/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.apache.solr.cloud.api.collections;


import java.lang.invoke.MethodHandles;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.solr.client.solrj.cloud.DistribStateManager;
import org.apache.solr.client.solrj.cloud.DistributedQueue;
import org.apache.solr.client.solrj.cloud.NodeStateProvider;
import org.apache.solr.client.solrj.cloud.SolrCloudManager;
import org.apache.solr.client.solrj.cloud.autoscaling.PolicyHelper;
import org.apache.solr.client.solrj.cloud.autoscaling.ReplicaInfo;
import org.apache.solr.client.solrj.cloud.autoscaling.Variable.Type;
import org.apache.solr.client.solrj.cloud.autoscaling.VersionedData;
import org.apache.solr.client.solrj.request.CoreAdminRequest;
import org.apache.solr.cloud.Overseer;
import org.apache.solr.cloud.overseer.OverseerAction;
import org.apache.solr.common.SolrException;
import org.apache.solr.common.cloud.ClusterState;
import org.apache.solr.common.cloud.CompositeIdRouter;
import org.apache.solr.common.cloud.DocCollection;
import org.apache.solr.common.cloud.DocRouter;
import org.apache.solr.common.cloud.PlainIdRouter;
import org.apache.solr.common.cloud.Replica;
import org.apache.solr.common.cloud.ReplicaPosition;
import org.apache.solr.common.cloud.Slice;
import org.apache.solr.common.cloud.ZkNodeProps;
import org.apache.solr.common.cloud.ZkStateReader;
import org.apache.solr.common.cloud.rule.ImplicitSnitch;
import org.apache.solr.common.params.CommonAdminParams;
import org.apache.solr.common.params.CommonParams;
import org.apache.solr.common.params.CoreAdminParams;
import org.apache.solr.common.params.ModifiableSolrParams;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.common.util.Utils;
import org.apache.solr.handler.component.ShardHandler;
import org.apache.solr.update.SolrIndexSplitter;
import org.apache.solr.util.RTimerTree;
import org.apache.solr.util.TestInjection;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.data.Stat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static org.apache.solr.common.cloud.ZkStateReader.COLLECTION_PROP;
import static org.apache.solr.common.cloud.ZkStateReader.REPLICA_TYPE;
import static org.apache.solr.common.cloud.ZkStateReader.SHARD_ID_PROP;
import static org.apache.solr.common.params.CollectionParams.CollectionAction.ADDREPLICA;
import static org.apache.solr.common.params.CollectionParams.CollectionAction.CREATESHARD;
import static org.apache.solr.common.params.CollectionParams.CollectionAction.DELETESHARD;
import static org.apache.solr.common.params.CommonAdminParams.ASYNC;
import static org.apache.solr.common.params.CommonAdminParams.NUM_SUB_SHARDS;


public class SplitShardCmd implements OverseerCollectionMessageHandler.Cmd {
  private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
  private static final int MIN_NUM_SUB_SHARDS = 2;
  // This is an arbitrary number that seems reasonable at this time.
  private static final int MAX_NUM_SUB_SHARDS = 8;
  private static final int DEFAULT_NUM_SUB_SHARDS = 2;

  private final OverseerCollectionMessageHandler ocmh;

  public SplitShardCmd(OverseerCollectionMessageHandler ocmh) {
    this.ocmh = ocmh;
  }

  @Override
  public void call(ClusterState state, ZkNodeProps message, NamedList results) throws Exception {
    split(state, message, results);
  }

  public boolean split(ClusterState clusterState, ZkNodeProps message, NamedList results) throws Exception {
    boolean waitForFinalState = message.getBool(CommonAdminParams.WAIT_FOR_FINAL_STATE, false);
    String methodStr = message.getStr(CommonAdminParams.SPLIT_METHOD, SolrIndexSplitter.SplitMethod.REWRITE.toLower());
    SolrIndexSplitter.SplitMethod splitMethod = SolrIndexSplitter.SplitMethod.get(methodStr);
    if (splitMethod == null) {
      throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "Unknown value '" + CommonAdminParams.SPLIT_METHOD +
          ": " + methodStr);
    }
    boolean withTiming = message.getBool(CommonParams.TIMING, false);

    String collectionName = message.getStr(CoreAdminParams.COLLECTION);

    log.debug("Split shard invoked: {}", message);
    ZkStateReader zkStateReader = ocmh.zkStateReader;
    zkStateReader.forceUpdateCollection(collectionName);
    AtomicReference<String> slice = new AtomicReference<>();
    slice.set(message.getStr(ZkStateReader.SHARD_ID_PROP));
    Set<String> offlineSlices = new HashSet<>();
    RTimerTree timings = new RTimerTree();

    String splitKey = message.getStr("split.key");
    DocCollection collection = clusterState.getCollection(collectionName);

    PolicyHelper.SessionWrapper sessionWrapper = null;

