/*
 *
 *  *  Copyright 2010-2016 OrientDB LTD (http://orientdb.com)
 *  *
 *  *  Licensed 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.
 *  *
 *  * For more information: http://orientdb.com
 *
 */
package com.orientechnologies.orient.server.distributed;

import com.orientechnologies.common.log.OLogManager;
import com.orientechnologies.orient.core.exception.OConfigurationException;
import com.orientechnologies.orient.core.record.impl.ODocument;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;

/**
 * Immutable Distributed configuration. It uses an ODocument object to store the configuration.
 * Every changes must be done by obtaining a modifiable verson of the object through the method
 * `modify()`.
 *
 * @author Luca Garulli (l.garulli--(at)--orientdb.com)
 */
public class ODistributedConfiguration {
  public static final String NEW_NODE_TAG = "<NEW_NODE>";
  public static final String ALL_WILDCARD = "*";

  protected static final String SERVERS = "servers";
  protected static final String DCS = "dataCenters";
  protected static final String OWNER = "owner";
  protected static final String CLUSTERS = "clusters";
  protected static final String VERSION = "version";

  protected static final String AUTO_DEPLOY = "autoDeploy";
  protected static final String READ_QUORUM = "readQuorum";
  protected static final String WRITE_QUORUM = "writeQuorum";
  public static final String QUORUM_MAJORITY = "majority";
  public static final String QUORUM_ALL = "all";
  public static final String QUORUM_LOCAL_DC = "localDataCenter";
  public static final Integer DEFAULT_READ_QUORUM = 1;
  public static final String DEFAULT_WRITE_QUORUM = QUORUM_MAJORITY;

  protected static final String NEW_NODE_STRATEGY = "newNodeStrategy";
  protected static final String READ_YOUR_WRITES = "readYourWrites";
  protected static final String EXECUTION_MODE = "executionMode";
  protected static final String EXECUTION_MODE_SYNCHRONOUS = "synchronous";

  protected final ODocument configuration;
  protected static final List<String> DEFAULT_CLUSTER_NAME =
      Collections.singletonList(ALL_WILDCARD);
  private static ThreadLocal<Integer> overwriteWriteQuorum = new ThreadLocal<Integer>();

  public enum ROLES {
    MASTER,
    REPLICA
  }

  public enum NEW_NODE_STRATEGIES {
    DYNAMIC,
    STATIC
  }

  public ODistributedConfiguration(final ODocument iConfiguration) {
    configuration = iConfiguration;
    configuration.setTrackingChanges(false);
  }

  public OModifiableDistributedConfiguration modify() {
    return new OModifiableDistributedConfiguration(configuration.copy());
  }

  /**
   * Returns true if the replication is active, otherwise false.
   *
   * @param iClusterName Cluster name, or null for *
   */
  public boolean isReplicationActive(final String iClusterName, final String iLocalNode) {
    final Collection<String> servers = getClusterConfiguration(iClusterName).field(SERVERS);
    if (servers != null && !servers.isEmpty()) {
      return true;
    }
    return false;
  }

  /** Returns true if the configuration per data centers is specified. */
  public boolean hasDataCenterConfiguration() {
    return configuration.field(DCS) != null;
  }

  public boolean isAutoDeploy() {
    return configuration.field(AUTO_DEPLOY) != null
        ? (Boolean) configuration.field(AUTO_DEPLOY)
        : true;
  }

  /**
   * Returns the new node strategy between "dynamic" and "static". If static, the node is registered
   * under the "server" tag.
   *
   * @return NEW_NODE_STRATEGIES enum
   */
  public NEW_NODE_STRATEGIES getNewNodeStrategy() {

    final String value = configuration.field(NEW_NODE_STRATEGY);
    if (value != null) return NEW_NODE_STRATEGIES.valueOf(value.toUpperCase(Locale.ENGLISH));

    return NEW_NODE_STRATEGIES.STATIC;
  }

  /**
   * Returns the execution mode if synchronous.
   *
   * @param iClusterName Cluster name, or null for *
   * @return true = synchronous, false = asynchronous, null = undefined
   */
  public Boolean isExecutionModeSynchronous(final String iClusterName) {
    Object value = getClusterConfiguration(iClusterName).field(EXECUTION_MODE);
    if (value == null) {
      value = configuration.field(EXECUTION_MODE);
      if (value == null) return null;
    }

