/*
    *
    * 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.regionserver;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.NavigableSet;
  import java.util.UUID;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.regex.Matcher;
  
  import org.apache.commons.collections.map.AbstractReferenceMap;
  import org.apache.commons.collections.map.ReferenceMap;
  import org.apache.commons.lang.ClassUtils;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.commons.math.stat.descriptive.DescriptiveStatistics;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.Coprocessor;
  import org.apache.hadoop.hbase.CoprocessorEnvironment;
  import org.apache.hadoop.hbase.HBaseConfiguration;
  import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.client.Append;
  import org.apache.hadoop.hbase.client.Delete;
  import org.apache.hadoop.hbase.client.Durability;
  import org.apache.hadoop.hbase.client.Get;
  import org.apache.hadoop.hbase.client.Increment;
  import org.apache.hadoop.hbase.client.Mutation;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.hbase.client.Result;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.coprocessor.BaseRegionObserver;
  import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
  import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
  import org.apache.hadoop.hbase.coprocessor.EndpointObserver;
  import org.apache.hadoop.hbase.coprocessor.ObserverContext;
  import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
  import org.apache.hadoop.hbase.coprocessor.RegionObserver;
  import org.apache.hadoop.hbase.coprocessor.RegionObserver.MutationType;
  import org.apache.hadoop.hbase.filter.ByteArrayComparable;
  import org.apache.hadoop.hbase.filter.CompareFilter.CompareOp;
  import org.apache.hadoop.hbase.io.FSDataInputStreamWrapper;
  import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
  import org.apache.hadoop.hbase.io.Reference;
  import org.apache.hadoop.hbase.io.hfile.CacheConfig;
  import org.apache.hadoop.hbase.regionserver.Region.Operation;
  import org.apache.hadoop.hbase.regionserver.compactions.CompactionRequest;
  import org.apache.hadoop.hbase.regionserver.wal.HLogKey;
  import org.apache.hadoop.hbase.wal.WALKey;
  import org.apache.hadoop.hbase.regionserver.wal.WALEdit;
  import org.apache.hadoop.hbase.util.BoundedConcurrentLinkedQueue;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.CoprocessorClassLoader;
  import org.apache.hadoop.hbase.util.Pair;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.Lists;
  import com.google.protobuf.Message;
  import com.google.protobuf.Service;
  
  /**
   * Implements the coprocessor environment and runtime support for coprocessors
   * loaded within a {@link Region}.
   */
  @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
  @InterfaceStability.Evolving
  public class RegionCoprocessorHost
      extends CoprocessorHost<RegionCoprocessorHost.RegionEnvironment> {
  
   private static final Log LOG = LogFactory.getLog(RegionCoprocessorHost.class);
   // The shared data map
   private static ReferenceMap sharedDataMap =
       new ReferenceMap(AbstractReferenceMap.HARD, AbstractReferenceMap.WEAK);
 
   // optimization: no need to call postScannerFilterRow, if no coprocessor implements it
   private final boolean hasCustomPostScannerFilterRow;
 
   /**
    * 
    * Encapsulation of the environment of each coprocessor
    */
   static class RegionEnvironment extends CoprocessorHost.Environment
       implements RegionCoprocessorEnvironment {
 
     private Region region;
     private RegionServerServices rsServices;
     ConcurrentMap<String, Object> sharedData;
     private static final int LATENCY_BUFFER_SIZE = 100;
     private final BoundedConcurrentLinkedQueue<Long> coprocessorTimeNanos =
         new BoundedConcurrentLinkedQueue<Long>(LATENCY_BUFFER_SIZE);
     private final boolean useLegacyPre;
     private final boolean useLegacyPost;
 
     /**
      * Constructor
      * @param impl the coprocessor instance
      * @param priority chaining priority
      */
     public RegionEnvironment(final Coprocessor impl, final int priority,
         final int seq, final Configuration conf, final Region region,
         final RegionServerServices services, final ConcurrentMap<String, Object> sharedData) {
       super(impl, priority, seq, conf);
       this.region = region;
       this.rsServices = services;
       this.sharedData = sharedData;
       // Pick which version of the WAL related events we'll call.
       // This way we avoid calling the new version on older RegionObservers so
       // we can maintain binary compatibility.
       // See notes in javadoc for RegionObserver
       useLegacyPre = useLegacyMethod(impl.getClass(), "preWALRestore", ObserverContext.class,
           HRegionInfo.class, WALKey.class, WALEdit.class);
       useLegacyPost = useLegacyMethod(impl.getClass(), "postWALRestore", ObserverContext.class,
           HRegionInfo.class, WALKey.class, WALEdit.class);
     }
 
     /** @return the region */
     @Override
     public Region getRegion() {
       return region;
     }
 
     /** @return reference to the region server services */
     @Override
     public RegionServerServices getRegionServerServices() {
       return rsServices;
     }
 
     public void shutdown() {
       super.shutdown();
     }
 
     @Override
     public ConcurrentMap<String, Object> getSharedData() {
       return sharedData;
     }
 
     public void offerExecutionLatency(long latencyNanos) {
       coprocessorTimeNanos.offer(latencyNanos);
     }
 
     public Collection<Long> getExecutionLatenciesNanos() {
       final List<Long> latencies = Lists.newArrayListWithCapacity(coprocessorTimeNanos.size());
       coprocessorTimeNanos.drainTo(latencies);
       return latencies;
     }
 
     @Override
     public HRegionInfo getRegionInfo() {
       return region.getRegionInfo();
     }
 
   }
 
   static class TableCoprocessorAttribute {
     private Path path;
     private String className;
     private int priority;
     private Configuration conf;
 
     public TableCoprocessorAttribute(Path path, String className, int priority,
         Configuration conf) {
       this.path = path;
       this.className = className;
       this.priority = priority;
       this.conf = conf;
     }
 
     public Path getPath() {
       return path;
     }
 
     public String getClassName() {
       return className;
     }
 
     public int getPriority() {
       return priority;
     }
 
     public Configuration getConf() {
       return conf;
     }
   }
 
   /** The region server services */
   RegionServerServices rsServices;
   /** The region */
   Region region;
 
