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/*
 * Licensed under the GPL License. You may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 *
 * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
 * WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE.
 */
package psiprobe.model.stats;

import com.thoughtworks.xstream.XStream;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;

import javax.inject.Inject;

import org.jfree.data.xy.XYDataItem;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.web.context.WebApplicationContext;

import psiprobe.tools.UpdateCommitLock;

/**
 * The Class StatsCollection.
 */
public class StatsCollection implements InitializingBean, DisposableBean, ApplicationContextAware {

  /** The Constant logger. */
  private static final Logger logger = LoggerFactory.getLogger(StatsCollection.class);

  /** The stats data. */
  private Map> statsData = new TreeMap<>();

  /** The xstream. */
  @Inject
  private XStream xstream;

  /** The swap file name. */
  private String swapFileName;

  /** The storage path. */
  private String storagePath;

  /** The context temp dir. */
  private File contextTempDir;

  /** The max files. */
  private int maxFiles = 2;

  /** The lock. */
  private final UpdateCommitLock lock = new UpdateCommitLock();

  /**
   * Gets the swap file name.
   *
   * @return the swap file name
   */
  public String getSwapFileName() {
    return swapFileName;
  }

  /**
   * Sets the swap file name.
   *
   * @param swapFileName the new swap file name
   */
  @Value("stats.xml")
  public void setSwapFileName(String swapFileName) {
    this.swapFileName = swapFileName;
  }

  /**
   * Gets the storage path.
   *
   * @return the storage path
   */
  public String getStoragePath() {
    return storagePath;
  }

  /**
   * Sets the storage path. The default location for the stat files is
   * $CALALINA_BASE/work/<hostname>/<context_name>. Use this property to override it.
   *
   * @param storagePath the new storage path
   */
  // TODO We should make this configurable
  public void setStoragePath(String storagePath) {
    this.storagePath = storagePath;
  }

  /**
   * Checks if is collected.
   *
   * @param statsName the stats name
   *
   * @return true, if is collected
   */
  public synchronized boolean isCollected(String statsName) {
    return statsData.get(statsName) != null;
  }

  /**
   * Gets the max files.
   *
   * @return the max files
   */
  public int getMaxFiles() {
    return maxFiles;
  }

  /**
   * Sets the max files.
   *
   * @param maxFiles the new max files
   */
  public void setMaxFiles(int maxFiles) {
    this.maxFiles = maxFiles > 0 ? maxFiles : 2;
  }

  /**
   * New stats.
   *
   * @param name the name
   * @param maxElements the max elements
   *
   * @return the list
   */
  public synchronized List newStats(String name, int maxElements) {
    List stats = Collections.synchronizedList(new ArrayList<>(maxElements));
    statsData.put(name, stats);
    return stats;
  }

  /**
   * Reset stats.
   *
   * @param name the name
   */
  public synchronized void resetStats(String name) {
    List stats = getStats(name);
    if (stats != null) {
      stats.clear();
    }
  }

  /**
   * Gets the stats.
   *
   * @param name the name
   *
   * @return the stats
   */
  public synchronized List getStats(String name) {
    return statsData.get(name);
  }

  /**
   * Gets the last value for stat.
   *
   * @param statName the stat name
   *
   * @return the last value for stat
   */
  public long getLastValueForStat(String statName) {
    long statValue = 0;

    List stats = getStats(statName);
    if (stats != null && !stats.isEmpty()) {
      XYDataItem xy = stats.get(stats.size() - 1);
      if (xy != null && xy.getY() != null) {
        statValue = xy.getY().longValue();
      }
    }

    return statValue;
  }

  /**
   * Returns series if stat name starts with the prefix.
   *
   * @param statNamePrefix they key under which the stats are stored
   *
   * @return a Map of matching stats. Map keys are stat names and map values are corresponding
   *         series.
   */
  public synchronized Map> getStatsByPrefix(String statNamePrefix) {
    Map> map = new HashMap<>();
    for (Map.Entry> en : statsData.entrySet()) {
      if (en.getKey().startsWith(statNamePrefix)) {
        map.put(en.getKey(), en.getValue());
      }
    }
    return map;
  }

  /**
   * Make file.
   *
   * @return the file
   */
  private File makeFile() {
    return storagePath == null ? new File(contextTempDir, swapFileName)
        : new File(storagePath, swapFileName);
  }