    if (value.toString().equalsIgnoreCase("undefined")) return null;

    return value.toString().equalsIgnoreCase(EXECUTION_MODE_SYNCHRONOUS);
  }

  /**
   * Reads your writes.
   *
   * @param iClusterName Cluster name, or null for *
   */
  public Boolean isReadYourWrites(final String iClusterName) {
    Object value = getClusterConfiguration(iClusterName).field(READ_YOUR_WRITES);
    if (value == null) {
      value = configuration.field(READ_YOUR_WRITES);
      if (value == null) {
        OLogManager.instance()
            .warn(
                this,
                "%s setting not found for cluster=%s in distributed-config.json",
                READ_YOUR_WRITES,
                iClusterName);
        return true;
      }
    }
    return (Boolean) value;
  }

  /**
   * Returns the list of servers that can manage a list of clusters. The algorithm makes its best to
   * involve the less servers as it can.
   *
   * @param iClusterNames Set of cluster names to find
   * @param iLocalNode Local node name
   */
  public Map<String, Collection<String>> getServerClusterMap(
      Collection<String> iClusterNames,
      final String iLocalNode,
      final boolean optimizeForLocalOnly) {
    if (iClusterNames == null || iClusterNames.isEmpty()) iClusterNames = DEFAULT_CLUSTER_NAME;

    final Map<String, Collection<String>> servers =
        new HashMap<String, Collection<String>>(iClusterNames.size());

    // TRY TO SEE IF IT CAN BE EXECUTED ON LOCAL NODE ONLY
    boolean canUseLocalNode = true;
    for (String p : iClusterNames) {
      final List<String> serverList = getClusterConfiguration(p).field(SERVERS);
      if (serverList != null && !serverList.contains(iLocalNode)) {
        canUseLocalNode = false;
        break;
      }
    }

    if (optimizeForLocalOnly && canUseLocalNode) {
      // USE LOCAL NODE ONLY (MUCH FASTER)
      servers.put(iLocalNode, iClusterNames);
      return servers;
    }

    // GROUP BY SERVER WITH THE NUMBER OF CLUSTERS
    final Map<String, Collection<String>> serverMap = new HashMap<String, Collection<String>>();
    for (String p : iClusterNames) {
      final List<String> serverList = getClusterConfiguration(p).field(SERVERS);
      for (String s : serverList) {
        if (NEW_NODE_TAG.equalsIgnoreCase(s)) continue;

        Collection<String> clustersInServer = serverMap.get(s);
        if (clustersInServer == null) {
          clustersInServer = new HashSet<String>();
          serverMap.put(s, clustersInServer);
        }
        clustersInServer.add(p);
      }
    }

    if (serverMap.size() == 1)
      // RETURN THE ONLY SERVER INVOLVED
      return serverMap;

    if (!optimizeForLocalOnly) return serverMap;

    // ORDER BY NUMBER OF CLUSTERS
    final List<String> orderedServers = new ArrayList<String>(serverMap.keySet());
    Collections.sort(
        orderedServers,
        new Comparator<String>() {
          @Override
          public int compare(final String o1, final String o2) {
            return ((Integer) serverMap.get(o2).size())
                .compareTo((Integer) serverMap.get(o1).size());
          }
        });

    // BROWSER ORDERED SERVER MAP PUTTING THE MINIMUM SERVER TO COVER ALL THE CLUSTERS
    final Set<String> remainingClusters =
        new HashSet<String>(iClusterNames); // KEEPS THE REMAINING CLUSTER TO ADD IN FINAL
    // RESULT
    final Set<String> includedClusters =
        new HashSet<String>(iClusterNames.size()); // KEEPS THE COLLECTION OF ALREADY INCLUDED
    // CLUSTERS
    for (String s : orderedServers) {
      final Collection<String> clusters = serverMap.get(s);

      if (!servers.isEmpty()) {
        // FILTER CLUSTER LIST AVOIDING TO REPEAT CLUSTERS ALREADY INCLUDED ON PREVIOUS NODES
        clusters.removeAll(includedClusters);
      }

      servers.put(s, clusters);
      remainingClusters.removeAll(clusters);
      includedClusters.addAll(clusters);

      if (remainingClusters.isEmpty())
        // FOUND ALL CLUSTERS
        break;
    }