   /**
    * Constructor
    * @param region the region
    * @param rsServices interface to available region server functionality
    * @param conf the configuration
    */
   public RegionCoprocessorHost(final Region region,
       final RegionServerServices rsServices, final Configuration conf) {
     super(rsServices);
     this.conf = conf;
     this.rsServices = rsServices;
     this.region = region;
     this.pathPrefix = Integer.toString(this.region.getRegionInfo().hashCode());
 
     // load system default cp's from configuration.
     loadSystemCoprocessors(conf, REGION_COPROCESSOR_CONF_KEY);
 
     // load system default cp's for user tables from configuration.
     if (!region.getRegionInfo().getTable().isSystemTable()) {
       loadSystemCoprocessors(conf, USER_REGION_COPROCESSOR_CONF_KEY);
     }
 
     // load Coprocessor From HDFS
     loadTableCoprocessors(conf);
 
     // now check whether any coprocessor implements postScannerFilterRow
     boolean hasCustomPostScannerFilterRow = false;
     out: for (RegionEnvironment env: coprocessors) {
       if (env.getInstance() instanceof RegionObserver) {
         Class<?> clazz = env.getInstance().getClass();
         for(;;) {
           if (clazz == null) {
             // we must have directly implemented RegionObserver
             hasCustomPostScannerFilterRow = true;
             break out;
           }
           if (clazz == BaseRegionObserver.class) {
             // we reached BaseRegionObserver, try next coprocessor
             break;
           }
           try {
             clazz.getDeclaredMethod("postScannerFilterRow", ObserverContext.class,
               InternalScanner.class, byte[].class, int.class, short.class, boolean.class);
             // this coprocessor has a custom version of postScannerFilterRow
             hasCustomPostScannerFilterRow = true;
             break out;
           } catch (NoSuchMethodException ignore) {
           }
           clazz = clazz.getSuperclass();
         }
       }
     }
     this.hasCustomPostScannerFilterRow = hasCustomPostScannerFilterRow;
   }
 
   static List<TableCoprocessorAttribute> getTableCoprocessorAttrsFromSchema(Configuration conf,
       HTableDescriptor htd) {
     List<TableCoprocessorAttribute> result = Lists.newArrayList();
     for (Map.Entry<ImmutableBytesWritable, ImmutableBytesWritable> e: htd.getValues().entrySet()) {
       String key = Bytes.toString(e.getKey().get()).trim();
       if (HConstants.CP_HTD_ATTR_KEY_PATTERN.matcher(key).matches()) {
         String spec = Bytes.toString(e.getValue().get()).trim();
         // found one
         try {
           Matcher matcher = HConstants.CP_HTD_ATTR_VALUE_PATTERN.matcher(spec);
           if (matcher.matches()) {
             // jar file path can be empty if the cp class can be loaded
             // from class loader.
             Path path = matcher.group(1).trim().isEmpty() ?
                 null : new Path(matcher.group(1).trim());
             String className = matcher.group(2).trim();
             if (className.isEmpty()) {
               LOG.error("Malformed table coprocessor specification: key=" +
                 key + ", spec: " + spec);
               continue;
             }
             int priority = matcher.group(3).trim().isEmpty() ?
                 Coprocessor.PRIORITY_USER : Integer.valueOf(matcher.group(3));
             String cfgSpec = null;
             try {
               cfgSpec = matcher.group(4);
             } catch (IndexOutOfBoundsException ex) {
               // ignore
             }
             Configuration ourConf;
             if (cfgSpec != null && !cfgSpec.trim().equals("|")) {
               cfgSpec = cfgSpec.substring(cfgSpec.indexOf('|') + 1);
               // do an explicit deep copy of the passed configuration
               ourConf = new Configuration(false);
               HBaseConfiguration.merge(ourConf, conf);
               Matcher m = HConstants.CP_HTD_ATTR_VALUE_PARAM_PATTERN.matcher(cfgSpec);
               while (m.find()) {
                 ourConf.set(m.group(1), m.group(2));
               }
             } else {
               ourConf = conf;
             }
             result.add(new TableCoprocessorAttribute(path, className, priority, ourConf));
           } else {
             LOG.error("Malformed table coprocessor specification: key=" + key +
               ", spec: " + spec);
           }
         } catch (Exception ioe) {
           LOG.error("Malformed table coprocessor specification: key=" + key +
             ", spec: " + spec);
         }
       }
     }
     return result;
   }
 
   /**
    * Sanity check the table coprocessor attributes of the supplied schema. Will
    * throw an exception if there is a problem.
    * @param conf
    * @param htd
    * @throws IOException
    */
   public static void testTableCoprocessorAttrs(final Configuration conf,
       final HTableDescriptor htd) throws IOException {
     String pathPrefix = UUID.randomUUID().toString();
     for (TableCoprocessorAttribute attr: getTableCoprocessorAttrsFromSchema(conf, htd)) {
       if (attr.getPriority() < 0) {
         throw new IOException("Priority for coprocessor " + attr.getClassName() +
           " cannot be less than 0");
       }
       ClassLoader old = Thread.currentThread().getContextClassLoader();
       try {
         ClassLoader cl;
         if (attr.getPath() != null) {
           cl = CoprocessorClassLoader.getClassLoader(attr.getPath(),
             CoprocessorHost.class.getClassLoader(), pathPrefix, conf);
         } else {
           cl = CoprocessorHost.class.getClassLoader();
         }
         Thread.currentThread().setContextClassLoader(cl);
         cl.loadClass(attr.getClassName());
       } catch (ClassNotFoundException e) {
         throw new IOException("Class " + attr.getClassName() + " cannot be loaded", e);
       } finally {
         Thread.currentThread().setContextClassLoader(old);
       }
     }
   }
 
   void loadTableCoprocessors(final Configuration conf) {
     boolean coprocessorsEnabled = conf.getBoolean(COPROCESSORS_ENABLED_CONF_KEY,
       DEFAULT_COPROCESSORS_ENABLED);
     boolean tableCoprocessorsEnabled = conf.getBoolean(USER_COPROCESSORS_ENABLED_CONF_KEY,
       DEFAULT_USER_COPROCESSORS_ENABLED);
     if (!(coprocessorsEnabled && tableCoprocessorsEnabled)) {
       return;
     }
 
