Android Open Source - DKO Mirrored Data Source

• Back to Database/orm  ↑

From Project

Back to project page DKO.

License

The source code is released under:

GNU Lesser General Public License

Java Source Code

package org.kered.dko.datasource;
/*  ww  w .ja v a2 s.  c  o  m*/
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Random;
import java.util.logging.Logger;

import javax.sql.DataSource;


/**
 * This class wraps other {@code javax.sql.DataSource} instances.  It usually passes
 * through calls to the primary, but if {@code getMirroredConnection()}
 * is called a random mirror is used instead.
 *
 * @author Derek Anderson
 */
public class MirroredDataSource implements MatryoshkaDataSource {

  private final DataSource primary;
  private DataSource[] mirrors;
  private static final Logger log = Logger.getLogger("org.kered.dko.datasource.MirroredDataSource");

  /**
     * This class usually passes
     * through calls to the primary, but if {@code getMirroredConnection()}
     * is called a random mirror is used instead.
   * @param primary
   * @param mirrors
   */
  public MirroredDataSource(final DataSource primary, final DataSource... mirrors) {
    this.primary = primary;
    if (mirrors == null) this.mirrors = new DataSource[0];
    else this.mirrors = mirrors;
  }

  @Override
  public PrintWriter getLogWriter() throws SQLException {
    return primary.getLogWriter();
  }

  @Override
  public int getLoginTimeout() throws SQLException {
    return primary.getLoginTimeout();
  }

  @Override
  public void setLogWriter(final PrintWriter arg0) throws SQLException {
    primary.setLogWriter(arg0);
  }

  @Override
  public void setLoginTimeout(final int arg0) throws SQLException {
    primary.setLoginTimeout(arg0);
  }

  @Override
  public boolean isWrapperFor(final Class<?> arg0) throws SQLException {
    if (primary.getClass().equals(arg0)) return true;
    return primary.isWrapperFor(arg0);
  }

  @SuppressWarnings("unchecked")
  @Override
  public <T> T unwrap(final Class<T> arg0) throws SQLException {
    if (primary.getClass().equals(arg0)) return (T) primary;
    return primary.unwrap(arg0);
  }

  @Override
  public Connection getConnection() throws SQLException {
    return primary.getConnection();
  }

  /**
   * Returns a connection from a randomly selected mirror. &nbsp;
   * Feel free to override this method to implement other
   * load balancing stratigies in your own code.
   * @return
   * @throws SQLException
   */
  public Connection getMirroredConnection() throws SQLException {
    // for now we randomly select the mirror
    // TODO: implement other strategies
    if (mirrors.length == 0) return getConnection();
    final Random random = new Random();
    final int i = random.nextInt(mirrors.length);
    for (int j=0; j<mirrors.length; ++j) {
      final DataSource mirror = mirrors[(i+j)%mirrors.length];
      try {
        return mirror.getConnection();
      } catch (final SQLException e) {
        // db down - try another
        log.warning("could not connect to "+ mirror +": "+ e.toString());
      }
    }
    try {
      return primary.getConnection();
    } catch (final SQLException e) {
      log.warning("could not connect to "+ primary +": "+ e.toString());
    }
    throw new SQLException("could not connect to any mirror: "
        + Arrays.asList(mirrors) +" or the primary: "+ primary);
  }

  @Override
  public Connection getConnection(final String arg0, final String arg1)
      throws SQLException {
    return primary.getConnection(arg0, arg1);
  }

  @Override
  public String toString() {
    return "[MirroredDataSource primary="+ primary +" mirrors="
        + Util.join(",", mirrors) +"]";
  }

  public DataSource getPrimaryDataSource() {
    return primary;
  }

  //@Override
  public Logger getParentLogger() throws SQLFeatureNotSupportedException {
    throw new SQLFeatureNotSupportedException();
  }

  @Override
  public DataSource getPrimaryUnderlying() {
    return primary;
  }

  @Override
  public Collection<DataSource> getAllUnderlying() {
    final Collection<DataSource> ret = new ArrayList<DataSource>();
    ret.add(primary);
    for (final DataSource mirror : mirrors) ret.add(mirror);
    return ret;
  }
}

Java Source Code List

• Back to Database/orm  ↑