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Lucene example source code file (NearRealtimeReaderTask.java)

This example Lucene source code file (NearRealtimeReaderTask.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

exception, indexreader, indexreader, indexwriter, nearrealtimereader, nearrealtimereader, nearrealtimereadertask, nearrealtimereadertask, override, override, perfrundata, perftask, runtimeexception

The Lucene NearRealtimeReaderTask.java source code

package org.apache.lucene.benchmark.byTask.tasks;

 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.

import org.apache.lucene.benchmark.byTask.PerfRunData;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.util.ArrayUtil;

 * Spawns a BG thread that periodically (defaults to 3.0
 * seconds, but accepts param in seconds) wakes up and asks
 * IndexWriter for a near real-time reader.  Then runs a
 * single query (body: 1) sorted by docdate, and prints
 * time to reopen and time to run the search.
 * @lucene.experimental It's also not generally usable, eg
 * you cannot change which query is executed.
public class NearRealtimeReaderTask extends PerfTask {

  long pauseMSec = 3000L;

  int reopenCount;
  int[] reopenTimes = new int[1];

  public NearRealtimeReaderTask(PerfRunData runData) {

  public int doLogic() throws Exception {

    final PerfRunData runData = getRunData();

    // Get initial reader
    IndexWriter w = runData.getIndexWriter();
    if (w == null) {
      throw new RuntimeException("please open the writer before invoking NearRealtimeReader");

    if (runData.getIndexReader() != null) {
      throw new RuntimeException("please close the existing reader before invoking NearRealtimeReader");
    long t = System.currentTimeMillis();
    IndexReader r = IndexReader.open(w, true);
    // Transfer our reference to runData

    // TODO: gather basic metrics for reporting -- eg mean,
    // stddev, min/max reopen latencies

    // Parent sequence sets stopNow
    reopenCount = 0;
    while(!stopNow) {
      long waitForMsec = (pauseMSec - (System.currentTimeMillis() - t));
      if (waitForMsec > 0) {
        //System.out.println("NRT wait: " + waitForMsec + " msec");

      t = System.currentTimeMillis();
      final IndexReader newReader = r.reopen();
      if (r != newReader) {
        final int delay = (int) (System.currentTimeMillis()-t);
        if (reopenTimes.length == reopenCount) {
          reopenTimes = ArrayUtil.grow(reopenTimes, 1+reopenCount);
        reopenTimes[reopenCount++] = delay;
        // TODO: somehow we need to enable warming, here
        // Transfer our reference to runData
        r = newReader;
    stopNow = false;

    return reopenCount;

  public void setParams(String params) {
    pauseMSec = (long) (1000.0*Float.parseFloat(params));

  public void close() {
    System.out.println("NRT reopen times:");
    for(int i=0;i<reopenCount;i++) {
      System.out.print(" " + reopenTimes[i]);

  public boolean supportsParams() {
    return true;

Other Lucene examples (source code examples)

Here is a short list of links related to this Lucene NearRealtimeReaderTask.java source code file:

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