/**
    *
    * 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.wal;
  
  import java.io.IOException;
  import java.util.Arrays;
  import java.io.InterruptedIOException;
  import java.util.Collections;
  import java.util.List;
  import java.util.concurrent.atomic.AtomicReference;
  
  import com.google.common.annotations.VisibleForTesting;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FSDataInputStream;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.wal.WAL.Reader;
  import org.apache.hadoop.hbase.wal.WALProvider.Writer;
  import org.apache.hadoop.hbase.util.CancelableProgressable;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  
  // imports for things that haven't moved from regionserver.wal yet.
  import org.apache.hadoop.hbase.regionserver.wal.MetricsWAL;
  import org.apache.hadoop.hbase.regionserver.wal.ProtobufLogReader;
  import org.apache.hadoop.hbase.regionserver.wal.SequenceFileLogReader;
  import org.apache.hadoop.hbase.regionserver.wal.WALActionsListener;
  
  /**
   * Entry point for users of the Write Ahead Log.
   * Acts as the shim between internal use and the particular WALProvider we use to handle wal
   * requests.
   *
   * Configure which provider gets used with the configuration setting "hbase.wal.provider". Available
   * implementations:
   * <ul>
   *   <li><em>defaultProvider</em> : whatever provider is standard for the hbase version. Currently
   *                                  "filesystem"</li>
   *   <li><em>filesystem</em> : a provider that will run on top of an implementation of the Hadoop
   *                             FileSystem interface, normally HDFS.</li>
   *   <li><em>multiwal</em> : a provider that will use multiple "filesystem" wal instances per region
   *                           server.</li>
   * </ul>
   *
   * Alternatively, you may provide a custom implementation of {@link WALProvider} by class name.
   */
  @InterfaceAudience.Private
  public class WALFactory {
  
    private static final Log LOG = LogFactory.getLog(WALFactory.class);
  
    /**
     * Maps between configuration names for providers and implementation classes.
     */
    static enum Providers {
      defaultProvider(DefaultWALProvider.class),
      filesystem(DefaultWALProvider.class),
      multiwal(RegionGroupingProvider.class);
  
      Class<? extends WALProvider> clazz;
      Providers(Class<? extends WALProvider> clazz) {
        this.clazz = clazz;
      }
    }
  
    public static final String WAL_PROVIDER = "hbase.wal.provider";
    static final String DEFAULT_WAL_PROVIDER = Providers.defaultProvider.name();
  
    static final String META_WAL_PROVIDER = "hbase.wal.meta_provider";
    static final String DEFAULT_META_WAL_PROVIDER = Providers.defaultProvider.name();
  
    final String factoryId;
    final WALProvider provider;
    // The meta updates are written to a different wal. If this
    // regionserver holds meta regions, then this ref will be non-null.
    // lazily intialized; most RegionServers don't deal with META
    final AtomicReference<WALProvider> metaProvider = new AtomicReference<WALProvider>();
  
    /**
    * Configuration-specified WAL Reader used when a custom reader is requested
    */
   private final Class<? extends DefaultWALProvider.Reader> logReaderClass;
 
   /**
    * How long to attempt opening in-recovery wals
    */
   private final int timeoutMillis;
 
   private final Configuration conf;
 
   // Used for the singleton WALFactory, see below.
   private WALFactory(Configuration conf) {
     // this code is duplicated here so we can keep our members final.
     // until we've moved reader/writer construction down into providers, this initialization must
     // happen prior to provider initialization, in case they need to instantiate a reader/writer.
     timeoutMillis = conf.getInt("hbase.hlog.open.timeout", 300000);
     /* TODO Both of these are probably specific to the fs wal provider */
     logReaderClass = conf.getClass("hbase.regionserver.hlog.reader.impl", ProtobufLogReader.class,
         DefaultWALProvider.Reader.class);
     this.conf = conf;
     // end required early initialization
 
     // this instance can't create wals, just reader/writers.
     provider = null;
     factoryId = SINGLETON_ID;
   }
 
