+
+            // Indices marked with fast refresh do not rely on refreshing the unpromotables
+            if (fastRefresh) {
+                listener.onResponse(null);
+            } else {
+                UnpromotableShardRefreshRequest unpromotableReplicaRequest = new UnpromotableShardRefreshRequest(
+                    indexShardRoutingTable,
+                    replicaRequest.primaryRefreshResult.primaryTerm(),
+                    replicaRequest.primaryRefreshResult.generation(),
+                    false
+                );
+                transportService.sendRequest(
+                    transportService.getLocalNode(),
+                    TransportUnpromotableShardRefreshAction.NAME,
+                    unpromotableReplicaRequest,
+                    new ActionListenerResponseHandler<>(listener.safeMap(r -> null), in -> ActionResponse.Empty.INSTANCE, refreshExecutor)
+                );
+            }
         }
     }
 }

server/src/main/java/org/elasticsearch/action/admin/indices/refresh/TransportUnpromotableShardRefreshAction.java

@@ -24,9 +24,6 @@
 
 import java.util.List;
 
-import static org.elasticsearch.TransportVersions.FAST_REFRESH_RCO;
-import static org.elasticsearch.index.IndexSettings.INDEX_FAST_REFRESH_SETTING;
-
 public class TransportUnpromotableShardRefreshAction extends TransportBroadcastUnpromotableAction<
     UnpromotableShardRefreshRequest,
     ActionResponse.Empty> {
@@ -76,18 +73,6 @@ protected void unpromotableShardOperation(
             return;
         }
 
-        // During an upgrade to FAST_REFRESH_RCO, we expect search shards to be first upgraded before the primary is upgraded. Thus,
-        // when the primary is upgraded, and starts to deliver unpromotable refreshes, we expect the search shards to be upgraded already.
-        // Note that the fast refresh setting is final.
-        // TODO: remove assertion (ES-9563)
-        assert INDEX_FAST_REFRESH_SETTING.get(shard.indexSettings().getSettings()) == false
-            || transportService.getLocalNodeConnection().getTransportVersion().onOrAfter(FAST_REFRESH_RCO)
-            : "attempted to refresh a fast refresh search shard "
-                + shard
-                + " on transport version "
-                + transportService.getLocalNodeConnection().getTransportVersion()
-                + " (before FAST_REFRESH_RCO)";
-
         ActionListener.run(responseListener, listener -> {
             shard.waitForPrimaryTermAndGeneration(
                 request.getPrimaryTerm(),

server/src/main/java/org/elasticsearch/action/get/TransportGetAction.java

@@ -126,10 +126,11 @@ protected void asyncShardOperation(GetRequest request, ShardId shardId, ActionLi
         IndexService indexService = indicesService.indexServiceSafe(shardId.getIndex());
         IndexShard indexShard = indexService.getShard(shardId.id());
         if (indexShard.routingEntry().isPromotableToPrimary() == false) {
+            assert indexShard.indexSettings().isFastRefresh() == false
+                : "a search shard should not receive a TransportGetAction for an index with fast refresh";
             handleGetOnUnpromotableShard(request, indexShard, listener);
             return;
         }
-        // TODO: adapt assertion to assert only that it is not stateless (ES-9563)
         assert DiscoveryNode.isStateless(clusterService.getSettings()) == false || indexShard.indexSettings().isFastRefresh()
             : "in Stateless a promotable to primary shard can receive a TransportGetAction only if an index has the fast refresh setting";
         if (request.realtime()) { // we are not tied to a refresh cycle here anyway

server/src/main/java/org/elasticsearch/action/get/TransportShardMultiGetAction.java

@@ -124,10 +124,11 @@ protected void asyncShardOperation(MultiGetShardRequest request, ShardId shardId
         IndexService indexService = indicesService.indexServiceSafe(shardId.getIndex());
         IndexShard indexShard = indexService.getShard(shardId.id());
         if (indexShard.routingEntry().isPromotableToPrimary() == false) {
+            assert indexShard.indexSettings().isFastRefresh() == false
+                : "a search shard should not receive a TransportShardMultiGetAction for an index with fast refresh";
             handleMultiGetOnUnpromotableShard(request, indexShard, listener);
             return;
         }
-        // TODO: adapt assertion to assert only that it is not stateless (ES-9563)
         assert DiscoveryNode.isStateless(clusterService.getSettings()) == false || indexShard.indexSettings().isFastRefresh()
             : "in Stateless a promotable to primary shard can receive a TransportShardMultiGetAction only if an index has "
                 + "the fast refresh setting";