    Slice parentSlice = getParentSlice(clusterState, collectionName, slice, splitKey);
    if (parentSlice.getState() != Slice.State.ACTIVE) {
      throw new SolrException(SolrException.ErrorCode.INVALID_STATE, "Parent slice is not active: " +
          collectionName + "/ " + parentSlice.getName() + ", state=" + parentSlice.getState());
    }

    // find the leader for the shard
    Replica parentShardLeader;
    try {
      parentShardLeader = zkStateReader.getLeaderRetry(collectionName, slice.get(), 10000);
    } catch (InterruptedException e) {
      Thread.currentThread().interrupt();
      throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "Interrupted.");
    }

    RTimerTree t = timings.sub("checkDiskSpace");
    checkDiskSpace(collectionName, slice.get(), parentShardLeader);
    t.stop();

    // let's record the ephemeralOwner of the parent leader node
    Stat leaderZnodeStat = zkStateReader.getZkClient().exists(ZkStateReader.LIVE_NODES_ZKNODE + "/" + parentShardLeader.getNodeName(), null, true);
    if (leaderZnodeStat == null)  {
      // we just got to know the leader but its live node is gone already!
      throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "The shard leader node: " + parentShardLeader.getNodeName() + " is not live anymore!");
    }

    List<DocRouter.Range> subRanges = new ArrayList<>();
    List<String> subSlices = new ArrayList<>();
    List<String> subShardNames = new ArrayList<>();

    // reproduce the currently existing number of replicas per type
    AtomicInteger numNrt = new AtomicInteger();
    AtomicInteger numTlog = new AtomicInteger();
    AtomicInteger numPull = new AtomicInteger();
    parentSlice.getReplicas().forEach(r -> {
      switch (r.getType()) {
        case NRT:
          numNrt.incrementAndGet();
          break;
        case TLOG:
          numTlog.incrementAndGet();
          break;
        case PULL:
          numPull.incrementAndGet();
      }
    });
    int repFactor = numNrt.get() + numTlog.get() + numPull.get();

    boolean success = false;
    try {
      // type of the first subreplica will be the same as leader
      boolean firstNrtReplica = parentShardLeader.getType() == Replica.Type.NRT;
      // verify that we indeed have the right number of correct replica types
      if ((firstNrtReplica && numNrt.get() < 1) || (!firstNrtReplica && numTlog.get() < 1)) {
        throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "aborting split - inconsistent replica types in collection " + collectionName +
            ": nrt=" + numNrt.get() + ", tlog=" + numTlog.get() + ", pull=" + numPull.get() + ", shard leader type is " +
            parentShardLeader.getType());
      }

      // check for the lock
      if (!lockForSplit(ocmh.cloudManager, collectionName, parentSlice.getName())) {
        // mark as success to avoid clearing the lock in the "finally" block
        success = true;
        throw new SolrException(SolrException.ErrorCode.INVALID_STATE, "Can't lock parent slice for splitting (another split operation running?): " +
            collectionName + "/" + parentSlice.getName());
      }

      List<Map<String, Object>> replicas = new ArrayList<>((repFactor - 1) * 2);

      t = timings.sub("fillRanges");
      String rangesStr = fillRanges(ocmh.cloudManager, message, collection, parentSlice, subRanges, subSlices, subShardNames, firstNrtReplica);
      t.stop();

      boolean oldShardsDeleted = false;
      for (String subSlice : subSlices) {
        Slice oSlice = collection.getSlice(subSlice);
        if (oSlice != null) {
          final Slice.State state = oSlice.getState();
          if (state == Slice.State.ACTIVE) {
            throw new SolrException(SolrException.ErrorCode.BAD_REQUEST,
                "Sub-shard: " + subSlice + " exists in active state. Aborting split shard.");
          } else {
            // delete the shards
            log.info("Sub-shard: {} already exists therefore requesting its deletion", subSlice);
            Map<String, Object> propMap = new HashMap<>();
            propMap.put(Overseer.QUEUE_OPERATION, "deleteshard");
            propMap.put(COLLECTION_PROP, collectionName);
            propMap.put(SHARD_ID_PROP, subSlice);
            ZkNodeProps m = new ZkNodeProps(propMap);
            try {
              ocmh.commandMap.get(DELETESHARD).call(clusterState, m, new NamedList());
            } catch (Exception e) {
              throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "Unable to delete already existing sub shard: " + subSlice,
                  e);
            }

            oldShardsDeleted = true;
          }
        }
      }

      if (oldShardsDeleted) {
        // refresh the locally cached cluster state
        // we know we have the latest because otherwise deleteshard would have failed
        clusterState = zkStateReader.getClusterState();
        collection = clusterState.getCollection(collectionName);
      }

      final String asyncId = message.getStr(ASYNC);
      Map<String, String> requestMap = new HashMap<>();
      String nodeName = parentShardLeader.getNodeName();

      t = timings.sub("createSubSlicesAndLeadersInState");
      for (int i = 0; i < subRanges.size(); i++) {
        String subSlice = subSlices.get(i);
        String subShardName = subShardNames.get(i);
        DocRouter.Range subRange = subRanges.get(i);

        log.debug("Creating slice " + subSlice + " of collection " + collectionName + " on " + nodeName);