     // scan the table attributes for coprocessor load specifications
     // initialize the coprocessors
     List<RegionEnvironment> configured = new ArrayList<RegionEnvironment>();
     for (TableCoprocessorAttribute attr: getTableCoprocessorAttrsFromSchema(conf, 
         region.getTableDesc())) {
       // Load encompasses classloading and coprocessor initialization
       try {
         RegionEnvironment env = load(attr.getPath(), attr.getClassName(), attr.getPriority(),
           attr.getConf());
         configured.add(env);
         LOG.info("Loaded coprocessor " + attr.getClassName() + " from HTD of " +
             region.getTableDesc().getTableName().getNameAsString() + " successfully.");
       } catch (Throwable t) {
         // Coprocessor failed to load, do we abort on error?
         if (conf.getBoolean(ABORT_ON_ERROR_KEY, DEFAULT_ABORT_ON_ERROR)) {
           abortServer(attr.getClassName(), t);
         } else {
           LOG.error("Failed to load coprocessor " + attr.getClassName(), t);
         }
       }
     }
     // add together to coprocessor set for COW efficiency
     coprocessors.addAll(configured);
   }
 
   @Override
   public RegionEnvironment createEnvironment(Class<?> implClass,
       Coprocessor instance, int priority, int seq, Configuration conf) {
     // Check if it's an Endpoint.
     // Due to current dynamic protocol design, Endpoint
     // uses a different way to be registered and executed.
     // It uses a visitor pattern to invoke registered Endpoint
     // method.
     for (Object itf : ClassUtils.getAllInterfaces(implClass)) {
       Class<?> c = (Class<?>) itf;
       if (CoprocessorService.class.isAssignableFrom(c)) {
         region.registerService( ((CoprocessorService)instance).getService() );
       }
     }
     ConcurrentMap<String, Object> classData;
     // make sure only one thread can add maps
     synchronized (sharedDataMap) {
       // as long as at least one RegionEnvironment holds on to its classData it will
       // remain in this map
       classData = (ConcurrentMap<String, Object>)sharedDataMap.get(implClass.getName());
       if (classData == null) {
         classData = new ConcurrentHashMap<String, Object>();
         sharedDataMap.put(implClass.getName(), classData);
       }
     }
     return new RegionEnvironment(instance, priority, seq, conf, region,
         rsServices, classData);
   }
 
   /**
    * HBASE-4014 : This is used by coprocessor hooks which are not declared to throw exceptions.
    *
    * For example, {@link
    * org.apache.hadoop.hbase.regionserver.RegionCoprocessorHost#preOpen()} and
    * {@link org.apache.hadoop.hbase.regionserver.RegionCoprocessorHost#postOpen()} are such hooks.
    *
    * See also
    * {@link org.apache.hadoop.hbase.master.MasterCoprocessorHost#handleCoprocessorThrowable(
    *    CoprocessorEnvironment, Throwable)}
    * @param env The coprocessor that threw the exception.
    * @param e The exception that was thrown.
    */
   private void handleCoprocessorThrowableNoRethrow(
       final CoprocessorEnvironment env, final Throwable e) {
     try {
       handleCoprocessorThrowable(env,e);
     } catch (IOException ioe) {
       // We cannot throw exceptions from the caller hook, so ignore.
       LOG.warn(
         "handleCoprocessorThrowable() threw an IOException while attempting to handle Throwable " +
         e + ". Ignoring.",e);
     }
   }
 
   /**
    * Invoked before a region open.
    *
    * @throws IOException Signals that an I/O exception has occurred.
    */
   public void preOpen() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preOpen(ctx);
       }
     });
   }
 
   /**
    * Invoked after a region open
    */
   public void postOpen() {
     try {
       execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
         @Override
         public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
             throws IOException {
           oserver.postOpen(ctx);
         }
       });
     } catch (IOException e) {
       LOG.warn(e);
     }
   }
 
   /**
    * Invoked after log replay on region
    */
   public void postLogReplay() {
     try {
       execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
         @Override
         public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
             throws IOException {
           oserver.postLogReplay(ctx);
         }
       });
     } catch (IOException e) {
       LOG.warn(e);
     }
   }
 
   /**
    * Invoked before a region is closed
    * @param abortRequested true if the server is aborting
    */
   public void preClose(final boolean abortRequested) throws IOException {
     execOperation(false, new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preClose(ctx, abortRequested);
       }
     });
   }
 
   /**
    * Invoked after a region is closed
    * @param abortRequested true if the server is aborting
    */
   public void postClose(final boolean abortRequested) {
     try {
       execOperation(false, new RegionOperation() {
         @Override
         public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
             throws IOException {
           oserver.postClose(ctx, abortRequested);
         }
         public void postEnvCall(RegionEnvironment env) {
           shutdown(env);
         }
       });
     } catch (IOException e) {
       LOG.warn(e);
     }
   }
 
   /**
    * See
    * {@link RegionObserver#preCompactScannerOpen(ObserverContext, Store, List, ScanType, long, InternalScanner, CompactionRequest)}
    */
   public InternalScanner preCompactScannerOpen(final Store store,
       final List<StoreFileScanner> scanners, final ScanType scanType, final long earliestPutTs,
       final CompactionRequest request) throws IOException {
     return execOperationWithResult(null,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<InternalScanner>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preCompactScannerOpen(ctx, store, scanners, scanType,
           earliestPutTs, getResult(), request));
       }
     });
   }
 
