* 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,

* 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.

*/

  private static final Text EMPTY_TEXT = new Text();

 

  static class Opts extends Help {

    @Parameter(names={"-v", "--verbose"}, description="extra information will get printed to stdout also")

    boolean verbose = false;

    @Parameter(names={"-s", "--safemode"}, description="safe mode will not delete files")

    boolean safeMode = false;

    @Parameter(names={"-o", "--offline"}, description=

      "offline mode will run once and check data files directly; this is dangerous if accumulo is running or not shut down properly")

    boolean offline = false;

    @Parameter(names={"-a", "--address"}, description="specify our local address")

    String address = null;

  }

  // how much of the JVM's available memory should it use gathering candidates

  private static final float CANDIDATE_MEMORY_PERCENTAGE = 0.75f;

  private boolean candidateMemExceeded;

 

  private static final Logger log = Logger.getLogger(SimpleGarbageCollector.class);

   

  private TCredentials credentials;

  private long gcStartDelay;

  private boolean checkForBulkProcessingFiles;

  private FileSystem fs;

  private Trash trash = null;

  private boolean safemode = false, offline = false, verbose = false;

  private ZooLock lock;

  private Key continueKey = null;

 

  private GCStatus status = new GCStatus(new GcCycleStats(), new GcCycleStats(), new GcCycleStats(), new GcCycleStats());

 

  private int numDeleteThreads;

 

  private Instance instance;

 

  public static void main(String[] args) throws UnknownHostException, IOException {

    SecurityUtil.serverLogin();

   

    Instance instance = HdfsZooInstance.getInstance();

    ServerConfiguration serverConf = new ServerConfiguration(instance);

    final FileSystem fs = FileUtil.getFileSystem(CachedConfiguration.getInstance(), serverConf.getConfiguration());

    Accumulo.init(fs, serverConf, "gc");

    String address = "localhost";

    SimpleGarbageCollector gc = new SimpleGarbageCollector();

    Opts opts = new Opts();

    opts.parseArgs(SimpleGarbageCollector.class.getName(), args);

   

    if (opts.safeMode)

      gc.setSafeMode();

    if (opts.offline)

      gc.setOffline();

    if (opts.verbose)

      gc.setVerbose();

    if (opts.address != null)

      address = opts.address;

    String hostname = address;

    // Catch a few edge cases where we might get a non-useful address

    if ("0.0.0.0".equals(address)) {

      // Get a better hostname for this system

      hostname = InetAddress.getLocalHost().getHostName();

    }

   

    gc.init(fs, instance, SecurityConstants.getSystemCredentials(), serverConf.getConfiguration().getBoolean(Property.GC_TRASH_IGNORE));

    Accumulo.enableTracing(hostname, "gc");

    gc.run(hostname);

  }

 

  public SimpleGarbageCollector() {}

 

  public void setSafeMode() {

    this.safemode = true;

  }

 

  public void setOffline() {

    this.offline = true;

  }

 

  public void setVerbose() {

    this.verbose = true;

  }

 

  public void init(FileSystem fs, Instance instance, TCredentials credentials, boolean noTrash) throws IOException {

    this.fs = TraceFileSystem.wrap(fs);

    this.credentials = credentials;

    this.instance = instance;

   

    gcStartDelay = instance.getConfiguration().getTimeInMillis(Property.GC_CYCLE_START);

    long gcDelay = instance.getConfiguration().getTimeInMillis(Property.GC_CYCLE_DELAY);

    numDeleteThreads = instance.getConfiguration().getCount(Property.GC_DELETE_THREADS);

    log.info("start delay: " + (offline ? 0 + " sec (offline)" : gcStartDelay + " milliseconds"));

    log.info("time delay: " + gcDelay + " milliseconds");

    log.info("safemode: " + safemode);

    log.info("offline: " + offline);

    log.info("verbose: " + verbose);

    log.info("memory threshold: " + CANDIDATE_MEMORY_PERCENTAGE + " of " + Runtime.getRuntime().maxMemory() + " bytes");

    log.info("delete threads: " + numDeleteThreads);

    if (!noTrash) {

      this.trash = new Trash(fs, fs.getConf());

    }

  }

 

  private void run(String hostname) {

    long tStart, tStop;