        Map<String, Object> propMap = new HashMap<>();
        propMap.put(Overseer.QUEUE_OPERATION, CREATESHARD.toLower());
        propMap.put(ZkStateReader.SHARD_ID_PROP, subSlice);
        propMap.put(ZkStateReader.COLLECTION_PROP, collectionName);
        propMap.put(ZkStateReader.SHARD_RANGE_PROP, subRange.toString());
        propMap.put(ZkStateReader.SHARD_STATE_PROP, Slice.State.CONSTRUCTION.toString());
        propMap.put(ZkStateReader.SHARD_PARENT_PROP, parentSlice.getName());
        propMap.put("shard_parent_node", nodeName);
        propMap.put("shard_parent_zk_session", leaderZnodeStat.getEphemeralOwner());
        DistributedQueue inQueue = Overseer.getStateUpdateQueue(zkStateReader.getZkClient());
        inQueue.offer(Utils.toJSON(new ZkNodeProps(propMap)));

        // wait until we are able to see the new shard in cluster state
        ocmh.waitForNewShard(collectionName, subSlice);

        // refresh cluster state
        clusterState = zkStateReader.getClusterState();

        log.debug("Adding first replica " + subShardName + " as part of slice " + subSlice + " of collection " + collectionName
            + " on " + nodeName);
        propMap = new HashMap<>();
        propMap.put(Overseer.QUEUE_OPERATION, ADDREPLICA.toLower());
        propMap.put(COLLECTION_PROP, collectionName);
        propMap.put(SHARD_ID_PROP, subSlice);
        propMap.put(REPLICA_TYPE, firstNrtReplica ? Replica.Type.NRT.toString() : Replica.Type.TLOG.toString());
        propMap.put("node", nodeName);
        propMap.put(CoreAdminParams.NAME, subShardName);
        propMap.put(CommonAdminParams.WAIT_FOR_FINAL_STATE, Boolean.toString(waitForFinalState));
        // copy over property params:
        for (String key : message.keySet()) {
          if (key.startsWith(OverseerCollectionMessageHandler.COLL_PROP_PREFIX)) {
            propMap.put(key, message.getStr(key));
          }
        }
        // add async param
        if (asyncId != null) {
          propMap.put(ASYNC, asyncId);
        }
        ocmh.addReplica(clusterState, new ZkNodeProps(propMap), results, null);
      }

      ShardHandler shardHandler = ocmh.shardHandlerFactory.getShardHandler();

      ocmh.processResponses(results, shardHandler, true, "SPLITSHARD failed to create subshard leaders", asyncId, requestMap);

      t.stop();
      t = timings.sub("waitForSubSliceLeadersAlive");
      for (String subShardName : subShardNames) {
        // wait for parent leader to acknowledge the sub-shard core
        log.debug("Asking parent leader to wait for: " + subShardName + " to be alive on: " + nodeName);
        String coreNodeName = ocmh.waitForCoreNodeName(collectionName, nodeName, subShardName);
        CoreAdminRequest.WaitForState cmd = new CoreAdminRequest.WaitForState();
        cmd.setCoreName(subShardName);
        cmd.setNodeName(nodeName);
        cmd.setCoreNodeName(coreNodeName);
        cmd.setState(Replica.State.ACTIVE);
        cmd.setCheckLive(true);
        cmd.setOnlyIfLeader(true);

        ModifiableSolrParams p = new ModifiableSolrParams(cmd.getParams());
        ocmh.sendShardRequest(nodeName, p, shardHandler, asyncId, requestMap);
      }

      ocmh.processResponses(results, shardHandler, true, "SPLITSHARD timed out waiting for subshard leaders to come up",
          asyncId, requestMap);
      t.stop();

      log.debug("Successfully created all sub-shards for collection " + collectionName + " parent shard: " + slice
          + " on: " + parentShardLeader);

      log.info("Splitting shard " + parentShardLeader.getName() + " as part of slice " + slice + " of collection "
          + collectionName + " on " + parentShardLeader);