   /**
    * Called prior to selecting the {@link StoreFile}s for compaction from the list of currently
    * available candidates.
    * @param store The store where compaction is being requested
    * @param candidates The currently available store files
    * @param request custom compaction request
    * @return If {@code true}, skip the normal selection process and use the current list
    * @throws IOException
    */
   public boolean preCompactSelection(final Store store, final List<StoreFile> candidates,
       final CompactionRequest request) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preCompactSelection(ctx, store, candidates, request);
       }
     });
   }
 
   /**
    * Called after the {@link StoreFile}s to be compacted have been selected from the available
    * candidates.
    * @param store The store where compaction is being requested
    * @param selected The store files selected to compact
    * @param request custom compaction
    */
   public void postCompactSelection(final Store store, final ImmutableList<StoreFile> selected,
       final CompactionRequest request) {
     try {
       execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
         @Override
         public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
             throws IOException {
           oserver.postCompactSelection(ctx, store, selected, request);
         }
       });
     } catch (IOException e) {
       LOG.warn(e);
     }
   }
 
   /**
    * Called prior to rewriting the store files selected for compaction
    * @param store the store being compacted
    * @param scanner the scanner used to read store data during compaction
    * @param scanType type of Scan
    * @param request the compaction that will be executed
    * @throws IOException
    */
   public InternalScanner preCompact(final Store store, final InternalScanner scanner,
       final ScanType scanType, final CompactionRequest request) throws IOException {
     return execOperationWithResult(false, scanner,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<InternalScanner>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preCompact(ctx, store, getResult(), scanType, request));
       }
     });
   }
 
   /**
    * Called after the store compaction has completed.
    * @param store the store being compacted
    * @param resultFile the new store file written during compaction
    * @param request the compaction that is being executed
    * @throws IOException
    */
   public void postCompact(final Store store, final StoreFile resultFile,
       final CompactionRequest request) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postCompact(ctx, store, resultFile, request);
       }
     });
   }
 
   /**
    * Invoked before a memstore flush
    * @throws IOException
    */
   public InternalScanner preFlush(final Store store, final InternalScanner scanner)
       throws IOException {
     return execOperationWithResult(false, scanner,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<InternalScanner>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preFlush(ctx, store, getResult()));
       }
     });
   }
 
   /**
    * Invoked before a memstore flush
    * @throws IOException
    */
   public void preFlush() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preFlush(ctx);
       }
     });
   }
 
   /**
    * See
    * {@link RegionObserver#preFlushScannerOpen(ObserverContext,
    *    Store, KeyValueScanner, InternalScanner)}
    */
   public InternalScanner preFlushScannerOpen(final Store store,
       final KeyValueScanner memstoreScanner) throws IOException {
     return execOperationWithResult(null,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<InternalScanner>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preFlushScannerOpen(ctx, store, memstoreScanner, getResult()));
       }
     });
   }
 
   /**
    * Invoked after a memstore flush
    * @throws IOException
    */
   public void postFlush() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postFlush(ctx);
       }
     });
   }
 
   /**
    * Invoked after a memstore flush
    * @throws IOException
    */
   public void postFlush(final Store store, final StoreFile storeFile) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postFlush(ctx, store, storeFile);
       }
     });
   }
 
   /**
    * Invoked just before a split
    * @throws IOException
    */
   // TODO: Deprecate this
   public void preSplit() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSplit(ctx);
       }
     });
   }
 
   /**
    * Invoked just before a split
    * @throws IOException
    */
   public void preSplit(final byte[] splitRow) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSplit(ctx, splitRow);
       }
     });
   }
 
   /**
    * Invoked just after a split
    * @param l the new left-hand daughter region
    * @param r the new right-hand daughter region
    * @throws IOException
    */
   public void postSplit(final Region l, final Region r) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postSplit(ctx, l, r);
       }
     });
   }
 
   public boolean preSplitBeforePONR(final byte[] splitKey,
       final List<Mutation> metaEntries) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSplitBeforePONR(ctx, splitKey, metaEntries);
       }
     });
   }
 
   public void preSplitAfterPONR() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSplitAfterPONR(ctx);
       }
     });
   }
 
   /**
    * Invoked just before the rollback of a failed split is started
    * @throws IOException
    */
   public void preRollBackSplit() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preRollBackSplit(ctx);
       }
     });
   }
 
   /**
    * Invoked just after the rollback of a failed split is done
    * @throws IOException
    */
   public void postRollBackSplit() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postRollBackSplit(ctx);
       }
     });
   }
 
   /**
    * Invoked after a split is completed irrespective of a failure or success.
    * @throws IOException
    */
   public void postCompleteSplit() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postCompleteSplit(ctx);
       }
     });
   }
 
   // RegionObserver support
 
   /**
    * @param row the row key
    * @param family the family
    * @param result the result set from the region
    * @return true if default processing should be bypassed
    * @exception IOException Exception
    */
   public boolean preGetClosestRowBefore(final byte[] row, final byte[] family,
       final Result result) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preGetClosestRowBefore(ctx, row, family, result);
       }
     });
   }
 
   /**
    * @param row the row key
    * @param family the family
    * @param result the result set from the region
    * @exception IOException Exception
    */
   public void postGetClosestRowBefore(final byte[] row, final byte[] family,
       final Result result) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postGetClosestRowBefore(ctx, row, family, result);
       }
     });
   }
 
   /**
    * @param get the Get request
    * @return true if default processing should be bypassed
    * @exception IOException Exception
    */
   public boolean preGet(final Get get, final List<Cell> results)
       throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preGetOp(ctx, get, results);
       }
     });
   }
 
   /**
    * @param get the Get request
    * @param results the result sett
    * @exception IOException Exception
    */
   public void postGet(final Get get, final List<Cell> results)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postGetOp(ctx, get, results);
       }
     });
   }
 