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

@@ -19,6 +19,7 @@
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.TimeValue;
+import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.engine.Engine;
 import org.elasticsearch.index.shard.IndexShard;
 import org.elasticsearch.index.translog.Translog;
@@ -52,7 +53,9 @@ public void refreshShard(
             case WAIT_UNTIL -> waitUntil(indexShard, location, new ActionListener<>() {
                 @Override
                 public void onResponse(Boolean forced) {
-                    if (location != null && indexShard.routingEntry().isSearchable() == false) {
+                    // Fast refresh indices do not depend on the unpromotables being refreshed
+                    boolean fastRefresh = IndexSettings.INDEX_FAST_REFRESH_SETTING.get(indexShard.indexSettings().getSettings());
+                    if (location != null && (indexShard.routingEntry().isSearchable() == false && fastRefresh == false)) {
                         refreshUnpromotables(indexShard, location, listener, forced, postWriteRefreshTimeout);
                     } else {
                         listener.onResponse(forced);
@@ -65,7 +68,9 @@ public void onFailure(Exception e) {
                 }
             });
             case IMMEDIATE -> immediate(indexShard, listener.delegateFailureAndWrap((l, r) -> {
-                if (indexShard.getReplicationGroup().getRoutingTable().unpromotableShards().size() > 0) {
+                // Fast refresh indices do not depend on the unpromotables being refreshed
+                boolean fastRefresh = IndexSettings.INDEX_FAST_REFRESH_SETTING.get(indexShard.indexSettings().getSettings());
+                if (indexShard.getReplicationGroup().getRoutingTable().unpromotableShards().size() > 0 && fastRefresh == false) {
                     sendUnpromotableRequests(indexShard, r.generation(), true, l, postWriteRefreshTimeout);
                 } else {
                     l.onResponse(true);

server/src/main/java/org/elasticsearch/cluster/routing/OperationRouting.java

@@ -32,7 +32,6 @@
 import java.util.Set;
 import java.util.stream.Collectors;
 
-import static org.elasticsearch.TransportVersions.FAST_REFRESH_RCO;
 import static org.elasticsearch.index.IndexSettings.INDEX_FAST_REFRESH_SETTING;
 
 public class OperationRouting {
@@ -306,14 +305,8 @@ public ShardId shardId(ClusterState clusterState, String index, String id, @Null
     }
 
     public static boolean canSearchShard(ShardRouting shardRouting, ClusterState clusterState) {
-        // TODO: remove if and always return isSearchable (ES-9563)
         if (INDEX_FAST_REFRESH_SETTING.get(clusterState.metadata().index(shardRouting.index()).getSettings())) {
-            // Until all the cluster is upgraded, we send searches/gets to the primary (even if it has been upgraded) to execute locally.
-            if (clusterState.getMinTransportVersion().onOrAfter(FAST_REFRESH_RCO)) {
-                return shardRouting.isSearchable();
-            } else {
-                return shardRouting.isPromotableToPrimary();
-            }
+            return shardRouting.isPromotableToPrimary();
         } else {
             return shardRouting.isSearchable();
         }