      ModifiableSolrParams params = new ModifiableSolrParams();
      params.set(CoreAdminParams.ACTION, CoreAdminParams.CoreAdminAction.SPLIT.toString());
      params.set(CommonAdminParams.SPLIT_METHOD, splitMethod.toLower());
      params.set(CoreAdminParams.CORE, parentShardLeader.getStr("core"));
      for (int i = 0; i < subShardNames.size(); i++) {
        String subShardName = subShardNames.get(i);
        params.add(CoreAdminParams.TARGET_CORE, subShardName);
      }
      params.set(CoreAdminParams.RANGES, rangesStr);

      t = timings.sub("splitParentCore");

      ocmh.sendShardRequest(parentShardLeader.getNodeName(), params, shardHandler, asyncId, requestMap);

      ocmh.processResponses(results, shardHandler, true, "SPLITSHARD failed to invoke SPLIT core admin command", asyncId,
          requestMap);
      t.stop();

      log.debug("Index on shard: {} split into {} successfully", nodeName, subShardNames.size());

      t = timings.sub("applyBufferedUpdates");
      // apply buffered updates on sub-shards
      for (int i = 0; i < subShardNames.size(); i++) {
        String subShardName = subShardNames.get(i);

        log.debug("Applying buffered updates on : " + subShardName);

        params = new ModifiableSolrParams();
        params.set(CoreAdminParams.ACTION, CoreAdminParams.CoreAdminAction.REQUESTAPPLYUPDATES.toString());
        params.set(CoreAdminParams.NAME, subShardName);

        ocmh.sendShardRequest(nodeName, params, shardHandler, asyncId, requestMap);
      }

      ocmh.processResponses(results, shardHandler, true, "SPLITSHARD failed while asking sub shard leaders" +
          " to apply buffered updates", asyncId, requestMap);
      t.stop();

      log.debug("Successfully applied buffered updates on : " + subShardNames);

      // Replica creation for the new Slices
      // replica placement is controlled by the autoscaling policy framework

      Set<String> nodes = clusterState.getLiveNodes();
      List<String> nodeList = new ArrayList<>(nodes.size());
      nodeList.addAll(nodes);

      // TODO: Have maxShardsPerNode param for this operation?

      // Remove the node that hosts the parent shard for replica creation.
      nodeList.remove(nodeName);

      // TODO: change this to handle sharding a slice into > 2 sub-shards.

      // we have already created one subReplica for each subShard on the parent node.
      // identify locations for the remaining replicas
      if (firstNrtReplica) {
        numNrt.decrementAndGet();
      } else {
        numTlog.decrementAndGet();
      }

      t = timings.sub("identifyNodesForReplicas");
      Assign.AssignRequest assignRequest = new Assign.AssignRequestBuilder()
          .forCollection(collectionName)
          .forShard(subSlices)
          .assignNrtReplicas(numNrt.get())
          .assignTlogReplicas(numTlog.get())
          .assignPullReplicas(numPull.get())
          .onNodes(new ArrayList<>(clusterState.getLiveNodes()))
          .build();
      Assign.AssignStrategyFactory assignStrategyFactory = new Assign.AssignStrategyFactory(ocmh.cloudManager);
      Assign.AssignStrategy assignStrategy = assignStrategyFactory.create(clusterState, collection);
      List<ReplicaPosition> replicaPositions = assignStrategy.assign(ocmh.cloudManager, assignRequest);
      sessionWrapper = PolicyHelper.getLastSessionWrapper(true);
      t.stop();

      t = timings.sub("createReplicaPlaceholders");
      for (ReplicaPosition replicaPosition : replicaPositions) {
        String sliceName = replicaPosition.shard;
        String subShardNodeName = replicaPosition.node;
        String solrCoreName = Assign.buildSolrCoreName(collectionName, sliceName, replicaPosition.type, replicaPosition.index);

        log.debug("Creating replica shard " + solrCoreName + " as part of slice " + sliceName + " of collection "
            + collectionName + " on " + subShardNodeName);

        // we first create all replicas in DOWN state without actually creating their cores in order to
        // avoid a race condition where Overseer may prematurely activate the new sub-slices (and deactivate
        // the parent slice) before all new replicas are added. This situation may lead to a loss of performance
        // because the new shards will be activated with possibly many fewer replicas.
        ZkNodeProps props = new ZkNodeProps(Overseer.QUEUE_OPERATION, ADDREPLICA.toLower(),
            ZkStateReader.COLLECTION_PROP, collectionName,
            ZkStateReader.SHARD_ID_PROP, sliceName,
            ZkStateReader.CORE_NAME_PROP, solrCoreName,
            ZkStateReader.REPLICA_TYPE, replicaPosition.type.name(),
            ZkStateReader.STATE_PROP, Replica.State.DOWN.toString(),
            ZkStateReader.BASE_URL_PROP, zkStateReader.getBaseUrlForNodeName(subShardNodeName),
            ZkStateReader.NODE_NAME_PROP, subShardNodeName,
            CommonAdminParams.WAIT_FOR_FINAL_STATE, Boolean.toString(waitForFinalState));
        Overseer.getStateUpdateQueue(zkStateReader.getZkClient()).offer(Utils.toJSON(props));