   /**
    * @param get the Get request
    * @return true or false to return to client if bypassing normal operation,
    * or null otherwise
    * @exception IOException Exception
    */
   public Boolean preExists(final Get get) throws IOException {
     return execOperationWithResult(true, false,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preExists(ctx, get, getResult()));
       }
     });
   }
 
   /**
    * @param get the Get request
    * @param exists the result returned by the region server
    * @return the result to return to the client
    * @exception IOException Exception
    */
   public boolean postExists(final Get get, boolean exists)
       throws IOException {
     return execOperationWithResult(exists,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postExists(ctx, get, getResult()));
       }
     });
   }
 
   /**
    * @param put The Put object
    * @param edit The WALEdit object.
    * @param durability The durability used
    * @return true if default processing should be bypassed
    * @exception IOException Exception
    */
   public boolean prePut(final Put put, final WALEdit edit, final Durability durability)
       throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.prePut(ctx, put, edit, durability);
       }
     });
   }
 
   /**
    * @param mutation - the current mutation
    * @param kv - the current cell
    * @param byteNow - current timestamp in bytes
    * @param get - the get that could be used
    * Note that the get only does not specify the family and qualifier that should be used
    * @return true if default processing should be bypassed
    * @exception IOException
    *              Exception
    */
   public boolean prePrepareTimeStampForDeleteVersion(final Mutation mutation,
       final Cell kv, final byte[] byteNow, final Get get) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.prePrepareTimeStampForDeleteVersion(ctx, mutation, kv, byteNow, get);
       }
     });
   }
 
   /**
    * @param put The Put object
    * @param edit The WALEdit object.
    * @param durability The durability used
    * @exception IOException Exception
    */
   public void postPut(final Put put, final WALEdit edit, final Durability durability)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postPut(ctx, put, edit, durability);
       }
     });
   }
 
   /**
    * @param delete The Delete object
    * @param edit The WALEdit object.
    * @param durability The durability used
    * @return true if default processing should be bypassed
    * @exception IOException Exception
    */
   public boolean preDelete(final Delete delete, final WALEdit edit, final Durability durability)
       throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preDelete(ctx, delete, edit, durability);
       }
     });
   }
 
   /**
    * @param delete The Delete object
    * @param edit The WALEdit object.
    * @param durability The durability used
    * @exception IOException Exception
    */
   public void postDelete(final Delete delete, final WALEdit edit, final Durability durability)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postDelete(ctx, delete, edit, durability);
       }
     });
   }
 
   /**
    * @param miniBatchOp
    * @return true if default processing should be bypassed
    * @throws IOException
    */
   public boolean preBatchMutate(
       final MiniBatchOperationInProgress<Mutation> miniBatchOp) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preBatchMutate(ctx, miniBatchOp);
       }
     });
   }
 
   /**
    * @param miniBatchOp
    * @throws IOException
    */
   public void postBatchMutate(
       final MiniBatchOperationInProgress<Mutation> miniBatchOp) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postBatchMutate(ctx, miniBatchOp);
       }
     });
   }
 
   public void postBatchMutateIndispensably(
       final MiniBatchOperationInProgress<Mutation> miniBatchOp, final boolean success)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postBatchMutateIndispensably(ctx, miniBatchOp, success);
       }
     });
   }
 
   /**
    * @param row row to check
    * @param family column family
    * @param qualifier column qualifier
    * @param compareOp the comparison operation
    * @param comparator the comparator
    * @param put data to put if check succeeds
    * @return true or false to return to client if default processing should
    * be bypassed, or null otherwise
    * @throws IOException e
    */
   public Boolean preCheckAndPut(final byte [] row, final byte [] family,
       final byte [] qualifier, final CompareOp compareOp,
       final ByteArrayComparable comparator, final Put put)
       throws IOException {
     return execOperationWithResult(true, false,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preCheckAndPut(ctx, row, family, qualifier,
           compareOp, comparator, put, getResult()));
       }
     });
   }
 
   /**
    * @param row row to check
    * @param family column family
    * @param qualifier column qualifier
    * @param compareOp the comparison operation
    * @param comparator the comparator
    * @param put data to put if check succeeds
    * @return true or false to return to client if default processing should
    * be bypassed, or null otherwise
    * @throws IOException e
    */
   public Boolean preCheckAndPutAfterRowLock(final byte[] row, final byte[] family,
       final byte[] qualifier, final CompareOp compareOp, final ByteArrayComparable comparator,
       final Put put) throws IOException {
     return execOperationWithResult(true, false,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preCheckAndPutAfterRowLock(ctx, row, family, qualifier,
           compareOp, comparator, put, getResult()));
       }
     });
   }
 
   /**
    * @param row row to check
    * @param family column family
    * @param qualifier column qualifier
    * @param compareOp the comparison operation
    * @param comparator the comparator
    * @param put data to put if check succeeds
    * @throws IOException e
    */
   public boolean postCheckAndPut(final byte [] row, final byte [] family,
       final byte [] qualifier, final CompareOp compareOp,
       final ByteArrayComparable comparator, final Put put,
       boolean result) throws IOException {
     return execOperationWithResult(result,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postCheckAndPut(ctx, row, family, qualifier,
           compareOp, comparator, put, getResult()));
       }
     });
   }
 
   /**
    * @param row row to check
    * @param family column family
    * @param qualifier column qualifier
    * @param compareOp the comparison operation
    * @param comparator the comparator
    * @param delete delete to commit if check succeeds
    * @return true or false to return to client if default processing should
    * be bypassed, or null otherwise
    * @throws IOException e
    */
   public Boolean preCheckAndDelete(final byte [] row, final byte [] family,
       final byte [] qualifier, final CompareOp compareOp,
       final ByteArrayComparable comparator, final Delete delete)
       throws IOException {
     return execOperationWithResult(true, false,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preCheckAndDelete(ctx, row, family,
             qualifier, compareOp, comparator, delete, getResult()));
       }
     });
   }
 