server/src/main/java/org/elasticsearch/index/cache/bitset/BitsetFilterCache.java

@@ -58,6 +58,8 @@
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
 
+import static org.elasticsearch.index.IndexSettings.INDEX_FAST_REFRESH_SETTING;
+
 /**
  * This is a cache for {@link BitDocIdSet} based filters and is unbounded by size or time.
  * <p>
@@ -103,7 +105,10 @@ static boolean shouldLoadRandomAccessFiltersEagerly(IndexSettings settings) {
         boolean loadFiltersEagerlySetting = settings.getValue(INDEX_LOAD_RANDOM_ACCESS_FILTERS_EAGERLY_SETTING);
         boolean isStateless = DiscoveryNode.isStateless(settings.getNodeSettings());
         if (isStateless) {
-            return loadFiltersEagerlySetting && DiscoveryNode.hasRole(settings.getNodeSettings(), DiscoveryNodeRole.SEARCH_ROLE);
+            return loadFiltersEagerlySetting
+                && (DiscoveryNode.hasRole(settings.getNodeSettings(), DiscoveryNodeRole.SEARCH_ROLE)
+                    || (DiscoveryNode.hasRole(settings.getNodeSettings(), DiscoveryNodeRole.INDEX_ROLE)
+                        && INDEX_FAST_REFRESH_SETTING.get(settings.getSettings())));
         } else {
             return loadFiltersEagerlySetting;
         }

server/src/test/java/org/elasticsearch/cluster/routing/IndexRoutingTableTests.java

@@ -9,7 +9,6 @@
 
 package org.elasticsearch.cluster.routing;
 
-import org.elasticsearch.TransportVersion;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.common.UUIDs;
 import org.elasticsearch.common.settings.Settings;
@@ -20,7 +19,6 @@
 
 import java.util.List;
 
-import static org.elasticsearch.TransportVersions.FAST_REFRESH_RCO;
 import static org.elasticsearch.index.IndexSettings.INDEX_FAST_REFRESH_SETTING;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.mock;
@@ -29,22 +27,16 @@
 public class IndexRoutingTableTests extends ESTestCase {
 
     public void testReadyForSearch() {
-        innerReadyForSearch(false, false);
-        innerReadyForSearch(false, true);
-        innerReadyForSearch(true, false);
-        innerReadyForSearch(true, true);
+        innerReadyForSearch(false);
+        innerReadyForSearch(true);
     }
 
-    // TODO: remove if (fastRefresh && beforeFastRefreshRCO) branches (ES-9563)
-    private void innerReadyForSearch(boolean fastRefresh, boolean beforeFastRefreshRCO) {
+    private void innerReadyForSearch(boolean fastRefresh) {
         Index index = new Index(randomIdentifier(), UUIDs.randomBase64UUID());
         ClusterState clusterState = mock(ClusterState.class, Mockito.RETURNS_DEEP_STUBS);
         when(clusterState.metadata().index(any(Index.class)).getSettings()).thenReturn(
             Settings.builder().put(INDEX_FAST_REFRESH_SETTING.getKey(), fastRefresh).build()
         );
-        when(clusterState.getMinTransportVersion()).thenReturn(
-            beforeFastRefreshRCO ? TransportVersion.fromId(FAST_REFRESH_RCO.id() - 1_00_0) : TransportVersion.current()
-        );
         // 2 primaries that are search and index
         ShardId p1 = new ShardId(index, 0);
         IndexShardRoutingTable shardTable1 = new IndexShardRoutingTable(
@@ -63,7 +55,7 @@ private void innerReadyForSearch(boolean fastRefresh, boolean beforeFastRefreshR
         shardTable1 = new IndexShardRoutingTable(p1, List.of(getShard(p1, true, ShardRoutingState.STARTED, ShardRouting.Role.INDEX_ONLY)));
         shardTable2 = new IndexShardRoutingTable(p2, List.of(getShard(p2, true, ShardRoutingState.STARTED, ShardRouting.Role.INDEX_ONLY)));
         indexRoutingTable = new IndexRoutingTable(index, new IndexShardRoutingTable[] { shardTable1, shardTable2 });
-        if (fastRefresh && beforeFastRefreshRCO) {
+        if (fastRefresh) {
             assertTrue(indexRoutingTable.readyForSearch(clusterState));
         } else {
             assertFalse(indexRoutingTable.readyForSearch(clusterState));
@@ -99,7 +91,7 @@ private void innerReadyForSearch(boolean fastRefresh, boolean beforeFastRefreshR
             )
         );
         indexRoutingTable = new IndexRoutingTable(index, new IndexShardRoutingTable[] { shardTable1, shardTable2 });
-        if (fastRefresh && beforeFastRefreshRCO) {
+        if (fastRefresh) {
             assertTrue(indexRoutingTable.readyForSearch(clusterState));
         } else {
             assertFalse(indexRoutingTable.readyForSearch(clusterState));
@@ -126,6 +118,8 @@ private void innerReadyForSearch(boolean fastRefresh, boolean beforeFastRefreshR
         assertTrue(indexRoutingTable.readyForSearch(clusterState));
 
