OPENDJ-2154 (CR-7325) search on cn=monitor changenumber index database time...

Jean-Noel Rouvignac

19.09.2015 3794b2a11e287845176b0a4b849725af2d992019

OPENDJ-2154 (CR-7325) search on cn=monitor changenumber index database times out


With a very large changelogDb, when issuing queries on cn=monitor, the code counts the number of entries in the changeNumberIndexDb. In order to do the count, it cursors through the changeNumberIndexDb, decoding each and every change in the changeNumberIndexDb.
This is a killer with very large changelogDb.
Any query on cn=monitor with very large file-based changelogDb is now at risk to timeout.

JE has a direct API to count the number of records in a tree.
File based changelog does not have such API, thus, a first implementation was to count the changes by cursoring through the changeNumberIndexDb.
However, since the changeNumberIndexDb purge has been reimplemented, there are no longer "holes" in the changeNumbers. As a consequence, a simple way to count the number of changes is to do "newestChangeNumber - oldestChangeNumber".



FileChangeNumberIndexDB.java:
In DbMonitorProvider.getMonitorData(), changed the code to make a diff between first and last changeNumber.
Introduced ChangeNumberType enum to get rid of unreadable boolean parameter.
Extracted toAttribute() from createChangeNumberAttribute().

 opendj-server-legacy/src/main/java/org/opends/server/replication/server/changelog/file/FileChangeNumberIndexDB.java

@@ -21,10 +21,12 @@
 * CDDL HEADER END
 *
 *
 *      Copyright 2014 ForgeRock AS
 *      Copyright 2014-2015 ForgeRock AS
 */
package org.opends.server.replication.server.changelog.file;

import static org.opends.messages.ReplicationMessages.*;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
@@ -39,10 +41,14 @@
import org.opends.server.api.MonitorProvider;
import org.opends.server.core.DirectoryServer;
import org.opends.server.replication.common.CSN;
import org.opends.server.replication.server.changelog.api.*;
import org.opends.server.types.*;

import static org.opends.messages.ReplicationMessages.*;
import org.opends.server.replication.server.changelog.api.ChangeNumberIndexDB;
import org.opends.server.replication.server.changelog.api.ChangeNumberIndexRecord;
import org.opends.server.replication.server.changelog.api.ChangelogException;
import org.opends.server.replication.server.changelog.api.DBCursor;
import org.opends.server.types.Attribute;
import org.opends.server.types.Attributes;
import org.opends.server.types.DN;
import org.opends.server.types.InitializationException;

/**
 * Implementation of a ChangeNumberIndexDB with a log.
@@ -52,14 +58,27 @@
 */
class FileChangeNumberIndexDB implements ChangeNumberIndexDB
{
  /** The type of the required change number. */
  private static enum ChangeNumberType
  {
    FIRST("first-draft-changenumber"), LAST("last-draft-changenumber");

    private final String attrName;

    private ChangeNumberType(String attrName)
    {
      this.attrName = attrName;
    }

    private String getAttributeName()
    {
      return this.attrName;
    }
  }

  private static final LocalizedLogger logger = LocalizedLogger.getLoggerForThisClass();

  private static final int NO_KEY = 0;

  /** The parser of records stored in this ChangeNumberIndexDB. */
  static final RecordParser<Long, ChangeNumberIndexRecord> RECORD_PARSER = new ChangeNumberIndexDBParser();

  static final Record.Mapper<ChangeNumberIndexRecord, CSN> MAPPER_TO_CSN =
  private static final Record.Mapper<ChangeNumberIndexRecord, CSN> MAPPER_TO_CSN =
      new Record.Mapper<ChangeNumberIndexRecord, CSN>()
      {
        @Override
@@ -68,6 +87,8 @@
          return value.getCSN();
        }
      };
  /** The parser of records stored in this ChangeNumberIndexDB. */
  static final RecordParser<Long, ChangeNumberIndexRecord> RECORD_PARSER = new ChangeNumberIndexDBParser();

  /** The log in which records are persisted. */
  private final Log<Long, ChangeNumberIndexRecord> log;
@@ -251,43 +272,33 @@
    return null;
  }

  /**
   * Implements the Monitoring capabilities of the FileChangeNumberIndexDB.
   */
  /** Implements the Monitoring capabilities of the FileChangeNumberIndexDB. */
  private class DbMonitorProvider extends MonitorProvider<MonitorProviderCfg>
  {
    /** {@inheritDoc} */
    @Override
    public List<Attribute> getMonitorData()
    {
      long firstCN = readChangeNumber(ChangeNumberType.FIRST);
      long lastCN = readChangeNumber(ChangeNumberType.LAST);
      long numberOfChanges = lastCN == NO_KEY ? 0 : lastCN - firstCN + 1;

      final List<Attribute> attributes = new ArrayList<Attribute>();
      attributes.add(createChangeNumberAttribute(true));
      attributes.add(createChangeNumberAttribute(false));
      long numberOfChanges = 0;
      try
      {
         numberOfChanges = count();
      }
      catch (ChangelogException e)
      {
        logger.traceException(e);
      }
      attributes.add(toAttribute(ChangeNumberType.FIRST, firstCN));
      attributes.add(toAttribute(ChangeNumberType.LAST, lastCN));
      attributes.add(Attributes.create("count", Long.toString(numberOfChanges)));
      return attributes;
    }

    private Attribute createChangeNumberAttribute(final boolean isFirst)
    private Attribute toAttribute(final ChangeNumberType cnType, long changeNumber)
    {
      final String attributeName = isFirst ? "first-draft-changenumber" : "last-draft-changenumber";
      final String changeNumber = String.valueOf(readChangeNumber(isFirst));
      return Attributes.create(attributeName, changeNumber);
      return Attributes.create(cnType.getAttributeName(), String.valueOf(changeNumber));
    }

    private long readChangeNumber(final boolean isFirst)
    private long readChangeNumber(final ChangeNumberType type)
    {
      try
      {
        return getChangeNumber(isFirst ? readFirstRecord() : readLastRecord());
        return getChangeNumber(readChangeNumber0(type));
      }
      catch (ChangelogException e)
      {
@@ -296,14 +307,25 @@
      }
    }

    /** {@inheritDoc} */
    private ChangeNumberIndexRecord readChangeNumber0(final ChangeNumberType type) throws ChangelogException
    {
      if (ChangeNumberType.FIRST.equals(type))
      {
        return readFirstRecord();
      }
      else if (ChangeNumberType.LAST.equals(type))
      {
        return readLastRecord();
      }
      throw new IllegalArgumentException("Not implemented for ChangeNumber: " + type);
    }

    @Override
    public String getMonitorInstanceName()
    {
      return "ChangeNumber Index Database";
    }

    /** {@inheritDoc} */
    @Override
    public void initializeMonitorProvider(MonitorProviderCfg configuration)
                            throws ConfigException, InitializationException