/*
    * Copyright The Apache Software Foundation
    *
    * 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.
   */
  
  package org.apache.hadoop.hbase.fs;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.lang.reflect.Field;
  import java.lang.reflect.InvocationHandler;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  import java.lang.reflect.Proxy;
  import java.lang.reflect.UndeclaredThrowableException;
  import java.net.URI;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FSDataOutputStream;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.FilterFileSystem;
  import org.apache.hadoop.fs.LocalFileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.wal.DefaultWALProvider;
  import org.apache.hadoop.hdfs.DFSClient;
  import org.apache.hadoop.hdfs.DistributedFileSystem;
  import org.apache.hadoop.hdfs.protocol.ClientProtocol;
  import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
  import org.apache.hadoop.hdfs.protocol.LocatedBlock;
  import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
  import org.apache.hadoop.ipc.RPC;
  import org.apache.hadoop.util.Progressable;
  import org.apache.hadoop.util.ReflectionUtils;
  
  /**
   * An encapsulation for the FileSystem object that hbase uses to access
   * data. This class allows the flexibility of using  
   * separate filesystem objects for reading and writing hfiles and wals.
   * In future, if we want to make wals be in a different filesystem,
   * this is the place to make it happen.
   */
  public class HFileSystem extends FilterFileSystem {
    public static final Log LOG = LogFactory.getLog(HFileSystem.class);
  
    private final FileSystem noChecksumFs;   // read hfile data from storage
    private final boolean useHBaseChecksum;
  
    /**
     * Create a FileSystem object for HBase regionservers.
     * @param conf The configuration to be used for the filesystem
     * @param useHBaseChecksum if true, then use
     *        checksum verfication in hbase, otherwise
     *        delegate checksum verification to the FileSystem.
     */
    public HFileSystem(Configuration conf, boolean useHBaseChecksum)
      throws IOException {
  
      // Create the default filesystem with checksum verification switched on.
      // By default, any operation to this FilterFileSystem occurs on
      // the underlying filesystem that has checksums switched on.
      this.fs = FileSystem.get(conf);
      this.useHBaseChecksum = useHBaseChecksum;
      
      fs.initialize(getDefaultUri(conf), conf);
      
      // disable checksum verification for local fileSystem, see HBASE-11218
      if (fs instanceof LocalFileSystem) {
        fs.setWriteChecksum(false);
        fs.setVerifyChecksum(false);
      }
  
      addLocationsOrderInterceptor(conf);
  
      // If hbase checksum verification is switched on, then create a new
      // filesystem object that has cksum verification turned off.
      // We will avoid verifying checksums in the fs client, instead do it
      // inside of hbase.
      // If this is the local file system hadoop has a bug where seeks
      // do not go to the correct location if setVerifyChecksum(false) is called.
      // This manifests itself in that incorrect data is read and HFileBlocks won't be able to read
     // their header magic numbers. See HBASE-5885
     if (useHBaseChecksum && !(fs instanceof LocalFileSystem)) {
       conf = new Configuration(conf);
       conf.setBoolean("dfs.client.read.shortcircuit.skip.checksum", true);
       this.noChecksumFs = newInstanceFileSystem(conf);
       this.noChecksumFs.setVerifyChecksum(false);
     } else {
       this.noChecksumFs = fs;
     }
   }
 
   /**
    * Wrap a FileSystem object within a HFileSystem. The noChecksumFs and
    * writefs are both set to be the same specified fs. 
    * Do not verify hbase-checksums while reading data from filesystem.
    * @param fs Set the noChecksumFs and writeFs to this specified filesystem.
    */
   public HFileSystem(FileSystem fs) {
     this.fs = fs;
     this.noChecksumFs = fs;
     this.useHBaseChecksum = false;
   }
 
   /**
    * Returns the filesystem that is specially setup for 
    * doing reads from storage. This object avoids doing 
    * checksum verifications for reads.
    * @return The FileSystem object that can be used to read data
    *         from files.
    */
   public FileSystem getNoChecksumFs() {
     return noChecksumFs;
   }
 
   /**
    * Returns the underlying filesystem
    * @return The underlying FileSystem for this FilterFileSystem object.
    */
   public FileSystem getBackingFs() throws IOException {
     return fs;
   }
 
   /**
    * Are we verifying checksums in HBase?
    * @return True, if hbase is configured to verify checksums,
    *         otherwise false.
    */
   public boolean useHBaseChecksum() {
     return useHBaseChecksum;
   }
 
