Add replica to primary promotion test for closed indices (elastic#39110)

This commit adds a simple test which verifies that a replica can be promoted 
as a primary when the index is closed.

Relates to elastic#33888

server/src/test/java/org/elasticsearch/indices/recovery/ReplicaToPrimaryPromotionIT.java

@@ -0,0 +1,87 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.elasticsearch.indices.recovery;
+
+import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.metadata.IndexMetaData;
+import org.elasticsearch.cluster.node.DiscoveryNode;
+import org.elasticsearch.cluster.routing.IndexShardRoutingTable;
+import org.elasticsearch.cluster.routing.ShardRouting;
+import org.elasticsearch.test.BackgroundIndexer;
+import org.elasticsearch.test.ESIntegTestCase;
+import org.elasticsearch.test.InternalTestCluster;
+
+import java.util.Locale;
+
+import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
+import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertHitCount;
+import static org.hamcrest.Matchers.is;
+
+@ESIntegTestCase.ClusterScope(numDataNodes = 2)
+public class ReplicaToPrimaryPromotionIT extends ESIntegTestCase {
+
+    @Override
+    protected int numberOfReplicas() {
+        return 1;
+    }
+
+    public void testPromoteReplicaToPrimary() throws Exception {
+        final String indexName = randomAlphaOfLength(5).toLowerCase(Locale.ROOT);
+        createIndex(indexName);
+
+        final int numOfDocs = scaledRandomIntBetween(0, 200);
+        try (BackgroundIndexer indexer = new BackgroundIndexer(indexName, "_doc", client(), numOfDocs)) {
+            waitForDocs(numOfDocs, indexer);
+        }
+        refresh(indexName);
+
+        assertHitCount(client().prepareSearch(indexName).setSize(0).get(), numOfDocs);
+        ensureGreen(indexName);
+
+        // sometimes test with a closed index
+        final IndexMetaData.State indexState = randomFrom(IndexMetaData.State.OPEN, IndexMetaData.State.CLOSE);
+        if (indexState == IndexMetaData.State.CLOSE) {
+            assertAcked(client().admin().indices().prepareClose(indexName));
+            ensureGreen(indexName);
+        }
+
+        // pick up a data node that contains a random primary shard
+        ClusterState state = client(internalCluster().getMasterName()).admin().cluster().prepareState().get().getState();
+        final int numShards = state.metaData().index(indexName).getNumberOfShards();
+        final ShardRouting primaryShard = state.routingTable().index(indexName).shard(randomIntBetween(0, numShards - 1)).primaryShard();
+        final DiscoveryNode randomNode = state.nodes().resolveNode(primaryShard.currentNodeId());
+
+        // stop the random data node, all remaining shards are promoted to primaries
+        internalCluster().stopRandomNode(InternalTestCluster.nameFilter(randomNode.getName()));
+        ensureYellowAndNoInitializingShards(indexName);
+
+        state = client(internalCluster().getMasterName()).admin().cluster().prepareState().get().getState();
+        for (IndexShardRoutingTable shardRoutingTable : state.routingTable().index(indexName)) {
+            for (ShardRouting shardRouting : shardRoutingTable.activeShards()) {
+                assertThat(shardRouting + " should be promoted as a primary", shardRouting.primary(), is(true));
+            }
+        }
+
+        if (indexState == IndexMetaData.State.CLOSE) {
+            assertAcked(client().admin().indices().prepareOpen(indexName));
+            ensureYellowAndNoInitializingShards(indexName);
+        }
+        assertHitCount(client().prepareSearch(indexName).setSize(0).get(), numOfDocs);
+    }
+}