        HashMap<String, Object> propMap = new HashMap<>();
        propMap.put(Overseer.QUEUE_OPERATION, ADDREPLICA.toLower());
        propMap.put(COLLECTION_PROP, collectionName);
        propMap.put(SHARD_ID_PROP, sliceName);
        propMap.put(REPLICA_TYPE, replicaPosition.type.name());
        propMap.put("node", subShardNodeName);
        propMap.put(CoreAdminParams.NAME, solrCoreName);
        // copy over property params:
        for (String key : message.keySet()) {
          if (key.startsWith(OverseerCollectionMessageHandler.COLL_PROP_PREFIX)) {
            propMap.put(key, message.getStr(key));
          }
        }
        // add async param
        if (asyncId != null) {
          propMap.put(ASYNC, asyncId);
        }
        // special flag param to instruct addReplica not to create the replica in cluster state again
        propMap.put(OverseerCollectionMessageHandler.SKIP_CREATE_REPLICA_IN_CLUSTER_STATE, "true");

        propMap.put(CommonAdminParams.WAIT_FOR_FINAL_STATE, Boolean.toString(waitForFinalState));

        replicas.add(propMap);
      }
      t.stop();
      assert TestInjection.injectSplitFailureBeforeReplicaCreation();

      long ephemeralOwner = leaderZnodeStat.getEphemeralOwner();
      // compare against the ephemeralOwner of the parent leader node
      leaderZnodeStat = zkStateReader.getZkClient().exists(ZkStateReader.LIVE_NODES_ZKNODE + "/" + parentShardLeader.getNodeName(), null, true);
      if (leaderZnodeStat == null || ephemeralOwner != leaderZnodeStat.getEphemeralOwner()) {
        // put sub-shards in recovery_failed state
        DistributedQueue inQueue = Overseer.getStateUpdateQueue(zkStateReader.getZkClient());
        Map<String, Object> propMap = new HashMap<>();
        propMap.put(Overseer.QUEUE_OPERATION, OverseerAction.UPDATESHARDSTATE.toLower());
        for (String subSlice : subSlices) {
          propMap.put(subSlice, Slice.State.RECOVERY_FAILED.toString());
        }
        propMap.put(ZkStateReader.COLLECTION_PROP, collectionName);
        ZkNodeProps m = new ZkNodeProps(propMap);
        inQueue.offer(Utils.toJSON(m));

        if (leaderZnodeStat == null)  {
          // the leader is not live anymore, fail the split!
          throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "The shard leader node: " + parentShardLeader.getNodeName() + " is not live anymore!");
        } else if (ephemeralOwner != leaderZnodeStat.getEphemeralOwner()) {
          // there's a new leader, fail the split!
          throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,
              "The zk session id for the shard leader node: " + parentShardLeader.getNodeName() + " has changed from "
                  + ephemeralOwner + " to " + leaderZnodeStat.getEphemeralOwner() + ". This can cause data loss so we must abort the split");
        }
      }

      // we must set the slice state into recovery before actually creating the replica cores
      // this ensures that the logic inside ReplicaMutator to update sub-shard state to 'active'
      // always gets a chance to execute. See SOLR-7673

      if (repFactor == 1) {
        // switch sub shard states to 'active'
        log.debug("Replication factor is 1 so switching shard states");
        DistributedQueue inQueue = Overseer.getStateUpdateQueue(zkStateReader.getZkClient());
        Map<String, Object> propMap = new HashMap<>();
        propMap.put(Overseer.QUEUE_OPERATION, OverseerAction.UPDATESHARDSTATE.toLower());
        propMap.put(slice.get(), Slice.State.INACTIVE.toString());
        for (String subSlice : subSlices) {
          propMap.put(subSlice, Slice.State.ACTIVE.toString());
        }
        propMap.put(ZkStateReader.COLLECTION_PROP, collectionName);
        ZkNodeProps m = new ZkNodeProps(propMap);
        inQueue.offer(Utils.toJSON(m));
      } else {
        log.debug("Requesting shard state be set to 'recovery'");
        DistributedQueue inQueue = Overseer.getStateUpdateQueue(zkStateReader.getZkClient());
        Map<String, Object> propMap = new HashMap<>();
        propMap.put(Overseer.QUEUE_OPERATION, OverseerAction.UPDATESHARDSTATE.toLower());
        for (String subSlice : subSlices) {
          propMap.put(subSlice, Slice.State.RECOVERY.toString());
        }
        propMap.put(ZkStateReader.COLLECTION_PROP, collectionName);
        ZkNodeProps m = new ZkNodeProps(propMap);
        inQueue.offer(Utils.toJSON(m));
      }

      t = timings.sub("createCoresForReplicas");
      // now actually create replica cores on sub shard nodes
      for (Map<String, Object> replica : replicas) {
        ocmh.addReplica(clusterState, new ZkNodeProps(replica), results, null);
      }

      assert TestInjection.injectSplitFailureAfterReplicaCreation();

