/**
   * Initializes store.
   *
   * @throws GridException If failed to initialize.
   */
  private void init() throws GridException {
    if (initGuard.compareAndSet(false, true)) {
      if (log.isDebugEnabled()) log.debug("Initializing cache store.");

      try {
        if (sesFactory != null)
          // Session factory has been provided - nothing to do.
          return;

        if (!F.isEmpty(hibernateCfgPath)) {
          try {
            URL url = new URL(hibernateCfgPath);

            sesFactory = new Configuration().configure(url).buildSessionFactory();

            if (log.isDebugEnabled()) log.debug("Configured session factory using URL: " + url);

            // Session factory has been successfully initialized.
            return;
          } catch (MalformedURLException e) {
            if (log.isDebugEnabled())
              log.debug("Caught malformed URL exception: " + e.getMessage());
          }

          // Provided path is not a valid URL. File?
          File cfgFile = new File(hibernateCfgPath);

          if (cfgFile.exists()) {
            sesFactory = new Configuration().configure(cfgFile).buildSessionFactory();

            if (log.isDebugEnabled())
              log.debug("Configured session factory using file: " + hibernateCfgPath);

            // Session factory has been successfully initialized.
            return;
          }

          // Provided path is not a file. Classpath resource?
          sesFactory = new Configuration().configure(hibernateCfgPath).buildSessionFactory();

          if (log.isDebugEnabled())
            log.debug("Configured session factory using classpath resource: " + hibernateCfgPath);
        } else {
          if (hibernateProps == null) {
            U.warn(
                log, "No Hibernate configuration has been provided for store (will use default).");

            hibernateProps = new Properties();

            hibernateProps.setProperty("hibernate.connection.url", DFLT_CONN_URL);
            hibernateProps.setProperty("hibernate.show_sql", DFLT_SHOW_SQL);
            hibernateProps.setProperty("hibernate.hbm2ddl.auto", DFLT_HBM2DDL_AUTO);
          }

          Configuration cfg = new Configuration();

          cfg.setProperties(hibernateProps);

          assert resourceAvailable(MAPPING_RESOURCE);

          cfg.addResource(MAPPING_RESOURCE);

          sesFactory = cfg.buildSessionFactory();

          if (log.isDebugEnabled())
            log.debug("Configured session factory using properties: " + hibernateProps);
        }
      } catch (HibernateException e) {
        throw new GridException("Failed to initialize store.", e);
      } finally {
        initLatch.countDown();
      }
    } else if (initLatch.getCount() > 0) U.await(initLatch);

    if (sesFactory == null) throw new GridException("Cache store was not properly initialized.");
  }
  /**
   * Check how prefetch override works.
   *
   * @throws Exception IF failed.
   */
  public void testOpenPrefetchOverride() throws Exception {
    create(igfsSecondary, paths(DIR, SUBDIR), paths(FILE));

    // Write enough data to the secondary file system.
    final int blockSize = IGFS_BLOCK_SIZE;

    IgfsOutputStream out = igfsSecondary.append(FILE, false);

    int totalWritten = 0;

    while (totalWritten < blockSize * 2 + chunk.length) {
      out.write(chunk);

      totalWritten += chunk.length;
    }

    out.close();

    awaitFileClose(igfsSecondary.asSecondary(), FILE);

    // Instantiate file system with overridden "seq reads before prefetch" property.
    Configuration cfg = new Configuration();

    cfg.addResource(U.resolveIgniteUrl(PRIMARY_CFG));

    int seqReads = SEQ_READS_BEFORE_PREFETCH + 1;

    cfg.setInt(String.format(PARAM_IGFS_SEQ_READS_BEFORE_PREFETCH, "igfs:grid@"), seqReads);

    FileSystem fs = FileSystem.get(new URI(PRIMARY_URI), cfg);

    // Read the first two blocks.
    Path fsHome = new Path(PRIMARY_URI);
    Path dir = new Path(fsHome, DIR.name());
    Path subdir = new Path(dir, SUBDIR.name());
    Path file = new Path(subdir, FILE.name());

    FSDataInputStream fsIn = fs.open(file);

    final byte[] readBuf = new byte[blockSize * 2];

    fsIn.readFully(0, readBuf, 0, readBuf.length);

    // Wait for a while for prefetch to finish (if any).
    IgfsMetaManager meta = igfs.context().meta();

    IgfsFileInfo info = meta.info(meta.fileId(FILE));

    IgfsBlockKey key = new IgfsBlockKey(info.id(), info.affinityKey(), info.evictExclude(), 2);

    IgniteCache<IgfsBlockKey, byte[]> dataCache =
        igfs.context().kernalContext().cache().jcache(igfs.configuration().getDataCacheName());

    for (int i = 0; i < 10; i++) {
      if (dataCache.containsKey(key)) break;
      else U.sleep(100);
    }

    fsIn.close();

    // Remove the file from the secondary file system.
    igfsSecondary.delete(FILE, false);

    // Try reading the third block. Should fail.
    GridTestUtils.assertThrows(
        log,
        new Callable<Object>() {
          @Override
          public Object call() throws Exception {
            IgfsInputStream in0 = igfs.open(FILE);

            in0.seek(blockSize * 2);

            try {
              in0.read(readBuf);
            } finally {
              U.closeQuiet(in0);
            }

            return null;
          }
        },
        IOException.class,
        "Failed to read data due to secondary file system exception: /dir/subdir/file");
  }