   

    // Sleep for an initial period, giving the master time to start up and

    // old data files to be unused

    if (!offline) {

      try {

        getZooLock(startStatsService(hostname));

      } catch (Exception ex) {

        log.error(ex, ex);

        System.exit(1);

      }

     

      try {

        log.debug("Sleeping for " + gcStartDelay + " milliseconds before beginning garbage collection cycles");

        Thread.sleep(gcStartDelay);

      } catch (InterruptedException e) {

        log.warn(e, e);

        return;

      }

    }

   

    Sampler sampler = new CountSampler(100);

   

    while (true) {

      if (sampler.next())

        Trace.on("gc");

     

      Span gcSpan = Trace.start("loop");

      tStart = System.currentTimeMillis();

      try {

        // STEP 1: gather candidates

        System.gc(); // make room

        candidateMemExceeded = false;

        checkForBulkProcessingFiles = false;

       

        Span candidatesSpan = Trace.start("getCandidates");

        status.current.started = System.currentTimeMillis();

        SortedSet<String> candidates = getCandidates();

        status.current.candidates = candidates.size();

        candidatesSpan.stop();

       

        // STEP 2: confirm deletes

        // WARNING: This line is EXTREMELY IMPORTANT.

        // You MUST confirm candidates are okay to delete

        Span confirmDeletesSpan = Trace.start("confirmDeletes");

        confirmDeletes(candidates);

        status.current.inUse = status.current.candidates - candidates.size();

        confirmDeletesSpan.stop();

       

        // STEP 3: delete files

        if (safemode) {

          if (verbose)

            System.out.println("SAFEMODE: There are " + candidates.size() + " data file candidates marked for deletion.%n"

                + "          Examine the log files to identify them.%n" + "          They can be removed by executing: bin/accumulo gc --offline%n"

                + "WARNING:  Do not run the garbage collector in offline mode unless you are positive%n"

                + "          that the accumulo METADATA table is in a clean state, or that accumulo%n"

                + "          has not yet been run, in the case of an upgrade.");

          log.info("SAFEMODE: Listing all data file candidates for deletion");

          for (String s : candidates)

            log.info("SAFEMODE: " + s);

          log.info("SAFEMODE: End candidates for deletion");

        } else {

          Span deleteSpan = Trace.start("deleteFiles");

          deleteFiles(candidates);

          log.info("Number of data file candidates for deletion: " + status.current.candidates);

          log.info("Number of data file candidates still in use: " + status.current.inUse);

          log.info("Number of successfully deleted data files: " + status.current.deleted);

          log.info("Number of data files delete failures: " + status.current.errors);

          deleteSpan.stop();

         

          // delete empty dirs of deleted tables

          // this can occur as a result of cloning

          cleanUpDeletedTableDirs(candidates);

        }

       

        status.current.finished = System.currentTimeMillis();

        status.last = status.current;

        status.current = new GcCycleStats();

       

      } catch (Exception e) {

        log.error(e, e);

      }

      tStop = System.currentTimeMillis();

      log.info(String.format("Collect cycle took %.2f seconds", ((tStop - tStart) / 1000.0)));

     

      if (offline)

        break;

     

      if (candidateMemExceeded) {

        log.info("Gathering of candidates was interrupted due to memory shortage. Bypassing cycle delay to collect the remaining candidates.");

        continue;

      }

     

      // Clean up any unused write-ahead logs

      Span waLogs = Trace.start("walogs");

      try {

        GarbageCollectWriteAheadLogs walogCollector = new GarbageCollectWriteAheadLogs(instance, fs, trash == null);

        log.info("Beginning garbage collection of write-ahead logs");

        walogCollector.collect(status);

      } catch (Exception e) {

        log.error(e, e);

      }

      waLogs.stop();

      gcSpan.stop();

     

      // we just made a lot of changes to the !METADATA table: flush them out

      try {

        Connector connector = instance.getConnector(credentials.getPrincipal(), CredentialHelper.extractToken(credentials));

        connector.tableOperations().compact(Constants.METADATA_TABLE_NAME, null, null, true, true);

      } catch (Exception e) {

        log.warn(e, e);

      }

     