    return servers;
  }

  /**
   * Returns the clusters where a server is owner. This is used when a cluster must be selected:
   * locality is always the best choice.
   *
   * @param iClusterNames Set of cluster names
   * @param iNode Node
   */
  public List<String> getOwnedClustersByServer(
      Collection<String> iClusterNames, final String iNode) {
    if (iClusterNames == null || iClusterNames.isEmpty()) iClusterNames = DEFAULT_CLUSTER_NAME;

    final List<String> notDefinedClusters = new ArrayList<String>(5);
    final List<String> candidates = new ArrayList<String>(5);

    for (String p : iClusterNames) {
      if (p == null) continue;

      final String ownerServer = getClusterOwner(p);
      if (ownerServer == null) notDefinedClusters.add(p);
      else if (iNode.equals(ownerServer)) {
        // COLLECT AS CANDIDATE
        candidates.add(p);
      }
    }

    if (!candidates.isEmpty())
      // RETURN THE FIRST ONE
      return candidates;

    final String owner = getClusterOwner(ALL_WILDCARD);
    if (iNode.equals(owner))
      // CURRENT SERVER IS MASTER OF DEFAULT: RETURN ALL THE NON CONFIGURED CLUSTERS
      return notDefinedClusters;

    // NO MASTER FOUND, RETURN EMPTY LIST
    return candidates;
  }

  /**
   * Returns the set of server names involved on the passed cluster collection.
   *
   * @param iClusterNames Collection of cluster names to find
   */
  public Set<String> getServers(Collection<String> iClusterNames) {
    if (iClusterNames == null || iClusterNames.isEmpty()) return getAllConfiguredServers();

    final Set<String> partitions = new HashSet<String>(iClusterNames.size());
    for (String p : iClusterNames) {
      final List<String> serverList = getClusterConfiguration(p).field(SERVERS);
      if (serverList != null) {
        for (String s : serverList) if (!s.equals(NEW_NODE_TAG)) partitions.add(s);
      }
    }
    return partitions;
  }

  /**
   * Returns true if the local server has all the requested clusters.
   *
   * @param server Server name
   * @param clusters Collection of cluster names to find
   */
  public boolean isServerContainingAllClusters(final String server, Collection<String> clusters) {

    if (clusters == null || clusters.isEmpty()) clusters = DEFAULT_CLUSTER_NAME;

    for (String cluster : clusters) {
      final List<String> serverList = getClusterConfiguration(cluster).field(SERVERS);
      if (serverList != null) {
        if (!serverList.contains(server)) return false;
      }
    }
    return true;
  }

  /**
   * Returns true if the local server has the requested cluster.
   *
   * @param server Server name
   * @param cluster cluster names to find
   */
  public boolean isServerContainingCluster(final String server, String cluster) {
    if (cluster == null) cluster = ALL_WILDCARD;

    final List<String> serverList = getClusterConfiguration(cluster).field(SERVERS);
    if (serverList != null) {
      return serverList.contains(server);
    }
    return true;
  }

  /**
   * Returns the server list for the requested cluster cluster excluding any tags like <NEW_NODES>
   * and iExclude if any.
   *
   * @param iClusterName Cluster name, or null for *
   * @param iExclude Node to exclude
   */
  public List<String> getServers(final String iClusterName, final String iExclude) {

    final List<String> serverList = getClusterConfiguration(iClusterName).field(SERVERS);
    if (serverList != null) {
      // COPY AND REMOVE ANY NEW_NODE_TAG
      List<String> filteredServerList = new ArrayList<String>(serverList.size());
      for (String s : serverList) {
        if (!s.equals(NEW_NODE_TAG) && (iExclude == null || !iExclude.equals(s)))
          filteredServerList.add(s);
      }
      return filteredServerList;
    }
    return Collections.EMPTY_LIST;
  }

