src/org/objectweb/cjdbc/controller/loadbalancer/raidb1/RAIDb1ec.java

説明を見る。

package org.objectweb.cjdbc.controller.loadbalancer.raidb1;

import java.sql.SQLException;
import java.util.ArrayList;

import org.objectweb.cjdbc.common.i18n.Translate;
import org.objectweb.cjdbc.common.log.Trace;
import org.objectweb.cjdbc.common.xml.DatabasesXmlTags;
import org.objectweb.cjdbc.controller.backend.DatabaseBackend;
import org.objectweb.cjdbc.controller.loadbalancer.BackendWorkerThread;
import org.objectweb.cjdbc.controller.loadbalancer.policies.WaitForCompletionPolicy;
import org.objectweb.cjdbc.controller.loadbalancer.policies.errorchecking.ErrorCheckingPolicy;
import org.objectweb.cjdbc.controller.loadbalancer.tasks.KillThreadTask;
import org.objectweb.cjdbc.controller.virtualdatabase.VirtualDatabase;

public abstract class RAIDb1ec extends RAIDb1
{
  /*
   * How the code is organized ? 1. Member variables 2. Constructor(s) 3.
   * Request handling 4. Transaction handling 5. Backend management
   */

  protected ArrayList           backendReadThreads;
  protected int                 nbOfConcurrentReads;
  protected ErrorCheckingPolicy errorCheckingPolicy;

  protected static Trace        logger = Trace
                                           .getLogger("org.objectweb.cjdbc.controller.loadbalancer.RAIDb1ec");

  /*
   * Constructors
   */

  public RAIDb1ec(VirtualDatabase vdb,
      WaitForCompletionPolicy waitForCompletionPolicy,
      ErrorCheckingPolicy errorCheckingPolicy, int nbOfConcurrentReads)
      throws SQLException
  {
    super(vdb, waitForCompletionPolicy);
    backendReadThreads = new ArrayList();
    this.errorCheckingPolicy = errorCheckingPolicy;
    this.nbOfConcurrentReads = nbOfConcurrentReads;
  }

  /*
   * Backends management
   */

  public void enableBackend(DatabaseBackend db, boolean writeEnabled)
      throws SQLException
  {
    // Create 2 worker threads for writes
    BackendWorkerThread blockingThread = new BackendWorkerThread(db, this);
    BackendWorkerThread nonBlockingThread = new BackendWorkerThread(db, this);

    // Add first to the blocking thread list
    try
    {
      backendBlockingThreadsRWLock.acquireWrite();
    }
    catch (InterruptedException e)
    {
      String msg = Translate.get(
          "loadbalancer.backendlist.acquire.writelock.failed", e);
      logger.error(msg);
      throw new SQLException(msg);
    }
    backendBlockingThreads.add(blockingThread);
    backendBlockingThreadsRWLock.releaseWrite();
    blockingThread.start();
    logger.info(Translate.get("loadbalancer.backend.workerthread.blocking.add",
        db.getName()));

    // Then add to the non-blocking thread list
    try
    {
      backendNonBlockingThreadsRWLock.acquireWrite();
    }
    catch (InterruptedException e)
    {
      String msg = Translate.get(
          "loadbalancer.backendlist.acquire.writelock.failed", e);
      logger.error(msg);
      throw new SQLException(msg);
    }
    backendNonBlockingThreads.add(nonBlockingThread);
    backendNonBlockingThreadsRWLock.releaseWrite();
    nonBlockingThread.start();
    logger.info(Translate.get(
        "loadbalancer.backend.workerthread.non.blocking.add", db.getName()));

    if (!db.isInitialized())
      db.initializeConnections();
    db.enableRead();
    if (writeEnabled)
      db.enableWrite();
  }

  public synchronized void disableBackend(DatabaseBackend db)
      throws SQLException
  {
    int nbOfThreads = backendBlockingThreads.size();

    // Find the right blocking thread
    for (int i = 0; i < nbOfThreads; i++)
    {
      BackendWorkerThread thread = (BackendWorkerThread) backendBlockingThreads
          .get(i);
      if (thread.getBackend().equals(db))
      {
        logger.info(Translate.get(
            "loadbalancer.backend.workerthread.blocking.remove", db.getName()));

        // Remove it from the backendBlockingThread list
        try
        {
          backendBlockingThreadsRWLock.acquireWrite();
        }
        catch (InterruptedException e)
        {
          String msg = Translate.get(
              "loadbalancer.backendlist.acquire.writelock.failed", e);
          logger.error(msg);
          throw new SQLException(msg);
        }
        backendBlockingThreads.remove(thread);
        backendBlockingThreadsRWLock.releaseWrite();

        synchronized (thread)
        {
          // Kill the thread
          thread.addPriorityTask(new KillThreadTask(1, 1));
          thread.notify();
        }
        break;
      }
    }

    // Find the right non-blocking thread
    nbOfThreads = backendNonBlockingThreads.size();
    for (int i = 0; i < nbOfThreads; i++)
    {
      BackendWorkerThread thread = (BackendWorkerThread) backendNonBlockingThreads
          .get(i);
      if (thread.getBackend().equals(db))
      {
        logger.info(Translate.get(
            "loadbalancer.backend.workerthread.non.blocking.remove", db
                .getName()));

        // Remove it from the backendNonBlockingThreads list
        try
        {
          backendNonBlockingThreadsRWLock.acquireWrite();
        }
        catch (InterruptedException e)
        {
          String msg = Translate.get(
              "loadbalancer.backendlist.acquire.writelock.failed", e);
          logger.error(msg);
          throw new SQLException(msg);
        }
        backendNonBlockingThreads.remove(thread);
        backendNonBlockingThreadsRWLock.releaseWrite();

        synchronized (thread)
        {
          // Kill the thread
          thread.addPriorityTask(new KillThreadTask(1, 1));
          thread.notify();
        }
        break;
      }
    }

    db.disable();
    if (db.isInitialized())
      db.finalizeConnections();
  }

  public String getXmlImpl()
  {
    StringBuffer info = new StringBuffer();
    info.append("<" + DatabasesXmlTags.ELT_RAIDb_1ec + " "
        + DatabasesXmlTags.ATT_nbOfConcurrentReads + "=\""
        + this.nbOfConcurrentReads + "\">");
    this.getRaidb1Xml();
    if (waitForCompletionPolicy != null)
      info.append(waitForCompletionPolicy.getXml());
    info.append("</" + DatabasesXmlTags.ELT_RAIDb_1ec + ">");
    return info.toString();
  }
}

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