         // 2 unassigned primaries that are index only with some replicas that are all available
+        // Fast refresh indices do not support replicas so this can not practically happen. If we add support we will want to ensure
+        // that readyForSearch allows for searching replicas when the index shard is not available.
         shardTable1 = new IndexShardRoutingTable(
             p1,
             List.of(
@@ -143,8 +137,8 @@ private void innerReadyForSearch(boolean fastRefresh, boolean beforeFastRefreshR
             )
         );
         indexRoutingTable = new IndexRoutingTable(index, new IndexShardRoutingTable[] { shardTable1, shardTable2 });
-        if (fastRefresh && beforeFastRefreshRCO) {
-            assertFalse(indexRoutingTable.readyForSearch(clusterState));
+        if (fastRefresh) {
+            assertFalse(indexRoutingTable.readyForSearch(clusterState)); // if we support replicas for fast refreshes this needs to change
         } else {
             assertTrue(indexRoutingTable.readyForSearch(clusterState));
         }

server/src/test/java/org/elasticsearch/index/cache/bitset/BitSetFilterCacheTests.java

@@ -48,6 +48,7 @@
 import java.util.concurrent.atomic.AtomicLong;
 
 import static org.elasticsearch.cluster.node.DiscoveryNode.STATELESS_ENABLED_SETTING_NAME;
+import static org.elasticsearch.index.IndexSettings.INDEX_FAST_REFRESH_SETTING;
 import static org.elasticsearch.index.cache.bitset.BitsetFilterCache.INDEX_LOAD_RANDOM_ACCESS_FILTERS_EAGERLY_SETTING;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
@@ -272,21 +273,35 @@ public void testShouldLoadRandomAccessFiltersEagerly() {
         for (var hasIndexRole : values) {
             for (var loadFiltersEagerly : values) {
                 for (var isStateless : values) {
-                    boolean result = BitsetFilterCache.shouldLoadRandomAccessFiltersEagerly(
-                        bitsetFilterCacheSettings(isStateless, hasIndexRole, loadFiltersEagerly)
-                    );
-                    if (isStateless) {
-                        assertEquals(loadFiltersEagerly && hasIndexRole == false, result);
-                    } else {
-                        assertEquals(loadFiltersEagerly, result);
+                    for (var fastRefresh : values) {
+                        if (isStateless == false && fastRefresh) {
+                            // fast refresh is only relevant for stateless indices
+                            continue;
+                        }
+
+                        boolean result = BitsetFilterCache.shouldLoadRandomAccessFiltersEagerly(
+                            bitsetFilterCacheSettings(isStateless, hasIndexRole, loadFiltersEagerly, fastRefresh)
+                        );
+                        if (isStateless) {
+                            assertEquals(loadFiltersEagerly && ((hasIndexRole && fastRefresh) || hasIndexRole == false), result);
+                        } else {
+                            assertEquals(loadFiltersEagerly, result);
+                        }
                     }
                 }
             }
         }
     }
 
-    private IndexSettings bitsetFilterCacheSettings(boolean isStateless, boolean hasIndexRole, boolean loadFiltersEagerly) {
-        var indexSettingsBuilder = Settings.builder().put(INDEX_LOAD_RANDOM_ACCESS_FILTERS_EAGERLY_SETTING.getKey(), loadFiltersEagerly);
+    private IndexSettings bitsetFilterCacheSettings(
+        boolean isStateless,
+        boolean hasIndexRole,
+        boolean loadFiltersEagerly,
+        boolean fastRefresh
+    ) {
+        var indexSettingsBuilder = Settings.builder()
+            .put(INDEX_LOAD_RANDOM_ACCESS_FILTERS_EAGERLY_SETTING.getKey(), loadFiltersEagerly)
+            .put(INDEX_FAST_REFRESH_SETTING.getKey(), fastRefresh);
 
         var nodeSettingsBuilder = Settings.builder()
             .putList(