Fix closed-index reroute handling

CHANGELOG.md

@@ -53,6 +53,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Service does not start on Windows with OpenJDK ([#20615](https://github.com/opensearch-project/OpenSearch/pull/20615))
 - Update RemoteClusterStateCleanupManager to performed batched deletions of stale ClusterMetadataManifests and address deletion timeout issues ([#20566](https://github.com/opensearch-project/OpenSearch/pull/20566))
 - Fix the regression of terms agg optimization at high cardinality ([#20623](https://github.com/opensearch-project/OpenSearch/pull/20623))
+- Fix Shard routings for closed index are allocated again without opening the index ([#20648](https://github.com/opensearch-project/OpenSearch/pull/20648))
 - Leveraging segment-global ordinal mapping for efficient terms aggregation ([#20624](https://github.com/opensearch-project/OpenSearch/pull/20624))
 - Support Docker distribution builds for ppc64le, arm64 and s390x ([#20678](https://github.com/opensearch-project/OpenSearch/pull/20678))
 - Harden detection of HTTP/3 support by ensuring Quic native libraries are available for the target platform ([#20680](https://github.com/opensearch-project/OpenSearch/pull/20680))

server/src/main/java/org/opensearch/cluster/routing/ShardRouting.java

@@ -956,4 +956,11 @@ public boolean unassignedReasonIndexCreated() {
         }
         return false;
     }
+
+    public boolean isClosedIndexShard() {
+        if (unassigned() && unassignedInfo != null) {
+            return unassignedInfo.getReason() == UnassignedInfo.Reason.INDEX_CLOSED;
+        }
+        return false;
+    }
 }

server/src/main/java/org/opensearch/gateway/GatewayAllocator.java

@@ -180,6 +180,10 @@ protected static void innerAllocatedUnassigned(
         ExistingShardsAllocator.UnassignedAllocationHandler unassignedAllocationHandler
     ) {
         assert shardRouting.unassigned();
+        // Skip allocation for closed index shards
+        if (shardRouting.isClosedIndexShard()) {
+            return;
+        }
         if (shardRouting.primary()) {
             primaryShardAllocator.allocateUnassigned(shardRouting, allocation, unassignedAllocationHandler);
         } else {

server/src/main/java/org/opensearch/gateway/ShardsBatchGatewayAllocator.java

@@ -401,6 +401,10 @@ protected Set<String> createAndUpdateBatches(RoutingAllocation allocation, boole
         Set<ShardId> batchedShardsToAssign = Sets.newHashSet();
         // add all unassigned shards to the batch if they are not already in a batch
         unassigned.forEach(shardRouting -> {
+            // Skip allocation for closed index shards - for new shards and already-batched shards whose index subsequently closed
+            if (shardRouting.isClosedIndexShard()) {
+                return;
+            }
             if ((currentBatchedShards.containsKey(shardRouting.shardId()) == false) && (shardRouting.primary() == primary)) {
                 assert shardRouting.unassigned();
                 newShardsToBatch.put(shardRouting.shardId(), shardRouting);

server/src/test/java/org/opensearch/cluster/routing/ShardRoutingTests.java

@@ -313,6 +313,44 @@ public void testSwapPrimaryWithReplica() {
         assertFalse(activeReplicaShard1.primary());
     }
 
+    public void testIsClosedIndexShard() {
+        ShardRouting closedShard = TestShardRouting.newShardRouting(
+            "test",
+            0,
+            null,
+            null,
+            false,
+            ShardRoutingState.UNASSIGNED,
+            new UnassignedInfo(UnassignedInfo.Reason.INDEX_CLOSED, "index closed")
+        );
+        assertTrue(closedShard.isClosedIndexShard());
+
+        ShardRouting createdShard = TestShardRouting.newShardRouting(
+            "test",
+            0,
+            null,
+            null,
+            false,
+            ShardRoutingState.UNASSIGNED,
+            new UnassignedInfo(UnassignedInfo.Reason.INDEX_CREATED, "index created")
+        );
+        assertFalse(createdShard.isClosedIndexShard());
+
+        ShardRouting startedShard = TestShardRouting.newShardRouting("test", 0, "node1", true, ShardRoutingState.STARTED);
+        assertFalse(startedShard.isClosedIndexShard());
+
+        ShardRouting initializingShard = TestShardRouting.newShardRouting(
+            "test",
+            0,
+            "node1",
+            null,
+            false,
+            ShardRoutingState.INITIALIZING,
+            new UnassignedInfo(UnassignedInfo.Reason.INDEX_CLOSED, "index closed")
+        );
+        assertFalse(initializingShard.isClosedIndexShard());
+    }
+
     public void testExpectedSize() throws IOException {
         final int iters = randomIntBetween(10, 100);
         for (int i = 0; i < iters; i++) {