From 0a99df6e9a3cf1834b19e23bc9f2076358ab94ed Mon Sep 17 00:00:00 2001
From: Nhat Nguyen <nhat.nguyen@elastic.co>
Date: Wed, 9 Sep 2020 15:02:47 -0400
Subject: [PATCH] Do not add unmatched shard routing

---
 .../action/search/TransportSearchAction.java  | 37 ++++---------------
 .../cluster/routing/OperationRouting.java     |  5 ---
 2 files changed, 8 insertions(+), 34 deletions(-)

diff --git a/server/src/main/java/org/elasticsearch/action/search/TransportSearchAction.java b/server/src/main/java/org/elasticsearch/action/search/TransportSearchAction.java
index a5b6cf2fc3643..e41a9c5e7d8a2 100644
--- a/server/src/main/java/org/elasticsearch/action/search/TransportSearchAction.java
+++ b/server/src/main/java/org/elasticsearch/action/search/TransportSearchAction.java
@@ -39,9 +39,7 @@
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
 import org.elasticsearch.cluster.routing.GroupShardsIterator;
-import org.elasticsearch.cluster.routing.OperationRouting;
 import org.elasticsearch.cluster.routing.ShardIterator;
-import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Strings;
@@ -581,14 +579,8 @@ static List<SearchShardIterator> getRemoteShardsIteratorFromPointInTime(Map<Stri
                 final String clusterAlias = entry.getKey();
                 final SearchContextIdForNode perNode = searchContextId.shards().get(shardId);
                 assert clusterAlias.equals(perNode.getClusterAlias()) : clusterAlias + " != " + perNode.getClusterAlias();
-                final List<String> nodeIds = new ArrayList<>();
-                nodeIds.add(perNode.getNode()); // always search with the matching node first
-                for (ShardRouting shard : group.getShards()) {
-                    if (perNode.getNode().equals(shard.currentNodeId()) == false) {
-                        nodeIds.add(shard.currentNodeId());
-                    }
-                }
-                SearchShardIterator shardIterator = new SearchShardIterator(clusterAlias, shardId, nodeIds,
+                final List<String> targetNodes = List.of(perNode.getNode());
+                SearchShardIterator shardIterator = new SearchShardIterator(clusterAlias, shardId, targetNodes,
                     remoteClusterIndices.get(clusterAlias), perNode.getSearchContextId(), searchContextKeepAlive);
                 remoteShardIterators.add(shardIterator);
             }
@@ -627,7 +619,7 @@ private void executeSearch(SearchTask task, SearchTimeProvider timeProvider, Sea
             aliasFilter = searchContext.aliasFilter();
             indexRoutings = Map.of();
             concreteLocalIndices = localIndices == null ? new String[0] : localIndices.indices();
-            localShardIterators = getLocalLocalShardsIteratorFromPointInTime(clusterState, localIndices,
+            localShardIterators = getLocalLocalShardsIteratorFromPointInTime(localIndices,
                 searchRequest.getLocalClusterAlias(), searchContext, searchRequest.pointInTimeBuilder().getKeepAlive());
         } else {
             final Index[] indices = resolveLocalIndices(localIndices, clusterState, timeProvider);
@@ -922,29 +914,16 @@ static Map<String, OriginalIndices> getIndicesFromSearchContexts(SearchContextId
             .collect(Collectors.toMap(Map.Entry::getKey, e -> new OriginalIndices(e.getValue().toArray(String[]::new), indicesOptions)));
     }
 
-    static List<SearchShardIterator> getLocalLocalShardsIteratorFromPointInTime(ClusterState clusterState,
-                                                                                OriginalIndices originalIndices,
-                                                                                String localClusterAlias,
-                                                                                SearchContextId searchContext,
-                                                                                TimeValue keepAlive) {
+    static List<SearchShardIterator> getLocalLocalShardsIteratorFromPointInTime(OriginalIndices originalIndices, String localClusterAlias,
+                                                                                SearchContextId searchContext, TimeValue keepAlive) {
         final List<SearchShardIterator> iterators = new ArrayList<>(searchContext.shards().size());
         for (Map.Entry<ShardId, SearchContextIdForNode> entry : searchContext.shards().entrySet()) {
             final SearchContextIdForNode perNode = entry.getValue();
             if (Strings.isEmpty(perNode.getClusterAlias())) {
                 final ShardId shardId = entry.getKey();
-                final ShardIterator shards = OperationRouting.getShards(clusterState, shardId);
-                final List<String> matchingNodeFirst = new ArrayList<>(shards.size());
-                final String nodeId = perNode.getNode();
-                // always search the matching node first even when its shard was relocated to another node
-                // because the point in time should keep the corresponding search context open.
-                matchingNodeFirst.add(nodeId);
-                for (ShardRouting shard : shards) {
-                    if (shard.currentNodeId().equals(nodeId) == false) {
-                        matchingNodeFirst.add(shard.currentNodeId());
-                    }
-                }
-                iterators.add(new SearchShardIterator(localClusterAlias, shardId, matchingNodeFirst, originalIndices,
-                    perNode.getSearchContextId(), keepAlive));
+                final List<String> targetNodes = List.of(perNode.getNode());
+                iterators.add(new SearchShardIterator(
+                    localClusterAlias, shardId, targetNodes, originalIndices, perNode.getSearchContextId(), keepAlive));
             }
         }
         return iterators;
diff --git a/server/src/main/java/org/elasticsearch/cluster/routing/OperationRouting.java b/server/src/main/java/org/elasticsearch/cluster/routing/OperationRouting.java
index 5a8dfbcc06470..731eab51186a5 100644
--- a/server/src/main/java/org/elasticsearch/cluster/routing/OperationRouting.java
+++ b/server/src/main/java/org/elasticsearch/cluster/routing/OperationRouting.java
@@ -98,11 +98,6 @@ public GroupShardsIterator<ShardIterator> searchShards(ClusterState clusterState
         return GroupShardsIterator.sortAndCreate(new ArrayList<>(set));
     }
 
-    public static ShardIterator getShards(ClusterState clusterState, ShardId shardId) {
-        final IndexShardRoutingTable shard = clusterState.routingTable().shardRoutingTable(shardId);
-        return shard.activeInitializingShardsRandomIt();
-    }
-
     private static final Map<String, Set<String>> EMPTY_ROUTING = Collections.emptyMap();
 
     private Set<IndexShardRoutingTable> computeTargetedShards(ClusterState clusterState, String[] concreteIndices,