   /**
    * instantiate a provider from a config property.
    * requires conf to have already been set (as well as anything the provider might need to read).
    */
   WALProvider getProvider(final String key, final String defaultValue,
       final List<WALActionsListener> listeners, final String providerId) throws IOException {
     Class<? extends WALProvider> clazz;
     try {
       clazz = Providers.valueOf(conf.get(key, defaultValue)).clazz;
     } catch (IllegalArgumentException exception) {
       // Fall back to them specifying a class name
       // Note that the passed default class shouldn't actually be used, since the above only fails
       // when there is a config value present.
       clazz = conf.getClass(key, DefaultWALProvider.class, WALProvider.class);
     }
     LOG.info("Instantiating WALProvider of type " + clazz);
     try {
       final WALProvider result = clazz.newInstance();
       result.init(this, conf, listeners, providerId);
       return result;
     } catch (InstantiationException exception) {
       LOG.error("couldn't set up WALProvider, check config key " + key);
       LOG.debug("Exception details for failure to load WALProvider.", exception);
       throw new IOException("couldn't set up WALProvider", exception);
     } catch (IllegalAccessException exception) {
       LOG.error("couldn't set up WALProvider, check config key " + key);
       LOG.debug("Exception details for failure to load WALProvider.", exception);
       throw new IOException("couldn't set up WALProvider", exception);
     }
   }
 
   /**
    * @param conf must not be null, will keep a reference to read params in later reader/writer
    *     instances.
    * @param listeners may be null. will be given to all created wals (and not meta-wals)
    * @param factoryId a unique identifier for this factory. used i.e. by filesystem implementations
    *     to make a directory
    */
   public WALFactory(final Configuration conf, final List<WALActionsListener> listeners,
       final String factoryId) throws IOException {
     // until we've moved reader/writer construction down into providers, this initialization must
     // happen prior to provider initialization, in case they need to instantiate a reader/writer.
     timeoutMillis = conf.getInt("hbase.hlog.open.timeout", 300000);
     /* TODO Both of these are probably specific to the fs wal provider */
     logReaderClass = conf.getClass("hbase.regionserver.hlog.reader.impl", ProtobufLogReader.class,
         DefaultWALProvider.Reader.class);
     this.conf = conf;
     this.factoryId = factoryId;
     // end required early initialization
     if (conf.getBoolean("hbase.regionserver.hlog.enabled", true)) {
       provider = getProvider(WAL_PROVIDER, DEFAULT_WAL_PROVIDER, listeners, null);
     } else {
       // special handling of existing configuration behavior.
       LOG.warn("Running with WAL disabled.");
       provider = new DisabledWALProvider();
       provider.init(this, conf, null, factoryId);
     }
   }
 
   /**
    * Shutdown all WALs and clean up any underlying storage.
    * Use only when you will not need to replay and edits that have gone to any wals from this
    * factory.
    */
   public void close() throws IOException {
     final WALProvider metaProvider = this.metaProvider.get();
     if (null != metaProvider) {
       metaProvider.close();
     }
     // close is called on a WALFactory with null provider in the case of contention handling
     // within the getInstance method.
     if (null != provider) {
       provider.close();
     }
   }
 
   /**
    * Tell the underlying WAL providers to shut down, but do not clean up underlying storage.
    * If you are not ending cleanly and will need to replay edits from this factory's wals,
    * use this method if you can as it will try to leave things as tidy as possible.
    */
   public void shutdown() throws IOException {
     IOException exception = null;
     final WALProvider metaProvider = this.metaProvider.get();
     if (null != metaProvider) {
       try {
         metaProvider.shutdown();
       } catch(IOException ioe) {
         exception = ioe;
       }
     }
     provider.shutdown();
     if (null != exception) {
       throw exception;
     }
   }
 
   /**
    * @param identifier may not be null, contents will not be altered
    * @param namespace could be null, and will use default namespace if null
    */
   public WAL getWAL(final byte[] identifier, final byte[] namespace) throws IOException {
     return provider.getWAL(identifier, namespace);
   }
 