      Trace.offNoFlush();

      try {

        long gcDelay = instance.getConfiguration().getTimeInMillis(Property.GC_CYCLE_DELAY);

        log.debug("Sleeping for " + gcDelay + " milliseconds");

        Thread.sleep(gcDelay);

      } catch (InterruptedException e) {

        log.warn(e, e);

        return;

      }

    }

  }

 

  private boolean moveToTrash(Path path) throws IOException {

    if (trash == null)

      return false;

    try {

      return trash.moveToTrash(path);

    } catch (FileNotFoundException ex) {

      return false;

    }

  }

 

  /*

   * this method removes deleted table dirs that are empty

   */

  private void cleanUpDeletedTableDirs(SortedSet<String> candidates) throws Exception {

   

    HashSet<String> tableIdsWithDeletes = new HashSet<String>();

   

    // find the table ids that had dirs deleted

    for (String delete : candidates) {

      if (isDir(delete)) {

        String tableId = delete.split("/")[1];

        tableIdsWithDeletes.add(tableId);

      }

    }

   

    Tables.clearCache(instance);

    Set<String> tableIdsInZookeeper = Tables.getIdToNameMap(instance).keySet();

   

    tableIdsWithDeletes.removeAll(tableIdsInZookeeper);

   

    // tableIdsWithDeletes should now contain the set of deleted tables that had dirs deleted

   

    for (String delTableId : tableIdsWithDeletes) {

      // if dir exist and is empty, then empty list is returned...

      // hadoop 1.0 will return null if the file doesn't exist

      // hadoop 2.0 will throw an exception if the file does not exist

      FileStatus[] tabletDirs = null;

      try {

        tabletDirs = fs.listStatus(new Path(ServerConstants.getTablesDir() + "/" + delTableId));

      } catch (FileNotFoundException ex) {

        // ignored

      }

     

      if (tabletDirs == null)

        continue;

     

      if (tabletDirs.length == 0) {

        Path p = new Path(ServerConstants.getTablesDir() + "/" + delTableId);

        if (!moveToTrash(p))

          fs.delete(p, false);

      }

    }

  }

 

  private void getZooLock(InetSocketAddress addr) throws KeeperException, InterruptedException {

    String address = AddressUtil.toString(addr);

    String path = ZooUtil.getRoot(HdfsZooInstance.getInstance()) + Constants.ZGC_LOCK;

   

    LockWatcher lockWatcher = new LockWatcher() {

      public void lostLock(LockLossReason reason) {

        Halt.halt("GC lock in zookeeper lost (reason = " + reason + "), exiting!");

      }

     

      @Override

      public void unableToMonitorLockNode(final Throwable e) {

        Halt.halt(-1, new Runnable() {

         

          @Override

          public void run() {

            log.fatal("No longer able to monitor lock node ", e);

          }

        });

       

      }

    };

   

    while (true) {

      lock = new ZooLock(path);

      if (lock.tryLock(lockWatcher, new ServerServices(address, Service.GC_CLIENT).toString().getBytes(Constants.UTF8))) {

        break;

      }

      UtilWaitThread.sleep(1000);

    }

  }

 

  private InetSocketAddress startStatsService(String hostname) throws UnknownHostException {

    Processor<Iface> processor = new Processor<Iface>(TraceWrap.service(this));

    int port = instance.getConfiguration().getPort(Property.GC_PORT);

    long maxMessageSize = instance.getConfiguration().getMemoryInBytes(Property.GENERAL_MAX_MESSAGE_SIZE);

    try {

      port = TServerUtils.startTServer(port, processor, this.getClass().getSimpleName(), "GC Monitor Service", 2, 1000, maxMessageSize).port;

    } catch (Exception ex) {

      log.fatal(ex, ex);

      throw new RuntimeException(ex);

    }

    return new InetSocketAddress(hostname, port);

  }

 

  /**

   * This method gets a set of candidates for deletion by scanning the METADATA table deleted flag keyspace

   */

  SortedSet<String> getCandidates() throws Exception {

    TreeSet<String> candidates = new TreeSet<String>();

