src/org/objectweb/cjdbc/controller/loadbalancer/policies/createtable/CreateTableRoundRobin.java

説明を見る。

package org.objectweb.cjdbc.controller.loadbalancer.policies.createtable;

import java.util.ArrayList;

import org.objectweb.cjdbc.controller.backend.DatabaseBackend;

public class CreateTableRoundRobin extends CreateTableRule
{
  private int index = 0;

  public CreateTableRoundRobin()
  {
    super(CreateTablePolicy.ROUND_ROBIN);
  }

  public CreateTableRoundRobin(ArrayList backendList)
  {
    super(CreateTablePolicy.ROUND_ROBIN, backendList);
  }

  public ArrayList getBackends(ArrayList backends) throws CreateTableException
  {
    int size = backends.size();

    if (nbOfNodes == 0)
      return null;
    else if (nbOfNodes == size)
      return backends;

    ArrayList clonedList;

    if (backendList.size() > 0)
    { // Keep only the backends that are affected by this rule
      clonedList = new ArrayList(nbOfNodes);
      for (int i = 0; i < size; i++)
      {
        DatabaseBackend db = (DatabaseBackend) backends.get(i);
        if (db.isWriteEnabled() && backendList.contains(db.getName()))
          clonedList.add(db);
      }
    }
    else
    { // Take all enabled backends
      clonedList = new ArrayList(size);
      for (int i = 0; i < size; i++)
      {
        DatabaseBackend db = (DatabaseBackend) backends.get(i);
        if (db.isWriteEnabled())
          clonedList.add(db);
      }
    }

    int clonedSize = clonedList.size();

    if (nbOfNodes == clonedSize)
      return backends;
    else if (nbOfNodes > clonedSize)
      throw new CreateTableException(
        "Asking for more backends ("
          + nbOfNodes
          + ") than available ("
          + clonedSize
          + ")");

    ArrayList result = new ArrayList(nbOfNodes);

    synchronized (this)
    { // index must be modified in mutual exclusion
      for (int i = 0; i < nbOfNodes; i++)
      {
        index = (index + 1) % clonedSize;
        result.add(clonedList.remove(index));
      }
    }

    return result;
  }

  public String getInformation()
  {
    String s;
    if (tableName == null)
      s = "Default rule create table on ";
    else
      s = "Rule for table " + tableName + " create table on ";

    return s + nbOfNodes + " node(s) in round-robin from " + backendList;
  }
}

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