   /**
    * @param identifier may not be null, contents will not be altered
    */
   public WAL getMetaWAL(final byte[] identifier) throws IOException {
     WALProvider metaProvider = this.metaProvider.get();
     if (null == metaProvider) {
       final WALProvider temp = getProvider(META_WAL_PROVIDER, DEFAULT_META_WAL_PROVIDER,
           Collections.<WALActionsListener>singletonList(new MetricsWAL()),
           DefaultWALProvider.META_WAL_PROVIDER_ID);
       if (this.metaProvider.compareAndSet(null, temp)) {
         metaProvider = temp;
       } else {
         // reference must now be to a provider created in another thread.
         temp.close();
         metaProvider = this.metaProvider.get();
       }
     }
     return metaProvider.getWAL(identifier, null);
   }
 
   public Reader createReader(final FileSystem fs, final Path path) throws IOException {
     return createReader(fs, path, (CancelableProgressable)null);
   }
 
   /**
    * Create a reader for the WAL. If you are reading from a file that's being written to and need
    * to reopen it multiple times, use {@link WAL.Reader#reset()} instead of this method
    * then just seek back to the last known good position.
    * @return A WAL reader.  Close when done with it.
    * @throws IOException
    */
   public Reader createReader(final FileSystem fs, final Path path,
       CancelableProgressable reporter) throws IOException {
     return createReader(fs, path, reporter, true);
   }
 
   public Reader createReader(final FileSystem fs, final Path path,
       CancelableProgressable reporter, boolean allowCustom)
       throws IOException {
     Class<? extends DefaultWALProvider.Reader> lrClass =
         allowCustom ? logReaderClass : ProtobufLogReader.class;
 
     try {
       // A wal file could be under recovery, so it may take several
       // tries to get it open. Instead of claiming it is corrupted, retry
       // to open it up to 5 minutes by default.
       long startWaiting = EnvironmentEdgeManager.currentTime();
       long openTimeout = timeoutMillis + startWaiting;
       int nbAttempt = 0;
       FSDataInputStream stream = null;
       while (true) {
         try {
           if (lrClass != ProtobufLogReader.class) {
             // User is overriding the WAL reader, let them.
             DefaultWALProvider.Reader reader = lrClass.newInstance();
             reader.init(fs, path, conf, null);
             return reader;
           } else {
             stream = fs.open(path);
             // Note that zero-length file will fail to read PB magic, and attempt to create
             // a non-PB reader and fail the same way existing code expects it to. If we get
             // rid of the old reader entirely, we need to handle 0-size files differently from
             // merely non-PB files.
             byte[] magic = new byte[ProtobufLogReader.PB_WAL_MAGIC.length];
             boolean isPbWal = (stream.read(magic) == magic.length)
                 && Arrays.equals(magic, ProtobufLogReader.PB_WAL_MAGIC);
             DefaultWALProvider.Reader reader =
                 isPbWal ? new ProtobufLogReader() : new SequenceFileLogReader();
             reader.init(fs, path, conf, stream);
             return reader;
           }
         } catch (IOException e) {
           try {
             if (stream != null) {
               stream.close();
             }
           } catch (IOException exception) {
             LOG.warn("Could not close FSDataInputStream" + exception.getMessage());
             LOG.debug("exception details", exception);
           }
           String msg = e.getMessage();
           if (msg != null && (msg.contains("Cannot obtain block length")
               || msg.contains("Could not obtain the last block")
               || msg.matches("Blocklist for [^ ]* has changed.*"))) {
             if (++nbAttempt == 1) {
               LOG.warn("Lease should have recovered. This is not expected. Will retry", e);
             }
             if (reporter != null && !reporter.progress()) {
               throw new InterruptedIOException("Operation is cancelled");
             }
             if (nbAttempt > 2 && openTimeout < EnvironmentEdgeManager.currentTime()) {
               LOG.error("Can't open after " + nbAttempt + " attempts and "
                 + (EnvironmentEdgeManager.currentTime() - startWaiting)
                 + "ms " + " for " + path);
             } else {
               try {
                 Thread.sleep(nbAttempt < 3 ? 500 : 1000);
                 continue; // retry
               } catch (InterruptedException ie) {
                 InterruptedIOException iioe = new InterruptedIOException();
                 iioe.initCause(ie);
                 throw iioe;
               }
             }
           }
           throw e;
         }
       }
     } catch (IOException ie) {
       throw ie;
     } catch (Exception e) {
       throw new IOException("Cannot get log reader", e);
     }
   }
 
