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 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

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 * ownership. Elasticsearch licenses this file to you under
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 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
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 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
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 * KIND, either express or implied.  See the License for the
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/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.cluster.routing.allocation;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.opensearch.Version;
import org.opensearch.cluster.ClusterState;
import org.opensearch.cluster.OpenSearchAllocationTestCase;
import org.opensearch.cluster.metadata.IndexMetadata;
import org.opensearch.cluster.metadata.Metadata;
import org.opensearch.cluster.node.DiscoveryNodes;
import org.opensearch.cluster.routing.RoutingTable;
import org.opensearch.cluster.routing.allocation.decider.ThrottlingAllocationDecider;
import org.opensearch.common.settings.Settings;

import static org.opensearch.cluster.routing.ShardRoutingState.INITIALIZING;
import static org.opensearch.cluster.routing.ShardRoutingState.RELOCATING;
import static org.opensearch.cluster.routing.ShardRoutingState.STARTED;
import static org.opensearch.cluster.routing.ShardRoutingState.UNASSIGNED;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.nullValue;

public class ConcurrentRebalanceRoutingTests extends OpenSearchAllocationTestCase {
    private final Logger logger = LogManager.getLogger(ConcurrentRebalanceRoutingTests.class);

    public void testClusterConcurrentRebalance() {
        AllocationService strategy = createAllocationService(
            Settings.builder()
                .put("cluster.routing.allocation.node_concurrent_recoveries", 10)
                .put(ThrottlingAllocationDecider.CLUSTER_ROUTING_ALLOCATION_NODE_INITIAL_REPLICAS_RECOVERIES_SETTING.getKey(), 10)
                .put("cluster.routing.allocation.cluster_concurrent_rebalance", 3)
                .build()
        );

        logger.info("Building initial routing table");

        Metadata metadata = Metadata.builder()
            .put(IndexMetadata.builder("test").settings(settings(Version.CURRENT)).numberOfShards(5).numberOfReplicas(1))
            .build();

        RoutingTable initialRoutingTable = RoutingTable.builder().addAsNew(metadata.index("test")).build();

        ClusterState clusterState = ClusterState.builder(org.opensearch.cluster.ClusterName.CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY))
            .metadata(metadata)
            .routingTable(initialRoutingTable)
            .build();

        assertThat(clusterState.routingTable().index("test").shards().size(), equalTo(5));
        for (int i = 0; i < clusterState.routingTable().index("test").shards().size(); i++) {
            assertThat(clusterState.routingTable().index("test").shard(i).shards().size(), equalTo(2));
            assertThat(clusterState.routingTable().index("test").shard(i).shards().get(0).state(), equalTo(UNASSIGNED));
            assertThat(clusterState.routingTable().index("test").shard(i).shards().get(1).state(), equalTo(UNASSIGNED));
            assertThat(clusterState.routingTable().index("test").shard(i).shards().get(0).currentNodeId(), nullValue());
            assertThat(clusterState.routingTable().index("test").shard(i).shards().get(1).currentNodeId(), nullValue());
        }

        logger.info("start two nodes and fully start the shards");
        clusterState = ClusterState.builder(clusterState)
            .nodes(DiscoveryNodes.builder().add(newNode("node1")).add(newNode("node2")))
            .build();
        clusterState = strategy.reroute(clusterState, "reroute");

        for (int i = 0; i < clusterState.routingTable().index("test").shards().size(); i++) {
            assertThat(clusterState.routingTable().index("test").shard(i).shards().size(), equalTo(2));
            assertThat(clusterState.routingTable().index("test").shard(i).primaryShard().state(), equalTo(INITIALIZING));
            assertThat(clusterState.routingTable().index("test").shard(i).replicaShards().get(0).state(), equalTo(UNASSIGNED));
        }

        logger.info("start all the primary shards, replicas will start initializing");
        clusterState = startInitializingShardsAndReroute(strategy, clusterState);

        for (int i = 0; i < clusterState.routingTable().index("test").shards().size(); i++) {
            assertThat(clusterState.routingTable().index("test").shard(i).shards().size(), equalTo(2));
            assertThat(clusterState.routingTable().index("test").shard(i).primaryShard().state(), equalTo(STARTED));
            assertThat(clusterState.routingTable().index("test").shard(i).replicaShards().get(0).state(), equalTo(INITIALIZING));
        }

        logger.info("now, start 8 more nodes, and check that no rebalancing/relocation have happened");
        clusterState = ClusterState.builder(clusterState)
            .nodes(
                DiscoveryNodes.builder(clusterState.nodes())
                    .add(newNode("node3"))
                    .add(newNode("node4"))
                    .add(newNode("node5"))
                    .add(newNode("node6"))
                    .add(newNode("node7"))
                    .add(newNode("node8"))
                    .add(newNode("node9"))
                    .add(newNode("node10"))
            )
            .build();
        clusterState = strategy.reroute(clusterState, "reroute");

        for (int i = 0; i < clusterState.routingTable().index("test").shards().size(); i++) {
            assertThat(clusterState.routingTable().index("test").shard(i).shards().size(), equalTo(2));
            assertThat(clusterState.routingTable().index("test").shard(i).primaryShard().state(), equalTo(STARTED));
            assertThat(clusterState.routingTable().index("test").shard(i).replicaShards().get(0).state(), equalTo(INITIALIZING));
        }

        logger.info("start the replica shards, rebalancing should start, but, only 3 should be rebalancing");
        clusterState = startInitializingShardsAndReroute(strategy, clusterState);

        // we only allow one relocation at a time
        assertThat(clusterState.routingTable().shardsWithState(STARTED).size(), equalTo(7));
        assertThat(clusterState.routingTable().shardsWithState(RELOCATING).size(), equalTo(3));

        logger.info("finalize this session relocation, 3 more should relocate now");
        clusterState = startInitializingShardsAndReroute(strategy, clusterState);

        // we only allow one relocation at a time
        assertThat(clusterState.routingTable().shardsWithState(STARTED).size(), equalTo(7));
        assertThat(clusterState.routingTable().shardsWithState(RELOCATING).size(), equalTo(3));

        logger.info("finalize this session relocation, 2 more should relocate now");
        clusterState = startInitializingShardsAndReroute(strategy, clusterState);

        // we only allow one relocation at a time
        assertThat(clusterState.routingTable().shardsWithState(STARTED).size(), equalTo(8));
        assertThat(clusterState.routingTable().shardsWithState(RELOCATING).size(), equalTo(2));

        logger.info("finalize this session relocation, no more relocation");
        clusterState = startInitializingShardsAndReroute(strategy, clusterState);

        // we only allow one relocation at a time
        assertThat(clusterState.routingTable().shardsWithState(STARTED).size(), equalTo(10));
        assertThat(clusterState.routingTable().shardsWithState(RELOCATING).size(), equalTo(0));
    }
}