   /**
    * Close this filesystem object
    */
   @Override
   public void close() throws IOException {
     super.close();
     if (this.noChecksumFs != fs) {
       this.noChecksumFs.close();
     }
   }
 
  /**
    * Returns a brand new instance of the FileSystem. It does not use
    * the FileSystem.Cache. In newer versions of HDFS, we can directly
    * invoke FileSystem.newInstance(Configuration).
    * 
    * @param conf Configuration
    * @return A new instance of the filesystem
    */
   private static FileSystem newInstanceFileSystem(Configuration conf)
     throws IOException {
     URI uri = FileSystem.getDefaultUri(conf);
     FileSystem fs = null;
     Class<?> clazz = conf.getClass("fs." + uri.getScheme() + ".impl", null);
     if (clazz != null) {
       // This will be true for Hadoop 1.0, or 0.20.
       fs = (FileSystem)ReflectionUtils.newInstance(clazz, conf);
       fs.initialize(uri, conf);
     } else {
       // For Hadoop 2.0, we have to go through FileSystem for the filesystem
       // implementation to be loaded by the service loader in case it has not
       // been loaded yet.
       Configuration clone = new Configuration(conf);
       clone.setBoolean("fs." + uri.getScheme() + ".impl.disable.cache", true);
       fs = FileSystem.get(uri, clone);
     }
     if (fs == null) {
       throw new IOException("No FileSystem for scheme: " + uri.getScheme());
     }
 
     return fs;
   }
 
   public static boolean addLocationsOrderInterceptor(Configuration conf) throws IOException {
     return addLocationsOrderInterceptor(conf, new ReorderWALBlocks());
   }
 
   /**
    * Add an interceptor on the calls to the namenode#getBlockLocations from the DFSClient
    * linked to this FileSystem. See HBASE-6435 for the background.
    * <p/>
    * There should be no reason, except testing, to create a specific ReorderBlocks.
    *
    * @return true if the interceptor was added, false otherwise.
    */
   static boolean addLocationsOrderInterceptor(Configuration conf, final ReorderBlocks lrb) {
     if (!conf.getBoolean("hbase.filesystem.reorder.blocks", true)) {  // activated by default
       LOG.debug("addLocationsOrderInterceptor configured to false");
       return false;
     }
 
     FileSystem fs;
     try {
       fs = FileSystem.get(conf);
     } catch (IOException e) {
       LOG.warn("Can't get the file system from the conf.", e);
       return false;
     }
 
     if (!(fs instanceof DistributedFileSystem)) {
       LOG.debug("The file system is not a DistributedFileSystem. " +
           "Skipping on block location reordering");
       return false;
     }
 
     DistributedFileSystem dfs = (DistributedFileSystem) fs;
     DFSClient dfsc = dfs.getClient();
     if (dfsc == null) {
       LOG.warn("The DistributedFileSystem does not contain a DFSClient. Can't add the location " +
           "block reordering interceptor. Continuing, but this is unexpected."
       );
       return false;
     }
 
     try {
       Field nf = DFSClient.class.getDeclaredField("namenode");
       nf.setAccessible(true);
       Field modifiersField = Field.class.getDeclaredField("modifiers");
       modifiersField.setAccessible(true);
       modifiersField.setInt(nf, nf.getModifiers() & ~Modifier.FINAL);
 
       ClientProtocol namenode = (ClientProtocol) nf.get(dfsc);
       if (namenode == null) {
         LOG.warn("The DFSClient is not linked to a namenode. Can't add the location block" +
             " reordering interceptor. Continuing, but this is unexpected."
         );
         return false;
       }
 
       ClientProtocol cp1 = createReorderingProxy(namenode, lrb, conf);
       nf.set(dfsc, cp1);
       LOG.info("Added intercepting call to namenode#getBlockLocations so can do block reordering" +
         " using class " + lrb.getClass().getName());
     } catch (NoSuchFieldException e) {
       LOG.warn("Can't modify the DFSClient#namenode field to add the location reorder.", e);
       return false;
     } catch (IllegalAccessException e) {
       LOG.warn("Can't modify the DFSClient#namenode field to add the location reorder.", e);
       return false;
     }
 
