DbusEventBufferWriter.java

package com.linkedin.databus.core.test;
/*
 *
 * Copyright 2013 LinkedIn Corp. All rights reserved
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 *
*/

import java.nio.channels.WritableByteChannel;

import org.apache.log4j.Logger;

import com.linkedin.databus.core.Checkpoint;
import com.linkedin.databus.core.DbusEventBuffer;
import com.linkedin.databus.core.Encoding;
import com.linkedin.databus.core.OffsetNotFoundException;
import com.linkedin.databus.core.ScnNotFoundException;
import com.linkedin.databus.core.StreamEventsArgs;
import com.linkedin.databus.core.monitoring.mbean.DbusEventsStatisticsCollector;
import com.linkedin.databus2.core.filter.AllowAllDbusFilter;

/**
 * Runnable that reads data from a DbusEventBuffer and writes to a channel if any events are found.
 *
 * This class is intended only for testing!
 *
 * @author snagaraj
 */

public class DbusEventBufferWriter implements Runnable
{
  public static final Logger LOG = Logger.getLogger(DbusEventBufferWriter.class.getName());

  public DbusEventBufferWriter(DbusEventBuffer buffer,
                               WritableByteChannel channel,
                               int batchsize,
                               DbusEventsStatisticsCollector stats)
  {
    _channel = channel;
    _buffer = buffer;
    _batchsize = batchsize;
    _stop=false;
    _count=0;
    _expectedEvents = -1;
    _stats = stats;
  }

  @Override
  //run in a thread please;
  public void run()
  {
    _stop = false;
    _expectedEvents = -1;
    _count = 0;
    try {
      Checkpoint cp = new Checkpoint();
      //is there anything from the checkpoint I can infer that it's end of stream? control message?
      cp.setFlexible();
      do {
        int streamedEvents=0;
        StreamEventsArgs args = new StreamEventsArgs(_batchsize).setStatsCollector(_stats);
        while ((streamedEvents = _buffer.streamEvents(cp, _channel, args).getNumEventsStreamed()) > 0) {
          _count += streamedEvents;
        }
        //the writer hangs around - cannot count events; cp provides current window and window offset;
        //and streamedEvents has the count of all events - not just data events
      } while (!_stop &&  !endOfEvents());
    } catch (ScnNotFoundException e) {
      LOG.error("SCN not found! " + e);
    }
    catch (OffsetNotFoundException e) {
      LOG.error("Offset not found! " + e);
    }
    finally {
      _stop = false;
    }
  }

  public void stop()
  {
    _stop = true;
  }

  public long eventsWritten()
  {
    return _count;
  }

  public long expectedEvents()
  {
    return _expectedEvents;
  }

  public void setExpectedEvents(long e)
  {
    _expectedEvents = e;
  }

  private boolean endOfEvents()
  {
    return (_expectedEvents > 0) && (eventsWritten() >= expectedEvents());
  }

  private final WritableByteChannel _channel;
  private final DbusEventBuffer _buffer;
  private final int _batchsize;
  private boolean _stop;
  private long _count;
  private long _expectedEvents;
  private final DbusEventsStatisticsCollector _stats;
}