   /**
    * @param row row to check
    * @param family column family
    * @param qualifier column qualifier
    * @param compareOp the comparison operation
    * @param comparator the comparator
    * @param delete delete to commit if check succeeds
    * @return true or false to return to client if default processing should
    * be bypassed, or null otherwise
    * @throws IOException e
    */
   public Boolean preCheckAndDeleteAfterRowLock(final byte[] row, final byte[] family,
       final byte[] qualifier, final CompareOp compareOp, final ByteArrayComparable comparator,
       final Delete delete) throws IOException {
     return execOperationWithResult(true, false,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preCheckAndDeleteAfterRowLock(ctx, row,
               family, qualifier, compareOp, comparator, delete, getResult()));
       }
     });
   }
 
   /**
    * @param row row to check
    * @param family column family
    * @param qualifier column qualifier
    * @param compareOp the comparison operation
    * @param comparator the comparator
    * @param delete delete to commit if check succeeds
    * @throws IOException e
    */
   public boolean postCheckAndDelete(final byte [] row, final byte [] family,
       final byte [] qualifier, final CompareOp compareOp,
       final ByteArrayComparable comparator, final Delete delete,
       boolean result) throws IOException {
     return execOperationWithResult(result,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postCheckAndDelete(ctx, row, family,
             qualifier, compareOp, comparator, delete, getResult()));
       }
     });
   }
 
   /**
    * @param append append object
    * @return result to return to client if default operation should be
    * bypassed, null otherwise
    * @throws IOException if an error occurred on the coprocessor
    */
   public Result preAppend(final Append append) throws IOException {
     return execOperationWithResult(true, null,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Result>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preAppend(ctx, append));
       }
     });
   }
 
   /**
    * @param append append object
    * @return result to return to client if default operation should be
    * bypassed, null otherwise
    * @throws IOException if an error occurred on the coprocessor
    */
   public Result preAppendAfterRowLock(final Append append) throws IOException {
     return execOperationWithResult(true, null,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Result>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preAppendAfterRowLock(ctx, append));
       }
     });
   }
 
   /**
    * @param increment increment object
    * @return result to return to client if default operation should be
    * bypassed, null otherwise
    * @throws IOException if an error occurred on the coprocessor
    */
   public Result preIncrement(final Increment increment) throws IOException {
     return execOperationWithResult(true, null,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Result>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preIncrement(ctx, increment));
       }
     });
   }
 
   /**
    * @param increment increment object
    * @return result to return to client if default operation should be
    * bypassed, null otherwise
    * @throws IOException if an error occurred on the coprocessor
    */
   public Result preIncrementAfterRowLock(final Increment increment) throws IOException {
     return execOperationWithResult(true, null,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Result>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preIncrementAfterRowLock(ctx, increment));
       }
     });
   }
 
   /**
    * @param append Append object
    * @param result the result returned by the append
    * @throws IOException if an error occurred on the coprocessor
    */
   public void postAppend(final Append append, final Result result) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postAppend(ctx, append, result);
       }
     });
   }
 
   /**
    * @param increment increment object
    * @param result the result returned by postIncrement
    * @throws IOException if an error occurred on the coprocessor
    */
   public Result postIncrement(final Increment increment, Result result) throws IOException {
     return execOperationWithResult(result,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Result>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postIncrement(ctx, increment, getResult()));
       }
     });
   }
 
   /**
    * @param scan the Scan specification
    * @return scanner id to return to client if default operation should be
    * bypassed, false otherwise
    * @exception IOException Exception
    */
   public RegionScanner preScannerOpen(final Scan scan) throws IOException {
     return execOperationWithResult(true, null,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<RegionScanner>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preScannerOpen(ctx, scan, getResult()));
       }
     });
   }
 
   /**
    * See
    * {@link RegionObserver#preStoreScannerOpen(ObserverContext,
    *    Store, Scan, NavigableSet, KeyValueScanner)}
    */
   public KeyValueScanner preStoreScannerOpen(final Store store, final Scan scan,
       final NavigableSet<byte[]> targetCols) throws IOException {
     return execOperationWithResult(null,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<KeyValueScanner>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preStoreScannerOpen(ctx, store, scan, targetCols, getResult()));
       }
     });
   }
 
   /**
    * @param scan the Scan specification
    * @param s the scanner
    * @return the scanner instance to use
    * @exception IOException Exception
    */
   public RegionScanner postScannerOpen(final Scan scan, RegionScanner s) throws IOException {
     return execOperationWithResult(s,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<RegionScanner>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postScannerOpen(ctx, scan, getResult()));
       }
     });
   }
 
   /**
    * @param s the scanner
    * @param results the result set returned by the region server
    * @param limit the maximum number of results to return
    * @return 'has next' indication to client if bypassing default behavior, or
    * null otherwise
    * @exception IOException Exception
    */
   public Boolean preScannerNext(final InternalScanner s,
       final List<Result> results, final int limit) throws IOException {
     return execOperationWithResult(true, false,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preScannerNext(ctx, s, results, limit, getResult()));
       }
     });
   }
 
   /**
    * @param s the scanner
    * @param results the result set returned by the region server
    * @param limit the maximum number of results to return
    * @param hasMore
    * @return 'has more' indication to give to client
    * @exception IOException Exception
    */
   public boolean postScannerNext(final InternalScanner s,
       final List<Result> results, final int limit, boolean hasMore)
       throws IOException {
     return execOperationWithResult(hasMore,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postScannerNext(ctx, s, results, limit, getResult()));
       }
     });
   }
 