     return true;
   }
 
   private static ClientProtocol createReorderingProxy(final ClientProtocol cp,
       final ReorderBlocks lrb, final Configuration conf) {
     return (ClientProtocol) Proxy.newProxyInstance
         (cp.getClass().getClassLoader(),
             new Class[]{ClientProtocol.class, Closeable.class},
             new InvocationHandler() {
               public Object invoke(Object proxy, Method method,
                                    Object[] args) throws Throwable {
                 try {
                   if ((args == null || args.length == 0)
                       && "close".equals(method.getName())) {
                     RPC.stopProxy(cp);
                     return null;
                   } else {
                     Object res = method.invoke(cp, args);
                     if (res != null && args != null && args.length == 3
                         && "getBlockLocations".equals(method.getName())
                         && res instanceof LocatedBlocks
                         && args[0] instanceof String
                         && args[0] != null) {
                       lrb.reorderBlocks(conf, (LocatedBlocks) res, (String) args[0]);
                     }
                     return res;
                   }
                 } catch  (InvocationTargetException ite) {
                   // We will have this for all the exception, checked on not, sent
                   //  by any layer, including the functional exception
                   Throwable cause = ite.getCause();
                   if (cause == null){
                     throw new RuntimeException(
                       "Proxy invocation failed and getCause is null", ite);
                   }
                   if (cause instanceof UndeclaredThrowableException) {
                     Throwable causeCause = cause.getCause();
                     if (causeCause == null) {
                       throw new RuntimeException("UndeclaredThrowableException had null cause!");
                     }
                     cause = cause.getCause();
                   }
                   throw cause;
                 }
               }
             });
   }
 
   /**
    * Interface to implement to add a specific reordering logic in hdfs.
    */
   interface ReorderBlocks {
     /**
      *
      * @param conf - the conf to use
      * @param lbs - the LocatedBlocks to reorder
      * @param src - the file name currently read
      * @throws IOException - if something went wrong
      */
     void reorderBlocks(Configuration conf, LocatedBlocks lbs, String src) throws IOException;
   }
 
   /**
    * We're putting at lowest priority the wal files blocks that are on the same datanode
    * as the original regionserver which created these files. This because we fear that the
    * datanode is actually dead, so if we use it it will timeout.
    */
   static class ReorderWALBlocks implements ReorderBlocks {
     public void reorderBlocks(Configuration conf, LocatedBlocks lbs, String src)
         throws IOException {
 
       ServerName sn = DefaultWALProvider.getServerNameFromWALDirectoryName(conf, src);
       if (sn == null) {
         // It's not an WAL
         return;
       }
 
       // Ok, so it's an WAL
       String hostName = sn.getHostname();
       if (LOG.isTraceEnabled()) {
         LOG.trace(src +
             " is an WAL file, so reordering blocks, last hostname will be:" + hostName);
       }
 
       // Just check for all blocks
       for (LocatedBlock lb : lbs.getLocatedBlocks()) {
         DatanodeInfo[] dnis = lb.getLocations();
         if (dnis != null && dnis.length > 1) {
           boolean found = false;
           for (int i = 0; i < dnis.length - 1 && !found; i++) {
             if (hostName.equals(dnis[i].getHostName())) {
               // advance the other locations by one and put this one at the last place.
               DatanodeInfo toLast = dnis[i];
               System.arraycopy(dnis, i + 1, dnis, i, dnis.length - i - 1);
               dnis[dnis.length - 1] = toLast;
               found = true;
             }
           }
         }
       }
     }
   }
 
   /**
    * Create a new HFileSystem object, similar to FileSystem.get().
    * This returns a filesystem object that avoids checksum
    * verification in the filesystem for hfileblock-reads.
    * For these blocks, checksum verification is done by HBase.
    */
   static public FileSystem get(Configuration conf) throws IOException {
     return new HFileSystem(conf, true);
   }
 
   /**
    * Wrap a LocalFileSystem within a HFileSystem.
    */
   static public FileSystem getLocalFs(Configuration conf) throws IOException {
     return new HFileSystem(FileSystem.getLocal(conf));
   }
 
   /**
    * The org.apache.hadoop.fs.FilterFileSystem does not yet support 
    * createNonRecursive. This is a hadoop bug and when it is fixed in Hadoop,
    * this definition will go away.
    */
   @SuppressWarnings("deprecation")
   public FSDataOutputStream createNonRecursive(Path f,
       boolean overwrite,
       int bufferSize, short replication, long blockSize,
       Progressable progress) throws IOException {
     return fs.createNonRecursive(f, overwrite, bufferSize, replication,
                                  blockSize, progress);
   }
 }