      ocmh.processResponses(results, shardHandler, true, "SPLITSHARD failed to create subshard replicas", asyncId, requestMap);
      t.stop();

      log.info("Successfully created all replica shards for all sub-slices " + subSlices);

      t = timings.sub("finalCommit");
      ocmh.commit(results, slice.get(), parentShardLeader);
      t.stop();
      if (withTiming) {
        results.add(CommonParams.TIMING, timings.asNamedList());
      }
      success = true;
      // don't unlock the shard yet - only do this if the final switch-over in
      // ReplicaMutator succeeds (or fails)
      return true;
    } catch (SolrException e) {
      throw e;
    } catch (Exception e) {
      log.error("Error executing split operation for collection: " + collectionName + " parent shard: " + slice, e);
      throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, null, e);
    } finally {
      if (sessionWrapper != null) sessionWrapper.release();
      if (!success) {
        cleanupAfterFailure(zkStateReader, collectionName, parentSlice.getName(), subSlices, offlineSlices);
        unlockForSplit(ocmh.cloudManager, collectionName, parentSlice.getName());
      }
    }
  }

  private void checkDiskSpace(String collection, String shard, Replica parentShardLeader) throws SolrException {
    // check that enough disk space is available on the parent leader node
    // otherwise the actual index splitting will always fail
    NodeStateProvider nodeStateProvider = ocmh.cloudManager.getNodeStateProvider();
    Map<String, Object> nodeValues = nodeStateProvider.getNodeValues(parentShardLeader.getNodeName(),
        Collections.singletonList(ImplicitSnitch.DISK));
    Map<String, Map<String, List<ReplicaInfo>>> infos = nodeStateProvider.getReplicaInfo(parentShardLeader.getNodeName(),
        Collections.singletonList(Type.CORE_IDX.metricsAttribute));
    if (infos.get(collection) == null || infos.get(collection).get(shard) == null) {
      throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "missing replica information for parent shard leader");
    }
    // find the leader
    List<ReplicaInfo> lst = infos.get(collection).get(shard);
    Double indexSize = null;
    for (ReplicaInfo info : lst) {
      if (info.getCore().equals(parentShardLeader.getCoreName())) {
        Number size = (Number)info.getVariable(Type.CORE_IDX.metricsAttribute);
        if (size == null) {
          throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "missing index size information for parent shard leader");
        }
        indexSize = (Double) Type.CORE_IDX.convertVal(size);
        break;
      }
    }
    if (indexSize == null) {
      throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "missing replica information for parent shard leader");
    }
    Number freeSize = (Number)nodeValues.get(ImplicitSnitch.DISK);
    if (freeSize == null) {
      throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "missing node disk space information for parent shard leader");
    }
    if (freeSize.doubleValue() < 2.0 * indexSize) {
      throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "not enough free disk space to perform index split on node " +
          parentShardLeader.getNodeName() + ", required: " + (2 * indexSize) + ", available: " + freeSize);
    }
  }

  private void cleanupAfterFailure(ZkStateReader zkStateReader, String collectionName, String parentShard,
                                   List<String> subSlices, Set<String> offlineSlices) {
    log.info("Cleaning up after a failed split of " + collectionName + "/" + parentShard);
    // get the latest state
    try {
      zkStateReader.forceUpdateCollection(collectionName);
    } catch (KeeperException | InterruptedException e) {
      log.warn("Cleanup failed after failed split of " + collectionName + "/" + parentShard + ": (force update collection)", e);
      return;
    }
    ClusterState clusterState = zkStateReader.getClusterState();
    DocCollection coll = clusterState.getCollectionOrNull(collectionName);

    if (coll == null) { // may have been deleted
      return;
    }

    // set already created sub shards states to CONSTRUCTION - this prevents them
    // from entering into RECOVERY or ACTIVE (SOLR-9455)
    DistributedQueue inQueue = Overseer.getStateUpdateQueue(zkStateReader.getZkClient());
    final Map<String, Object> propMap = new HashMap<>();
    boolean sendUpdateState = false;
    propMap.put(Overseer.QUEUE_OPERATION, OverseerAction.UPDATESHARDSTATE.toLower());
    propMap.put(ZkStateReader.COLLECTION_PROP, collectionName);
    for (Slice s : coll.getSlices()) {
      if (!subSlices.contains(s.getName())) {
        continue;
      }
      propMap.put(s.getName(), Slice.State.CONSTRUCTION.toString());
      sendUpdateState = true;
    }