   /**
    * This will be called by the scan flow when the current scanned row is being filtered out by the
    * filter.
    * @param s the scanner
    * @param currentRow The current rowkey which got filtered out
    * @param offset offset to rowkey
    * @param length length of rowkey
    * @return whether more rows are available for the scanner or not
    * @throws IOException
    */
   public boolean postScannerFilterRow(final InternalScanner s, final byte[] currentRow,
       final int offset, final short length) throws IOException {
     // short circuit for performance
     if (!hasCustomPostScannerFilterRow) return true;
     return execOperationWithResult(true,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postScannerFilterRow(ctx, s, currentRow, offset,length, getResult()));
       }
     });
   }
 
   /**
    * @param s the scanner
    * @return true if default behavior should be bypassed, false otherwise
    * @exception IOException Exception
    */
   public boolean preScannerClose(final InternalScanner s) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preScannerClose(ctx, s);
       }
     });
   }
 
   /**
    * @exception IOException Exception
    */
   public void postScannerClose(final InternalScanner s) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postScannerClose(ctx, s);
       }
     });
   }
 
   /**
    * @param info
    * @param logKey
    * @param logEdit
    * @return true if default behavior should be bypassed, false otherwise
    * @throws IOException
    */
   public boolean preWALRestore(final HRegionInfo info, final WALKey logKey,
       final WALEdit logEdit) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         // Once we don't need to support the legacy call, replace RegionOperation with a version
         // that's ObserverContext<RegionEnvironment> and avoid this cast.
         final RegionEnvironment env = (RegionEnvironment)ctx.getEnvironment();
         if (env.useLegacyPre) {
           if (logKey instanceof HLogKey) {
             oserver.preWALRestore(ctx, info, (HLogKey)logKey, logEdit);
           } else {
             legacyWarning(oserver.getClass(), "There are wal keys present that are not HLogKey.");
           }
         } else {
           oserver.preWALRestore(ctx, info, logKey, logEdit);
         }
       }
     });
   }
 
   /**
    * @return true if default behavior should be bypassed, false otherwise
    * @deprecated use {@link #preWALRestore(HRegionInfo, WALKey, WALEdit)}
    */
   @Deprecated
   public boolean preWALRestore(final HRegionInfo info, final HLogKey logKey,
       final WALEdit logEdit) throws IOException {
     return preWALRestore(info, (WALKey)logKey, logEdit);
   }
 
   /**
    * @param info
    * @param logKey
    * @param logEdit
    * @throws IOException
    */
   public void postWALRestore(final HRegionInfo info, final WALKey logKey, final WALEdit logEdit)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         // Once we don't need to support the legacy call, replace RegionOperation with a version
         // that's ObserverContext<RegionEnvironment> and avoid this cast.
         final RegionEnvironment env = (RegionEnvironment)ctx.getEnvironment();
         if (env.useLegacyPost) {
           if (logKey instanceof HLogKey) {
             oserver.postWALRestore(ctx, info, (HLogKey)logKey, logEdit);
           } else {
             legacyWarning(oserver.getClass(), "There are wal keys present that are not HLogKey.");
           }
         } else {
           oserver.postWALRestore(ctx, info, logKey, logEdit);
         }
       }
     });
   }
 
   /**
    * @deprecated use {@link #postWALRestore(HRegionInfo, WALKey, WALEdit)}
    */
   @Deprecated
   public void postWALRestore(final HRegionInfo info, final HLogKey logKey, final WALEdit logEdit)
       throws IOException {
     postWALRestore(info, (WALKey)logKey, logEdit);
   }
 
   /**
    * @param familyPaths pairs of { CF, file path } submitted for bulk load
    * @return true if the default operation should be bypassed
    * @throws IOException
    */
   public boolean preBulkLoadHFile(final List<Pair<byte[], String>> familyPaths) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preBulkLoadHFile(ctx, familyPaths);
       }
     });
   }
 
   /**
    * @param familyPaths pairs of { CF, file path } submitted for bulk load
    * @param hasLoaded whether load was successful or not
    * @return the possibly modified value of hasLoaded
    * @throws IOException
    */
   public boolean postBulkLoadHFile(final List<Pair<byte[], String>> familyPaths,
       boolean hasLoaded) throws IOException {
     return execOperationWithResult(hasLoaded,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Boolean>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postBulkLoadHFile(ctx, familyPaths, getResult()));
       }
     });
   }
 
   public void postStartRegionOperation(final Operation op) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postStartRegionOperation(ctx, op);
       }
     });
   }
 
   public void postCloseRegionOperation(final Operation op) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postCloseRegionOperation(ctx, op);
       }
     });
   }
 
   /**
    * @param fs fileystem to read from
    * @param p path to the file
    * @param in {@link FSDataInputStreamWrapper}
    * @param size Full size of the file
    * @param cacheConf
    * @param r original reference file. This will be not null only when reading a split file.
    * @return a Reader instance to use instead of the base reader if overriding
    * default behavior, null otherwise
    * @throws IOException
    */
   public StoreFile.Reader preStoreFileReaderOpen(final FileSystem fs, final Path p,
       final FSDataInputStreamWrapper in, final long size, final CacheConfig cacheConf,
       final Reference r) throws IOException {
     return execOperationWithResult(null,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<StoreFile.Reader>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preStoreFileReaderOpen(ctx, fs, p, in, size, cacheConf, r, getResult()));
       }
     });
   }
 