  /**
   * Returns an ordered list of master server. The first in the list is the first found in
   * configuration. This is used to determine the cluster leader.
   */
  public List<String> getMasterServers() {
    final List<String> serverList = getClusterConfiguration(null).field(SERVERS);
    if (serverList != null) {
      // COPY AND REMOVE ANY NEW_NODE_TAG
      List<String> masters = new ArrayList<String>(serverList.size());
      for (String s : serverList) {
        if (!s.equals(NEW_NODE_TAG)) masters.add(s);
      }

      final ROLES defRole = getDefaultServerRole();

      final ODocument servers = configuration.field(SERVERS);
      if (servers != null) {
        for (Iterator<String> it = masters.iterator(); it.hasNext(); ) {
          final String server = it.next();
          final String roleAsString = servers.field(server);
          final ROLES role =
              roleAsString != null
                  ? ROLES.valueOf(roleAsString.toUpperCase(Locale.ENGLISH))
                  : defRole;
          if (role != ROLES.MASTER) it.remove();
        }
      }

      return masters;
    }

    return Collections.EMPTY_LIST;
  }

  /** Returns the complete list of servers found in configuration. */
  public Set<String> getAllConfiguredServers() {

    final Set<String> servers = new HashSet<String>();

    for (String p : getClusterNames()) {
      final List<String> serverList = getClusterConfiguration(p).field(SERVERS);
      if (serverList != null) {
        for (String s : serverList) if (!s.equals(NEW_NODE_TAG)) servers.add(s);
      }
    }
    return servers;
  }

  /**
   * Returns the set of clusters managed by a server.
   *
   * @param iNodeName Server name
   */
  public Set<String> getClustersOnServer(final String iNodeName) {
    final Set<String> clusters = new HashSet<String>();
    for (String cl : getClusterNames()) {
      final List<String> servers = getServers(cl, null);
      if (servers.contains(iNodeName)) clusters.add(cl);
    }
    return clusters;
  }

  /**
   * Returns the set of clusters where server is the owner.
   *
   * @param iNodeName Server name
   */
  public Set<String> getClustersOwnedByServer(final String iNodeName) {
    final Set<String> clusters = new HashSet<String>();
    for (String cl : getClusterNames()) {
      if (iNodeName.equals(getClusterOwner(cl))) clusters.add(cl);
    }
    return clusters;
  }

  /**
   * Returns the owner server for the given cluster excluding the passed node. The Owner server is
   * the first in server list.
   *
   * @param iClusterName Cluster name, or null for *
   */
  public String getClusterOwner(final String iClusterName) {
    String owner;

    final ODocument clusters = getConfiguredClusters();

    // GET THE CLUSTER CFG
    final ODocument cfg = iClusterName != null ? (ODocument) clusters.field(iClusterName) : null;

    if (cfg != null) {
      owner = cfg.field(OWNER);
      if (owner != null) return owner;

      final List<String> serverList = cfg.field(SERVERS);
      if (serverList != null && !serverList.isEmpty()) {
        // RETURN THE FIRST ONE
        owner = serverList.get(0);
        if (NEW_NODE_TAG.equals(owner) && serverList.size() > 1)
          // DON'T RETURN <NEW_NODE>
          owner = serverList.get(1);
      }
    } else
      // RETURN THE OWNER OF *
      return getClusterOwner(ALL_WILDCARD);

    return owner;
  }

  /**
   * Returns the static owner server for the given cluster.
   *
   * @param iClusterName Cluster name, or null for *
   */
  public String getConfiguredClusterOwner(final String iClusterName) {

    String owner = null;

    final ODocument clusters = getConfiguredClusters();

    // GET THE CLUSTER CFG
    final ODocument cfg = clusters.field(iClusterName);
    if (cfg != null) owner = cfg.field(OWNER);

    return owner;
  }

  /**
   * Returns the configured server list for the requested cluster.
   *
   * @param iClusterName Cluster name, or null for *
   */
  public List<String> getConfiguredServers(final String iClusterName) {

    final Collection<? extends String> list =
        (Collection<? extends String>) getClusterConfiguration(iClusterName).field(SERVERS);
    return list != null ? new ArrayList<String>(list) : null;
  }

  /** Returns the array of configured clusters */
  public String[] getClusterNames() {
    final ODocument clusters = configuration.field(CLUSTERS);
    return clusters.fieldNames();
  }

  /** Returns the default server role between MASTER (default) and REPLICA. */
  public ROLES getDefaultServerRole() {

    final ODocument servers = configuration.field(SERVERS);
    if (servers == null)
      // DEFAULT: MASTER
      return ROLES.MASTER;

    final String role = servers.field(ALL_WILDCARD);
    if (role == null)
      // DEFAULT: MASTER
      return ROLES.MASTER;

    return ROLES.valueOf(role.toUpperCase(Locale.ENGLISH));
  }

  /** Returns the server role between MASTER (default) and REPLICA. */
  public ROLES getServerRole(final String iServerName) {

    final ODocument servers = configuration.field(SERVERS);
    if (servers == null)
      // DEFAULT: MASTER
      return ROLES.MASTER;