   

    if (offline) {

      checkForBulkProcessingFiles = true;

      try {

        for (String validExtension : FileOperations.getValidExtensions()) {

          for (FileStatus stat : fs.globStatus(new Path(ServerConstants.getTablesDir() + "/*/*/*." + validExtension))) {

            String cand = stat.getPath().toUri().getPath();

            if (!cand.contains(ServerConstants.getRootTabletDir())) {

              candidates.add(cand.substring(ServerConstants.getTablesDir().length()));

              log.debug("Offline candidate: " + cand);

            }

          }

        }

      } catch (IOException e) {

        log.error("Unable to check the filesystem for offline candidates. Removing all candidates for deletion to be safe.", e);

        candidates.clear();

      }

      return candidates;

    }

    checkForBulkProcessingFiles = false;

    Range range = Constants.METADATA_DELETES_FOR_METADATA_KEYSPACE;

    candidates.addAll(getBatch(Constants.METADATA_DELETE_FLAG_FOR_METADATA_PREFIX, range));

    if (candidateMemExceeded)

      return candidates;

   

    range = Constants.METADATA_DELETES_KEYSPACE;

    candidates.addAll(getBatch(Constants.METADATA_DELETE_FLAG_PREFIX, range));

    return candidates;

  }

  private Collection<String> getBatch(String prefix, Range range) throws Exception {

    // want to ensure GC makes progress... if the 1st N deletes are stable and we keep processing them,

    // then will never inspect deletes after N

    if (continueKey != null) {

      if (!range.contains(continueKey)) {

        // continue key is for some other range

        return Collections.emptyList();

      }

      range = new Range(continueKey, true, range.getEndKey(), range.isEndKeyInclusive());

      continueKey = null;

    }

   

    Scanner scanner = instance.getConnector(credentials.getPrincipal(), CredentialHelper.extractToken(credentials)).createScanner(Constants.METADATA_TABLE_NAME, Constants.NO_AUTHS);

    scanner.setRange(range);

    List<String> result = new ArrayList<String>();

    // find candidates for deletion; chop off the prefix

    for (Entry<Key,Value> entry : scanner) {

      String cand = entry.getKey().getRow().toString().substring(prefix.length());

      result.add(cand);

      checkForBulkProcessingFiles |= cand.toLowerCase(Locale.ENGLISH).contains(Constants.BULK_PREFIX);

      if (almostOutOfMemory()) {

        candidateMemExceeded = true;

        log.info("List of delete candidates has exceeded the memory threshold. Attempting to delete what has been gathered so far.");

        continueKey = entry.getKey();

        break;

      }

    }

   

    return result;

  }

 

  static public boolean almostOutOfMemory() {

    Runtime runtime = Runtime.getRuntime();

    return runtime.totalMemory() - runtime.freeMemory() > CANDIDATE_MEMORY_PERCENTAGE * runtime.maxMemory();

  }

 

  /**

   * This method removes candidates from the candidate list under two conditions: 1. They are in the same folder as a bulk processing file, if that option is

   * selected 2. They are still in use in the file column family in the METADATA table

   */

  public void confirmDeletes(SortedSet<String> candidates) throws AccumuloException {

   

    Scanner scanner;

    if (offline) {

      try {

        scanner = new OfflineMetadataScanner(instance.getConfiguration(), fs);

      } catch (IOException e) {

        throw new IllegalStateException("Unable to create offline metadata scanner", e);

      }

    } else {

      try {

        scanner = new IsolatedScanner(instance.getConnector(credentials.getPrincipal(), CredentialHelper.extractToken(credentials)).createScanner(Constants.METADATA_TABLE_NAME, Constants.NO_AUTHS));

      } catch (AccumuloSecurityException ex) {

        throw new AccumuloException(ex);

      } catch (TableNotFoundException ex) {

        throw new AccumuloException(ex);

      }

    }

   

    // skip candidates that are in a bulk processing folder

    if (checkForBulkProcessingFiles) {

     

      log.debug("Checking for bulk processing flags");

     

      scanner.setRange(Constants.METADATA_BLIP_KEYSPACE);

     

      // WARNING: This block is IMPORTANT

      // You MUST REMOVE candidates that are in the same folder as a bulk

      // processing flag!