   /**
    * @param fs fileystem to read from
    * @param p path to the file
    * @param in {@link FSDataInputStreamWrapper}
    * @param size Full size of the file
    * @param cacheConf
    * @param r original reference file. This will be not null only when reading a split file.
    * @param reader the base reader instance
    * @return The reader to use
    * @throws IOException
    */
   public StoreFile.Reader postStoreFileReaderOpen(final FileSystem fs, final Path p,
       final FSDataInputStreamWrapper in, final long size, final CacheConfig cacheConf,
       final Reference r, final StoreFile.Reader reader) throws IOException {
     return execOperationWithResult(reader,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<StoreFile.Reader>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postStoreFileReaderOpen(ctx, fs, p, in, size, cacheConf, r, getResult()));
       }
     });
   }
 
   public Cell postMutationBeforeWAL(final MutationType opType, final Mutation mutation,
       final Cell oldCell, Cell newCell) throws IOException {
     return execOperationWithResult(newCell,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<Cell>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postMutationBeforeWAL(ctx, opType, mutation, oldCell, getResult()));
       }
     });
   }
 
   public Message preEndpointInvocation(final Service service, final String methodName,
       Message request) throws IOException {
     return execOperationWithResult(request,
         coprocessors.isEmpty() ? null : new EndpointOperationWithResult<Message>() {
       @Override
       public void call(EndpointObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preEndpointInvocation(ctx, service, methodName, getResult()));
       }
     });
   }
 
   public void postEndpointInvocation(final Service service, final String methodName,
       final Message request, final Message.Builder responseBuilder) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new EndpointOperation() {
       @Override
       public void call(EndpointObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postEndpointInvocation(ctx, service, methodName, request, responseBuilder);
       }
     });
   }
 
   public DeleteTracker postInstantiateDeleteTracker(DeleteTracker tracker) throws IOException {
     return execOperationWithResult(tracker,
         coprocessors.isEmpty() ? null : new RegionOperationWithResult<DeleteTracker>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.postInstantiateDeleteTracker(ctx, getResult()));
       }
     });
   }
 
   public Map<String, DescriptiveStatistics> getCoprocessorExecutionStatistics() {
     Map<String, DescriptiveStatistics> results = new HashMap<String, DescriptiveStatistics>();
     for (RegionEnvironment env : coprocessors) {
       DescriptiveStatistics ds = new DescriptiveStatistics();
       if (env.getInstance() instanceof RegionObserver) {
         for (Long time : env.getExecutionLatenciesNanos()) {
           ds.addValue(time);
         }
         // Ensures that web ui circumvents the display of NaN values when there are zero samples.
         if (ds.getN() == 0) {
           ds.addValue(0);
         }
         results.put(env.getInstance().getClass().getSimpleName(), ds);
       }
     }
     return results;
   }
 
   private static abstract class CoprocessorOperation
       extends ObserverContext<RegionCoprocessorEnvironment> {
     public abstract void call(Coprocessor observer,
         ObserverContext<RegionCoprocessorEnvironment> ctx) throws IOException;
     public abstract boolean hasCall(Coprocessor observer);
     public void postEnvCall(RegionEnvironment env) { }
   }
 
   private static abstract class RegionOperation extends CoprocessorOperation {
     public abstract void call(RegionObserver observer,
         ObserverContext<RegionCoprocessorEnvironment> ctx) throws IOException;
 
     public boolean hasCall(Coprocessor observer) {
       return observer instanceof RegionObserver;
     }
 
     public void call(Coprocessor observer, ObserverContext<RegionCoprocessorEnvironment> ctx)
         throws IOException {
       call((RegionObserver)observer, ctx);
     }
   }
 
   private static abstract class RegionOperationWithResult<T> extends RegionOperation {
     private T result = null;
     public void setResult(final T result) { this.result = result; }
     public T getResult() { return this.result; }
   }
 
   private static abstract class EndpointOperation extends CoprocessorOperation {
     public abstract void call(EndpointObserver observer,
         ObserverContext<RegionCoprocessorEnvironment> ctx) throws IOException;
 
     public boolean hasCall(Coprocessor observer) {
       return observer instanceof EndpointObserver;
     }
 
     public void call(Coprocessor observer, ObserverContext<RegionCoprocessorEnvironment> ctx)
         throws IOException {
       call((EndpointObserver)observer, ctx);
     }
   }
 
   private static abstract class EndpointOperationWithResult<T> extends EndpointOperation {
     private T result = null;
     public void setResult(final T result) { this.result = result; }
     public T getResult() { return this.result; }
   }
 
   private boolean execOperation(final CoprocessorOperation ctx)
       throws IOException {
     return execOperation(true, ctx);
   }
 
   private <T> T execOperationWithResult(final T defaultValue,
       final RegionOperationWithResult<T> ctx) throws IOException {
     if (ctx == null) return defaultValue;
     ctx.setResult(defaultValue);
     execOperation(true, ctx);
     return ctx.getResult();
   }
 
   private <T> T execOperationWithResult(final boolean ifBypass, final T defaultValue,
       final RegionOperationWithResult<T> ctx) throws IOException {
     boolean bypass = false;
     T result = defaultValue;
     if (ctx != null) {
       ctx.setResult(defaultValue);
       bypass = execOperation(true, ctx);
       result = ctx.getResult();
     }
     return bypass == ifBypass ? result : null;
   }
 
   private <T> T execOperationWithResult(final T defaultValue,
       final EndpointOperationWithResult<T> ctx) throws IOException {
     if (ctx == null) return defaultValue;
     ctx.setResult(defaultValue);
     execOperation(true, ctx);
     return ctx.getResult();
   }
 
   private boolean execOperation(final boolean earlyExit, final CoprocessorOperation ctx)
       throws IOException {
     boolean bypass = false;
     for (RegionEnvironment env: coprocessors) {
       Coprocessor observer = env.getInstance();
       if (ctx.hasCall(observer)) {
         long startTime = System.nanoTime();
         ctx.prepare(env);
         Thread currentThread = Thread.currentThread();
         ClassLoader cl = currentThread.getContextClassLoader();
         try {
           currentThread.setContextClassLoader(env.getClassLoader());
           ctx.call(observer, ctx);
         } catch (Throwable e) {
           handleCoprocessorThrowable(env, e);
         } finally {
           currentThread.setContextClassLoader(cl);
         }
         env.offerExecutionLatency(System.nanoTime() - startTime);
         bypass |= ctx.shouldBypass();
         if (earlyExit && ctx.shouldComplete()) {
           break;
         }
       }
 
       ctx.postEnvCall(env);
     }
     return bypass;
   }
 }