    String role = servers.field(iServerName);
    if (role == null) {
      // DEFAULT: MASTER
      role = servers.field(ALL_WILDCARD);
      if (role == null)
        // DEFAULT: MASTER
        return ROLES.MASTER;
    }

    return ROLES.valueOf(role.toUpperCase(Locale.ENGLISH));
  }

  /** Returns the registered servers. */
  public Set<String> getRegisteredServers() {

    final ODocument servers = configuration.field(SERVERS);
    final Set<String> result = new HashSet<String>();
    if (servers != null) for (String s : servers.fieldNames()) result.add(s);
    return result;
  }

  public ODocument getDocument() {
    return configuration;
  }

  /** Returns all the configured data centers' names, if any. */
  public Set<String> getDataCenters() {

    final ODocument dcs = configuration.field(DCS);
    if (dcs == null) return Collections.EMPTY_SET;

    final Set<String> result = new HashSet<String>();
    for (String dc : dcs.fieldNames()) {
      result.add(dc);
    }
    return result;
  }

  /**
   * Returns the data center write quorum.
   *
   * @param dataCenter Data center name
   */
  public int getDataCenterWriteQuorum(final String dataCenter) {

    final ODocument dc = getDataCenterConfiguration(dataCenter);

    Object wq = dc.field(WRITE_QUORUM);
    if (wq instanceof String) {
      if (wq.toString().equalsIgnoreCase(ODistributedConfiguration.QUORUM_MAJORITY)) {
        final List<String> servers = dc.field(SERVERS);
        wq = servers.size() / 2 + 1;
      } else if (wq.toString().equalsIgnoreCase(ODistributedConfiguration.QUORUM_ALL)) {
        final List<String> servers = dc.field(SERVERS);
        wq = servers.size();
      }
    }

    return (Integer) wq;
  }

  /**
   * Returns true if the database is sharded across servers. False if it's completely replicated.
   */
  public boolean isSharded() {

    final ODocument allCluster = getClusterConfiguration(ALL_WILDCARD);
    if (allCluster != null) {
      final List<String> allServers = allCluster.field(SERVERS);
      if (allServers != null && !allServers.isEmpty()) {
        for (String cl : getClusterNames()) {
          final List<String> servers = getServers(cl, null);
          if (servers != null && !servers.isEmpty() && !allServers.containsAll(servers))
            return false;
        }
      }
    }
    return false;
  }

  /**
   * Returns the list of servers in a data center.
   *
   * @param dataCenter Data center name
   * @throws OConfigurationException if the list of servers is not found in data center
   *     configuration
   */
  public List<String> getDataCenterServers(final String dataCenter) {

    final ODocument dc = getDataCenterConfiguration(dataCenter);

    final List<String> servers = dc.field(SERVERS);
    if (servers == null || servers.isEmpty())
      throw new OConfigurationException(
          "Data center '"
              + dataCenter
              + "' does not contain any server in distributed database configuration");

    return new ArrayList<String>(servers);
  }

  /**
   * Returns the data center where the server belongs.
   *
   * @param server Server name
   */
  public String getDataCenterOfServer(final String server) {

    final ODocument dcs = configuration.field(DCS);
    if (dcs != null) {
      for (String dc : dcs.fieldNames()) {
        final ODocument dcConfig = dcs.field(dc);
        if (dcConfig != null) {
          final List<String> dcServers = dcConfig.field("servers");
          if (dcServers != null && !dcServers.isEmpty()) {
            if (dcServers.contains(server))
              // FOUND
              return dc;
          }
        }
      }
    }

    // NOT FOUND
    return null;
  }

  public int getVersion() {
    final Integer v = configuration.field(VERSION);
    if (v == null) return 1;
    return v;
  }

  /** Returns true if the global write quorum is "localDataCenter". */
  public boolean isLocalDataCenterWriteQuorum() {
    return QUORUM_LOCAL_DC.equals(configuration.field(WRITE_QUORUM));
  }