    // if parent is inactive activate it again
    Slice parentSlice = coll.getSlice(parentShard);
    if (parentSlice.getState() == Slice.State.INACTIVE) {
      sendUpdateState = true;
      propMap.put(parentShard, Slice.State.ACTIVE.toString());
    }
    // plus any other previously deactivated slices
    for (String sliceName : offlineSlices) {
      propMap.put(sliceName, Slice.State.ACTIVE.toString());
      sendUpdateState = true;
    }

    if (sendUpdateState) {
      try {
        ZkNodeProps m = new ZkNodeProps(propMap);
        inQueue.offer(Utils.toJSON(m));
      } catch (Exception e) {
        // don't give up yet - just log the error, we may still be able to clean up
        log.warn("Cleanup failed after failed split of " + collectionName + "/" + parentShard + ": (slice state changes)", e);
      }
    }

    // delete existing subShards
    for (String subSlice : subSlices) {
      Slice s = coll.getSlice(subSlice);
      if (s == null) {
        continue;
      }
      log.debug("- sub-shard: {} exists therefore requesting its deletion", subSlice);
      HashMap<String, Object> props = new HashMap<>();
      props.put(Overseer.QUEUE_OPERATION, "deleteshard");
      props.put(COLLECTION_PROP, collectionName);
      props.put(SHARD_ID_PROP, subSlice);
      ZkNodeProps m = new ZkNodeProps(props);
      try {
        ocmh.commandMap.get(DELETESHARD).call(clusterState, m, new NamedList());
      } catch (Exception e) {
        log.warn("Cleanup failed after failed split of " + collectionName + "/" + parentShard + ": (deleting existing sub shard " + subSlice + ")", e);
      }
    }
  }

  public static Slice getParentSlice(ClusterState clusterState, String collectionName, AtomicReference<String> slice, String splitKey) {
    DocCollection collection = clusterState.getCollection(collectionName);
    DocRouter router = collection.getRouter() != null ? collection.getRouter() : DocRouter.DEFAULT;

    Slice parentSlice;

    if (slice.get() == null) {
      if (router instanceof CompositeIdRouter) {
        Collection<Slice> searchSlices = router.getSearchSlicesSingle(splitKey, new ModifiableSolrParams(), collection);
        if (searchSlices.isEmpty()) {
          throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "Unable to find an active shard for split.key: " + splitKey);
        }
        if (searchSlices.size() > 1) {
          throw new SolrException(SolrException.ErrorCode.BAD_REQUEST,
              "Splitting a split.key: " + splitKey + " which spans multiple shards is not supported");
        }
        parentSlice = searchSlices.iterator().next();
        slice.set(parentSlice.getName());
        log.info("Split by route.key: {}, parent shard is: {} ", splitKey, slice);
      } else {
        throw new SolrException(SolrException.ErrorCode.BAD_REQUEST,
            "Split by route key can only be used with CompositeIdRouter or subclass. Found router: "
                + router.getClass().getName());
      }
    } else {
      parentSlice = collection.getSlice(slice.get());
    }

    if (parentSlice == null) {
      // no chance of the collection being null because ClusterState#getCollection(String) would have thrown
      // an exception already
      throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "No shard with the specified name exists: " + slice);
    }
    return parentSlice;
  }

  public static String fillRanges(SolrCloudManager cloudManager, ZkNodeProps message, DocCollection collection, Slice parentSlice,
                                List<DocRouter.Range> subRanges, List<String> subSlices, List<String> subShardNames,
                                  boolean firstReplicaNrt) {
    String splitKey = message.getStr("split.key");
    String rangesStr = message.getStr(CoreAdminParams.RANGES);
    String fuzzStr = message.getStr(CommonAdminParams.SPLIT_FUZZ, "0");
    float fuzz = 0.0f;
    try {
      fuzz = Float.parseFloat(fuzzStr);
    } catch (Exception e) {
      throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "?Invalid numeric value of 'fuzz': " + fuzzStr);
    }