   /**
    * Create a writer for the WAL.
    * should be package-private. public only for tests and
    * {@link org.apache.hadoop.hbase.regionserver.wal.Compressor}
    * @return A WAL writer.  Close when done with it.
    * @throws IOException
    */
   public Writer createWALWriter(final FileSystem fs, final Path path) throws IOException {
     return DefaultWALProvider.createWriter(conf, fs, path, false);
   }
 
   /**
    * should be package-private, visible for recovery testing.
    * @return an overwritable writer for recovered edits. caller should close.
    */
   @VisibleForTesting
   public Writer createRecoveredEditsWriter(final FileSystem fs, final Path path)
       throws IOException {
     return DefaultWALProvider.createWriter(conf, fs, path, true);
   }
 
   // These static methods are currently used where it's impractical to
   // untangle the reliance on state in the filesystem. They rely on singleton
   // WALFactory that just provides Reader / Writers.
   // For now, first Configuration object wins. Practically this just impacts the reader/writer class
   private static final AtomicReference<WALFactory> singleton = new AtomicReference<WALFactory>();
   private static final String SINGLETON_ID = WALFactory.class.getName();
   
   // public only for FSHLog
   public static WALFactory getInstance(Configuration configuration) {
     WALFactory factory = singleton.get();
     if (null == factory) {
       WALFactory temp = new WALFactory(configuration);
       if (singleton.compareAndSet(null, temp)) {
         factory = temp;
       } else {
         // someone else beat us to initializing
         try {
           temp.close();
         } catch (IOException exception) {
           LOG.debug("failed to close temporary singleton. ignoring.", exception);
         }
         factory = singleton.get();
       }
     }
     return factory;
   }
 
   /**
    * Create a reader for the given path, accept custom reader classes from conf.
    * If you already have a WALFactory, you should favor the instance method.
    * @return a WAL Reader, caller must close.
    */
   public static Reader createReader(final FileSystem fs, final Path path,
       final Configuration configuration) throws IOException {
     return getInstance(configuration).createReader(fs, path);
   }
 
   /**
    * Create a reader for the given path, accept custom reader classes from conf.
    * If you already have a WALFactory, you should favor the instance method.
    * @return a WAL Reader, caller must close.
    */
   static Reader createReader(final FileSystem fs, final Path path,
       final Configuration configuration, final CancelableProgressable reporter) throws IOException {
     return getInstance(configuration).createReader(fs, path, reporter);
   }
 
   /**
    * Create a reader for the given path, ignore custom reader classes from conf.
    * If you already have a WALFactory, you should favor the instance method.
    * only public pending move of {@link org.apache.hadoop.hbase.regionserver.wal.Compressor}
    * @return a WAL Reader, caller must close.
    */
   public static Reader createReaderIgnoreCustomClass(final FileSystem fs, final Path path,
       final Configuration configuration) throws IOException {
     return getInstance(configuration).createReader(fs, path, null, false);
   }
 
   /**
    * If you already have a WALFactory, you should favor the instance method.
    * @return a Writer that will overwrite files. Caller must close.
    */
   static Writer createRecoveredEditsWriter(final FileSystem fs, final Path path,
       final Configuration configuration)
       throws IOException {
     return DefaultWALProvider.createWriter(configuration, fs, path, true);
   }
 
   /**
    * If you already have a WALFactory, you should favor the instance method.
    * @return a writer that won't overwrite files. Caller must close.
    */
   @VisibleForTesting
   public static Writer createWALWriter(final FileSystem fs, final Path path,
       final Configuration configuration)
       throws IOException {
     return DefaultWALProvider.createWriter(configuration, fs, path, false);
   }
 
   public final WALProvider getWALProvider() {
     return this.provider;
   }
 
   public final WALProvider getMetaWALProvider() {
     return this.metaProvider.get();
   }
 }