  /**
   * Shift files.
   *
   * @param index the index
   */
  private void shiftFiles(int index) {
    if (index >= maxFiles - 1) {
      try {
        if (Files.exists(Paths.get(makeFile().getAbsolutePath() + "." + index))) {
          Files.delete(Paths.get(makeFile().getAbsolutePath() + "." + index));
        }
      } catch (IOException e) {
        logger.error("Could not delete file {}",
            new File(makeFile().getAbsolutePath() + "." + index).getName());
      }
    } else {
      shiftFiles(index + 1);
      File srcFile = index == 0 ? makeFile() : new File(makeFile().getAbsolutePath() + "." + index);
      if (Files.exists(srcFile.toPath())) {
        File destFile = new File(makeFile().getAbsolutePath() + "." + (index + 1));
        if (!srcFile.renameTo(destFile)) {
          logger.error("Could not rename file {} to {}", srcFile.getName(), destFile.getName());
        }
      }
    }
  }

  /**
   * Writes stats data to file on disk.
   *
   * @throws InterruptedException if a lock cannot be obtained
   */
  public synchronized void serialize() throws InterruptedException {
    lock.lockForCommit();
    long start = System.currentTimeMillis();
    try {
      shiftFiles(0);
      try (OutputStream os = Files.newOutputStream(makeFile().toPath())) {
        xstream.toXML(statsData, os);
      }
    } catch (Exception e) {
      logger.error("Could not write stats data to '{}'", makeFile().getAbsolutePath(), e);
    } finally {
      lock.releaseCommitLock();
      logger.debug("stats serialized in {}ms", System.currentTimeMillis() - start);
    }
  }

  /**
   * Deserialize.
   *
   * @param file the file
   *
   * @return the map
   */
  @SuppressWarnings("unchecked")
  private Map> deserialize(File file) {
    Map> stats = null;
    if (file.exists() && file.canRead()) {
      long start = System.currentTimeMillis();
      try {
        try (InputStream fis = Files.newInputStream(file.toPath())) {
          stats = (Map>) xstream.fromXML(fis);

          if (stats != null) {
            // adjust stats data so that charts look realistic.
            // we do that by ending the previous stats group with 0 value
            // and starting the current stats group also with 0
            // thus giving the chart nice plunge to zero indicating downtime
            // and lets not bother about rotating stats;
            // regular stats collection cycle will do it

            for (Entry> set : stats.entrySet()) {
              List list = set.getValue();
              if (!list.isEmpty()) {
                XYDataItem xy = list.get(list.size() - 1);
                list.add(new XYDataItem(xy.getX().longValue() + 1, 0));
                list.add(new XYDataItem(System.currentTimeMillis(), 0));
              }
            }
          }
        }
        logger.debug("stats data read in {}ms", System.currentTimeMillis() - start);
      } catch (ExceptionInInitializerError e) {
        if (e.getCause() != null && e.getCause().getMessage() != null && e.getCause().getMessage()
            .contains("does not \"opens java.util\" to unnamed module")) {
          logger.error(
              "Stats deserialization disabled, use '--add-opens java.base/java.util=ALL-UNNAMED' to start Tomcat to enable again");
        } else {
          logger.error("Could not read stats data from '{}' during initialization",
              file.getAbsolutePath(), e);
        }
      } catch (Exception e) {
        logger.error("Could not read stats data from '{}'", file.getAbsolutePath(), e);
      }
    }

    return stats;
  }

  /**
   * Lock for update.
   *
   * @throws InterruptedException the interrupted exception
   */
  public void lockForUpdate() throws InterruptedException {
    lock.lockForUpdate();
  }

  /**
   * Release lock.
   */
  public void releaseLock() {
    lock.releaseUpdateLock();
  }

  /**
   * Reads stats data from file on disk.
   */
  @Override
  public synchronized void afterPropertiesSet() {
    int index = 0;
    Map> stats;

    while (true) {
      File file = index == 0 ? makeFile() : new File(makeFile().getAbsolutePath() + "." + index);
      stats = deserialize(file);
      index += 1;
      if (stats != null || index >= maxFiles - 1) {
        break;
      }
    }

    if (stats != null) {
      statsData = stats;
    } else {
      logger.debug("Stats data file not found. Empty file assumed.");
    }

  }

  @Override
  public void destroy() throws Exception {
    serialize();
  }

  @Override
  public void setApplicationContext(ApplicationContext applicationContext) {
    WebApplicationContext wac = (WebApplicationContext) applicationContext;
    contextTempDir = (File) wac.getServletContext().getAttribute("javax.servlet.context.tempdir");
  }

}




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