    DocRouter.Range range = parentSlice.getRange();
    if (range == null) {
      range = new PlainIdRouter().fullRange();
    }
    DocRouter router = collection.getRouter() != null ? collection.getRouter() : DocRouter.DEFAULT;
    if (rangesStr != null) {
      String[] ranges = rangesStr.split(",");
      if (ranges.length == 0 || ranges.length == 1) {
        throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "There must be at least two ranges specified to split a shard");
      } else {
        for (int i = 0; i < ranges.length; i++) {
          String r = ranges[i];
          try {
            subRanges.add(DocRouter.DEFAULT.fromString(r));
          } catch (Exception e) {
            throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "Exception in parsing hexadecimal hash range: " + r, e);
          }
          if (!subRanges.get(i).isSubsetOf(range)) {
            throw new SolrException(SolrException.ErrorCode.BAD_REQUEST,
                "Specified hash range: " + r + " is not a subset of parent shard's range: " + range.toString());
          }
        }
        List<DocRouter.Range> temp = new ArrayList<>(subRanges); // copy to preserve original order
        Collections.sort(temp);
        if (!range.equals(new DocRouter.Range(temp.get(0).min, temp.get(temp.size() - 1).max))) {
          throw new SolrException(SolrException.ErrorCode.BAD_REQUEST,
              "Specified hash ranges: " + rangesStr + " do not cover the entire range of parent shard: " + range);
        }
        for (int i = 1; i < temp.size(); i++) {
          if (temp.get(i - 1).max + 1 != temp.get(i).min) {
            throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "Specified hash ranges: " + rangesStr
                + " either overlap with each other or " + "do not cover the entire range of parent shard: " + range);
          }
        }
      }
    } else if (splitKey != null) {
      if (router instanceof CompositeIdRouter) {
        CompositeIdRouter compositeIdRouter = (CompositeIdRouter) router;
        List<DocRouter.Range> tmpSubRanges = compositeIdRouter.partitionRangeByKey(splitKey, range);
        if (tmpSubRanges.size() == 1) {
          throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "The split.key: " + splitKey
              + " has a hash range that is exactly equal to hash range of shard: " + parentSlice.getName());
        }
        for (DocRouter.Range subRange : tmpSubRanges) {
          if (subRange.min == subRange.max) {
            throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "The split.key: " + splitKey + " must be a compositeId");
          }
        }
        subRanges.addAll(tmpSubRanges);
        log.info("Partitioning parent shard " + parentSlice.getName() + " range: " + parentSlice.getRange() + " yields: " + subRanges);
        rangesStr = "";
        for (int i = 0; i < subRanges.size(); i++) {
          DocRouter.Range subRange = subRanges.get(i);
          rangesStr += subRange.toString();
          if (i < subRanges.size() - 1) rangesStr += ',';
        }
      }
    } else {
      int numSubShards = message.getInt(NUM_SUB_SHARDS, DEFAULT_NUM_SUB_SHARDS);
      log.info("{} set at: {}", NUM_SUB_SHARDS, numSubShards);

      if(numSubShards < MIN_NUM_SUB_SHARDS || numSubShards > MAX_NUM_SUB_SHARDS)
        throw new SolrException(SolrException.ErrorCode.BAD_REQUEST,
            "A shard can only be split into "+MIN_NUM_SUB_SHARDS+" to " + MAX_NUM_SUB_SHARDS
            + " subshards in one split request. Provided "+NUM_SUB_SHARDS+"=" + numSubShards);
      subRanges.addAll(router.partitionRange(numSubShards, range, fuzz));
    }

    for (int i = 0; i < subRanges.size(); i++) {
      String subSlice = parentSlice.getName() + "_" + i;
      subSlices.add(subSlice);
      String subShardName = Assign.buildSolrCoreName(cloudManager.getDistribStateManager(), collection, subSlice,
          firstReplicaNrt ? Replica.Type.NRT : Replica.Type.TLOG);
      subShardNames.add(subShardName);
    }
    return rangesStr;
  }

  public static boolean lockForSplit(SolrCloudManager cloudManager, String collection, String shard) throws Exception {
    String path = ZkStateReader.COLLECTIONS_ZKNODE + "/" + collection + "/" + shard + "-splitting";
    log.info("===locking " + path, new Exception());
    final DistribStateManager stateManager = cloudManager.getDistribStateManager();
    synchronized (stateManager) {
      if (stateManager.hasData(path)) {
        VersionedData vd = stateManager.getData(path);
        log.info("=== already locked! {}", Utils.fromJSON(vd.getData()));
        return false;
      }
      Map<String, Object> map = new HashMap<>();
      map.put(ZkStateReader.STATE_TIMESTAMP_PROP, String.valueOf(cloudManager.getTimeSource().getEpochTimeNs()));
      byte[] data = Utils.toJSON(map);
      try {
        cloudManager.getDistribStateManager().makePath(path, data, CreateMode.EPHEMERAL, true);
      } catch (Exception e) {
        throw new SolrException(SolrException.ErrorCode.INVALID_STATE, "Can't lock parent slice for splitting (another split operation running?): " +
            collection + "/" + shard, e);
      }
      return true;
    }
  }

  public static void unlockForSplit(SolrCloudManager cloudManager, String collection, String shard) throws Exception {
    if (shard != null) {
      String path = ZkStateReader.COLLECTIONS_ZKNODE + "/" + collection + "/" + shard + "-splitting";
      cloudManager.getDistribStateManager().removeRecursively(path, true, true);
    } else {
      String path = ZkStateReader.COLLECTIONS_ZKNODE + "/" + collection;
      try {
        List<String> names = cloudManager.getDistribStateManager().listData(path);
        for (String name : cloudManager.getDistribStateManager().listData(path)) {
          if (name.endsWith("-splitting")) {
            try {
              cloudManager.getDistribStateManager().removeData(path + "/" + name, -1);
            } catch (NoSuchElementException nse) {
              // ignore
            }
          }
        }
      } catch (NoSuchElementException nse) {
        // ignore
      }
    }
  }
}