src/org/objectweb/cjdbc/controller/loadbalancer/tasks/SelectRequestTask.java

説明を見る。

package org.objectweb.cjdbc.controller.loadbalancer.tasks;

import java.sql.Connection;
import java.sql.SQLException;

import org.objectweb.cjdbc.common.exceptions.UnreachableBackendException;
import org.objectweb.cjdbc.common.sql.SelectRequest;
import org.objectweb.cjdbc.common.util.Constants;
import org.objectweb.cjdbc.controller.backend.DatabaseBackend;
import org.objectweb.cjdbc.controller.connection.AbstractConnectionManager;
import org.objectweb.cjdbc.controller.loadbalancer.AbstractLoadBalancer;
import org.objectweb.cjdbc.controller.loadbalancer.BackendWorkerThread;
import org.objectweb.cjdbc.controller.virtualdatabase.ControllerResultSet;

public class SelectRequestTask extends AbstractTask
{
  private SelectRequest       request;
  private ControllerResultSet result;

  public SelectRequestTask(int nbToComplete, int totalNb, SelectRequest request)
  {
    super(nbToComplete, totalNb);
    this.request = request;
  }

  public void execute(BackendWorkerThread backendThread) throws SQLException
  {
    DatabaseBackend backend = backendThread.getBackend();

    AbstractConnectionManager cm = backend.getConnectionManager(request
        .getLogin());
    if (cm == null)
    {
      SQLException se = new SQLException(
          "No Connection Manager for Virtual Login:" + request.getLogin());
      try
      {
        notifyFailure(backendThread, 1, se);
      }
      catch (SQLException ignore)
      {

      }
      throw se;
    }

    if (request.isAutoCommit())
    { // Use a connection just for this request
      Connection c = null;
      try
      {
        c = cm.getConnection();
      }
      catch (UnreachableBackendException e1)
      {
        SQLException se = new SQLException("Backend " + backend.getName()
            + " is no more reachable.");
        try
        {
          notifyFailure(backendThread, 1, se);
        }
        catch (SQLException ignore)
        {
        }
        backendThread.getLogger().error(
            "Disabling backend " + backend.getName()
                + " because it is no more reachable.");
        backend.disable();
        throw se;
      }

      // Sanity check
      if (c == null)
      {
        SQLException se = new SQLException("No more connections");
        try
        { // All backends failed, just ignore
          if (!notifyFailure(backendThread, (long) request.getTimeout() * 1000,
              se))
            return;
        }
        catch (SQLException ignore)
        {
        }
        // Disable this backend (it is no more in sync) by killing the backend
        // thread
        backendThread.kill();
        throw new SQLException("Request '"
            + request.getSQLShortForm(Constants.SQL_SHORT_FORM_LENGTH)
            + "' failed on backend " + backend.getName() + " (" + se + ")");
      }

      // Execute Query
      try
      {
        result = AbstractLoadBalancer.executeSelectRequestOnBackend(request,
            backend, c, null);
      }
      catch (Exception e)
      {
        try
        { // All backends failed, just ignore
          if (!notifyFailure(backendThread, (long) request.getTimeout() * 1000,
              e))
            return;
        }
        catch (SQLException ignore)
        {
        }
        throw new SQLException("Request '"
            + request.getSQLShortForm(Constants.SQL_SHORT_FORM_LENGTH)
            + "' failed on backend " + backend.getName() + " (" + e + ")");
      }
      finally
      {
        cm.releaseConnection(c);
      }
    }
    else
    {
      Connection c;
      long tid = request.getTransactionId();
      Long lTid = new Long(tid);

      if (!backend.isStartedTransaction(lTid))
      { // Transaction has not been started yet, this is a lazy begin
        try
        {
          c = cm.getConnection(tid);
        }
        catch (UnreachableBackendException e1)
        {
          SQLException se = new SQLException("Backend " + backend.getName()
              + " is no more reachable.");
          try
          {
            notifyFailure(backendThread, 1, se);
          }
          catch (SQLException ignore)
          {
          }
          backendThread.getLogger().error(
              "Disabling backend " + backend.getName()
                  + " because it is no more reachable.");
          backend.disable();
          throw se;
        }

        // Sanity check
        if (c == null)
        { // Bad connection
          SQLException se = new SQLException(
              "Unable to get connection for transaction " + tid);
          try
          { // All backends failed, just ignore
            if (!notifyFailure(backendThread,
                (long) request.getTimeout() * 1000, se))
              return;
          }
          catch (SQLException ignore)
          {
          }
          // Disable this backend (it is no more in sync) by killing the
          // backend thread
          backendThread.kill();
          String msg = "Request '"
              + request.getSQLShortForm(backend.getSQLShortFormLength())
              + "' failed on backend " + backend.getName() + " but "
              + getSuccess() + " succeeded (" + se + ")";
          backendThread.getLogger().error(msg);
          throw new SQLException(msg);
        }

        // begin transaction
        backend.startTransaction(lTid);
        c.setAutoCommit(false);
      }
      else
      { // Transaction has already been started, retrieve connection
        c = cm.retrieveConnection(tid);

        // Sanity check
        if (c == null)
        { // Bad connection
          SQLException se = new SQLException(
              "Unable to retrieve connection for transaction " + tid);
          try
          { // All backends failed, just ignore
            if (!notifyFailure(backendThread,
                (long) request.getTimeout() * 1000, se))
              return;
          }
          catch (SQLException ignore)
          {
          }
          // Disable this backend (it is no more in sync) by killing the
          // backend thread
          backendThread.kill();
          String msg = "Request '"
              + request.getSQLShortForm(backend.getSQLShortFormLength())
              + "' failed on backend " + backend.getName() + " but "
              + getSuccess() + " succeeded (" + se + ")";
          backendThread.getLogger().error(msg);
          throw new SQLException(msg);
        }
      }
      // Execute Query
      try
      {
        result = AbstractLoadBalancer.executeSelectRequestOnBackend(request,
            backend, c, null);
      }
      catch (Exception e)
      {
        try
        { // All backends failed, just ignore
          if (!notifyFailure(backendThread, (long) request.getTimeout() * 1000,
              e))
            return;
        }
        catch (SQLException ignore)
        {
        }
        throw new SQLException("Request '"
            + request.getSQLShortForm(Constants.SQL_SHORT_FORM_LENGTH)
            + "' failed on backend " + backend.getName() + " (" + e + ")");
      }
    }
    notifySuccess();
  }

  public ControllerResultSet getResult()
  {
    return result;
  }

  public String toString()
  {
    return "SelectRequestTask (" + request.getSQL() + ")";
  }
}

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