     

      for (Entry<Key,Value> entry : scanner) {

        String blipPath = entry.getKey().getRow().toString().substring(Constants.METADATA_BLIP_FLAG_PREFIX.length());

        Iterator<String> tailIter = candidates.tailSet(blipPath).iterator();

        int count = 0;

        while (tailIter.hasNext()) {

          if (tailIter.next().startsWith(blipPath)) {

            count++;

            tailIter.remove();

          } else {

            break;

          }

        }

       

        if (count > 0)

          log.debug("Folder has bulk processing flag: " + blipPath);

       

      }

    }

   

    // skip candidates that are still in use in the file column family in

    // the metadata table

    scanner.clearColumns();

    scanner.fetchColumnFamily(Constants.METADATA_DATAFILE_COLUMN_FAMILY);

    scanner.fetchColumnFamily(Constants.METADATA_SCANFILE_COLUMN_FAMILY);

    Constants.METADATA_DIRECTORY_COLUMN.fetch(scanner);

   

    TabletIterator tabletIterator = new TabletIterator(scanner, Constants.METADATA_KEYSPACE, false, true);

   

    while (tabletIterator.hasNext()) {

      Map<Key,Value> tabletKeyValues = tabletIterator.next();

     

      for (Entry<Key,Value> entry : tabletKeyValues.entrySet()) {

        if (entry.getKey().getColumnFamily().equals(Constants.METADATA_DATAFILE_COLUMN_FAMILY)

            || entry.getKey().getColumnFamily().equals(Constants.METADATA_SCANFILE_COLUMN_FAMILY)) {

         

          String cf = entry.getKey().getColumnQualifier().toString();

          String delete;

          if (cf.startsWith("../")) {

            delete = cf.substring(2);

          } else {

            String table = new String(KeyExtent.tableOfMetadataRow(entry.getKey().getRow()), Constants.UTF8);

            delete = "/" + table + cf;

          }

          // WARNING: This line is EXTREMELY IMPORTANT.

          // You MUST REMOVE candidates that are still in use

          if (candidates.remove(delete))

            log.debug("Candidate was still in use in the METADATA table: " + delete);

         

          String path = delete.substring(0, delete.lastIndexOf('/'));

          if (candidates.remove(path))

            log.debug("Candidate was still in use in the METADATA table: " + path);

        } else if (Constants.METADATA_DIRECTORY_COLUMN.hasColumns(entry.getKey())) {

          String table = new String(KeyExtent.tableOfMetadataRow(entry.getKey().getRow()), Constants.UTF8);

          String delete = "/" + table + entry.getValue().toString();

          if (candidates.remove(delete))

            log.debug("Candidate was still in use in the METADATA table: " + delete);

        } else

          throw new AccumuloException("Scanner over metadata table returned unexpected column : " + entry.getKey());

      }

    }

  }

  final static String METADATA_TABLE_DIR = "/" + Constants.METADATA_TABLE_ID;

  private static void putMarkerDeleteMutation(final String delete, final BatchWriter writer, final BatchWriter rootWriter) throws MutationsRejectedException {

    if (delete.startsWith(METADATA_TABLE_DIR)) {

      Mutation m = new Mutation(new Text(Constants.METADATA_DELETE_FLAG_FOR_METADATA_PREFIX + delete));

      m.putDelete(EMPTY_TEXT, EMPTY_TEXT);

      rootWriter.addMutation(m);

    } else {

      Mutation m = new Mutation(new Text(Constants.METADATA_DELETE_FLAG_PREFIX + delete));

      m.putDelete(EMPTY_TEXT, EMPTY_TEXT);

      writer.addMutation(m);

    }

  }

  /**

   * This method attempts to do its best to remove files from the filesystem that have been confirmed for deletion.

   */

  private void deleteFiles(SortedSet<String> confirmedDeletes) {

    // create a batchwriter to remove the delete flags for successful

    // deletes; Need separate writer for the root tablet.