  /**
   * Returns the global read quorum.
   *
   * @param iClusterName Cluster name, or null for *
   */
  public Object getGlobalReadQuorum(final String iClusterName) {
    Object value = getClusterConfiguration(iClusterName).field(READ_QUORUM);
    if (value == null) value = configuration.field(READ_QUORUM);
    return value;
  }

  /**
   * Returns the read quorum.
   *
   * @param clusterName Cluster name, or null for *
   * @param totalConfiguredServers Total node available
   */
  public int getReadQuorum(
      final String clusterName, final int totalConfiguredServers, final String server) {
    return getQuorum(
        "readQuorum", clusterName, totalConfiguredServers, DEFAULT_READ_QUORUM, server);
  }

  /**
   * Returns the write quorum.
   *
   * @param clusterName Cluster name, or null for *
   * @param totalConfiguredMasterServers Total node available
   */
  public int getWriteQuorum(
      final String clusterName, final int totalConfiguredMasterServers, final String server) {
    Integer overWrite = overwriteWriteQuorum.get();
    if (overWrite != null) return overWrite.intValue();
    else
      return getQuorum(
          "writeQuorum", clusterName, totalConfiguredMasterServers, DEFAULT_WRITE_QUORUM, server);
  }

  private ODocument getConfiguredClusters() {
    final ODocument clusters = configuration.field(CLUSTERS);
    if (clusters == null)
      throw new OConfigurationException(
          "Cannot find '" + CLUSTERS + "' in distributed database configuration");
    return clusters;
  }

  @Override
  public String toString() {
    return configuration.toString();
  }

  /**
   * Gets the document representing the cluster configuration.
   *
   * @param iClusterName Cluster name, or null for *
   * @return Always a ODocument
   * @throws OConfigurationException in case "clusters" field is not found in configuration
   */
  protected ODocument getClusterConfiguration(String iClusterName) {
    final ODocument clusters = getConfiguredClusters();

    if (iClusterName == null) iClusterName = ALL_WILDCARD;

    final ODocument cfg;
    if (!clusters.containsField(iClusterName))
      // NO CLUSTER IN CFG: GET THE DEFAULT ONE
      cfg = clusters.field(ALL_WILDCARD);
    else
      // GET THE CLUSTER CFG
      cfg = clusters.field(iClusterName);

    if (cfg == null) return new ODocument();

    return cfg;
  }

  /**
   * Gets the document representing the dc configuration.
   *
   * @param dataCenter Data center name
   * @return Always a ODocument
   * @throws OConfigurationException if the data center configuration is not found
   */
  private ODocument getDataCenterConfiguration(final String dataCenter) {
    final ODocument dcs = configuration.field(DCS);
    if (dcs != null) return dcs.field(dataCenter);
    throw new OConfigurationException(
        "Cannot find the data center '" + dataCenter + "' in distributed database configuration");
  }

  public void forceWriteQuorum(int quorum) {
    overwriteWriteQuorum.set(quorum);
  }

  public void clearForceWriteQuorum() {
    overwriteWriteQuorum.remove();
  }

  /**
   * Returns the read quorum.
   *
   * @param iClusterName Cluster name, or null for *
   * @param totalServers Total nodes available
   */
  private int getQuorum(
      final String quorumSetting,
      final String iClusterName,
      final int totalServers,
      final Object defaultValue,
      final String server) {
    Object value = getClusterConfiguration(iClusterName).field(quorumSetting);
    if (value == null) {
      value = configuration.field(quorumSetting);
      if (value == null) {
        OLogManager.instance()
            .warn(
                this,
                "%s setting not found for cluster=%s in distributed-config.json",
                quorumSetting,
                iClusterName);
        value = defaultValue;
      }
    }

    if (value instanceof String) {
      if (value.toString().equalsIgnoreCase(QUORUM_MAJORITY)) value = totalServers / 2 + 1;
      else if (value.toString().equalsIgnoreCase(QUORUM_ALL)) value = totalServers;
      else if (value.toString().equalsIgnoreCase(QUORUM_LOCAL_DC)) {
        final String dc = getDataCenterOfServer(server);
        if (dc == null)
          throw new OConfigurationException(
              "Data center not specified for server '" + server + "' in distributed configuration");
        value = getDataCenterWriteQuorum(dc);
      } else
        throw new OConfigurationException(
            "The value '"
                + value
                + "' is not supported for "
                + quorumSetting
                + " in distributed configuration");
    }

    return (Integer) value;
  }
}