    BatchWriter writer = null;

    BatchWriter rootWriter = null;

    if (!offline) {

      Connector c;

      try {

        c = instance.getConnector(SecurityConstants.SYSTEM_PRINCIPAL, SecurityConstants.getSystemToken());

        writer = c.createBatchWriter(Constants.METADATA_TABLE_NAME, new BatchWriterConfig());

        rootWriter = c.createBatchWriter(Constants.METADATA_TABLE_NAME, new BatchWriterConfig());

      } catch (Exception e) {

        log.error("Unable to create writer to remove file from the !METADATA table", e);

      }

    }

    // when deleting a dir and all files in that dir, only need to delete the dir

    // the dir will sort right before the files... so remove the files in this case

    // to minimize namenode ops

    Iterator<String> cdIter = confirmedDeletes.iterator();

    String lastDir = null;

    while (cdIter.hasNext()) {

      String delete = cdIter.next();

      if (isDir(delete)) {

        lastDir = delete;

      } else if (lastDir != null) {

        if (delete.startsWith(lastDir)) {

          log.debug("Ignoring " + delete + " because " + lastDir + " exist");

          try {

            putMarkerDeleteMutation(delete, writer, rootWriter);

          } catch (MutationsRejectedException e) {

            throw new RuntimeException(e);

          }

          cdIter.remove();

        } else {

          lastDir = null;

        }

       

      }

    }

   

    final BatchWriter finalWriter = writer;

    final BatchWriter finalRootWriter = rootWriter;

   

    ExecutorService deleteThreadPool = Executors.newFixedThreadPool(numDeleteThreads, new NamingThreadFactory("deleting"));

   

    for (final String delete : confirmedDeletes) {

     

      Runnable deleteTask = new Runnable() {

        @Override

        public void run() {

          boolean removeFlag;

         

          String fullPath = ServerConstants.getTablesDir() + delete;

          log.debug("Deleting " + fullPath);

          try {

           

            Path p = new Path(fullPath);

           

            if (moveToTrash(p) || fs.delete(p, true)) {

              // delete succeeded, still want to delete

              removeFlag = true;

              synchronized (SimpleGarbageCollector.this) {

                ++status.current.deleted;

              }

            } else if (fs.exists(p)) {

              // leave the entry in the METADATA table; we'll try again

              // later

              removeFlag = false;

              synchronized (SimpleGarbageCollector.this) {

                ++status.current.errors;

              }

              log.warn("File exists, but was not deleted for an unknown reason: " + p);

            } else {

              // this failure, we still want to remove the METADATA table

              // entry

              removeFlag = true;

              synchronized (SimpleGarbageCollector.this) {

                ++status.current.errors;

              }

              String parts[] = delete.split("/");

              if (parts.length > 2) {

                String tableId = parts[1];

                String tabletDir = parts[2];

                TableManager.getInstance().updateTableStateCache(tableId);

                TableState tableState = TableManager.getInstance().getTableState(tableId);

                if (tableState != null && tableState != TableState.DELETING) {

                  // clone directories don't always exist

                  if (!tabletDir.startsWith("c-"))

                    log.warn("File doesn't exist: " + p);

                }

              } else {

                log.warn("Very strange path name: " + delete);

              }

            }

           

            // proceed to clearing out the flags for successful deletes and

            // non-existent files

            if (removeFlag && finalWriter != null) {

              putMarkerDeleteMutation(delete, finalWriter, finalRootWriter);

            }

          } catch (Exception e) {

            log.error(e, e);

          }

         

        }

      };

     

      deleteThreadPool.execute(deleteTask);

    }

   

    deleteThreadPool.shutdown();

   

    try {

      while (!deleteThreadPool.awaitTermination(1000, TimeUnit.MILLISECONDS)) {}

    } catch (InterruptedException e1) {

      log.error(e1, e1);

    }

   

    if (writer != null) {

      try {

        writer.close();

      } catch (MutationsRejectedException e) {

        log.error("Problem removing entries from the metadata table: ", e);

      }

    }

    if (rootWriter != null) {

      try {

        rootWriter.close();

      } catch (MutationsRejectedException e) {

        log.error("Problem removing entries from the metadata table: ", e);

      }

    }

  }

 

  private boolean isDir(String delete) {

    int slashCount = 0;

    for (int i = 0; i < delete.length(); i++)

      if (delete.charAt(i) == '/')

        slashCount++;

    return slashCount == 2;

  }

 

  @Override

  public GCStatus getStatus(TInfo info, TCredentials credentials) {

    return status;

  }

}