/*
    *
    * 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.master;
  
  import java.io.IOException;
  import java.util.List;
  
  import org.apache.commons.lang.ClassUtils;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.Coprocessor;
  import org.apache.hadoop.hbase.HColumnDescriptor;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.NamespaceDescriptor;
  import org.apache.hadoop.hbase.ProcedureInfo;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.client.Admin;
  import org.apache.hadoop.hbase.coprocessor.*;
  import org.apache.hadoop.hbase.master.procedure.MasterProcedureEnv;
  import org.apache.hadoop.hbase.procedure2.ProcedureExecutor;
  import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.SnapshotDescription;
  import org.apache.hadoop.hbase.protobuf.generated.QuotaProtos.Quotas;
  
  /**
   * Provides the coprocessor framework and environment for master oriented
   * operations.  {@link HMaster} interacts with the loaded coprocessors
   * through this class.
   */
  @InterfaceAudience.Private
  public class MasterCoprocessorHost
      extends CoprocessorHost<MasterCoprocessorHost.MasterEnvironment> {
  
    private static final Log LOG = LogFactory.getLog(MasterCoprocessorHost.class);
  
    /**
     * Coprocessor environment extension providing access to master related
     * services.
     */
    static class MasterEnvironment extends CoprocessorHost.Environment
        implements MasterCoprocessorEnvironment {
      private MasterServices masterServices;
  
      public MasterEnvironment(final Class<?> implClass, final Coprocessor impl,
          final int priority, final int seq, final Configuration conf,
          final MasterServices services) {
        super(impl, priority, seq, conf);
        this.masterServices = services;
      }
  
      public MasterServices getMasterServices() {
        return masterServices;
      }
    }
  
    private MasterServices masterServices;
  
    public MasterCoprocessorHost(final MasterServices services, final Configuration conf) {
      super(services);
      this.conf = conf;
      this.masterServices = services;
      // Log the state of coprocessor loading here; should appear only once or
      // twice in the daemon log, depending on HBase version, because there is
      // only one MasterCoprocessorHost instance in the master process
      boolean coprocessorsEnabled = conf.getBoolean(COPROCESSORS_ENABLED_CONF_KEY,
        DEFAULT_COPROCESSORS_ENABLED);
      LOG.info("System coprocessor loading is " + (coprocessorsEnabled ? "enabled" : "disabled"));
      loadSystemCoprocessors(conf, MASTER_COPROCESSOR_CONF_KEY);
    }
  
    @Override
    public MasterEnvironment createEnvironment(final Class<?> implClass,
        final Coprocessor instance, final int priority, final int seq,
        final Configuration conf) {
      for (Object itf : ClassUtils.getAllInterfaces(implClass)) {
        Class<?> c = (Class<?>) itf;
        if (CoprocessorService.class.isAssignableFrom(c)) {
          masterServices.registerService(((CoprocessorService)instance).getService());
        }
     }
     return new MasterEnvironment(implClass, instance, priority, seq, conf,
         masterServices);
   }
 
   public boolean preCreateNamespace(final NamespaceDescriptor ns) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preCreateNamespace(ctx, ns);
       }
     });
   }
 
   public void postCreateNamespace(final NamespaceDescriptor ns) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postCreateNamespace(ctx, ns);
       }
     });
   }
 
   public boolean preDeleteNamespace(final String namespaceName) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preDeleteNamespace(ctx, namespaceName);
       }
     });
   }
 
   public void postDeleteNamespace(final String namespaceName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postDeleteNamespace(ctx, namespaceName);
       }
     });
   }
 
   public boolean preModifyNamespace(final NamespaceDescriptor ns) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preModifyNamespace(ctx, ns);
       }
     });
   }
 
   public void postModifyNamespace(final NamespaceDescriptor ns) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postModifyNamespace(ctx, ns);
       }
     });
   }
 
   public void preGetNamespaceDescriptor(final String namespaceName)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preGetNamespaceDescriptor(ctx, namespaceName);
       }
     });
   }
 
   public void postGetNamespaceDescriptor(final NamespaceDescriptor ns)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postGetNamespaceDescriptor(ctx, ns);
       }
     });
   }
 
   public boolean preListNamespaceDescriptors(final List<NamespaceDescriptor> descriptors)
       throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preListNamespaceDescriptors(ctx, descriptors);
       }
     });
   }
 
   public void postListNamespaceDescriptors(final List<NamespaceDescriptor> descriptors)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postListNamespaceDescriptors(ctx, descriptors);
       }
     });
   }
 
   /* Implementation of hooks for invoking MasterObservers */
 
   public void preCreateTable(final HTableDescriptor htd, final HRegionInfo[] regions)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preCreateTable(ctx, htd, regions);
       }
     });
   }
 
   public void postCreateTable(final HTableDescriptor htd, final HRegionInfo[] regions)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postCreateTable(ctx, htd, regions);
       }
     });
   }
 
   public void preCreateTableHandler(final HTableDescriptor htd, final HRegionInfo[] regions)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preCreateTableHandler(ctx, htd, regions);
       }
     });
   }
 
   public void postCreateTableHandler(final HTableDescriptor htd, final HRegionInfo[] regions)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postCreateTableHandler(ctx, htd, regions);
       }
     });
   }
 
   public void preDeleteTable(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preDeleteTable(ctx, tableName);
       }
     });
   }
 
   public void postDeleteTable(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postDeleteTable(ctx, tableName);
       }
     });
   }
 
   public void preDeleteTableHandler(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preDeleteTableHandler(ctx, tableName);
       }
     });
   }
 
   public void postDeleteTableHandler(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postDeleteTableHandler(ctx, tableName);
       }
     });
   }
 
   public void preTruncateTable(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preTruncateTable(ctx, tableName);
       }
     });
   }
 
   public void postTruncateTable(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postTruncateTable(ctx, tableName);
       }
     });
   }
 
   public void preTruncateTableHandler(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preTruncateTableHandler(ctx, tableName);
       }
     });
   }
 
   public void postTruncateTableHandler(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postTruncateTableHandler(ctx, tableName);
       }
     });
   }
 
   public void preModifyTable(final TableName tableName, final HTableDescriptor htd)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preModifyTable(ctx, tableName, htd);
       }
     });
   }
 
   public void postModifyTable(final TableName tableName, final HTableDescriptor htd)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postModifyTable(ctx, tableName, htd);
       }
     });
   }
 
   public void preModifyTableHandler(final TableName tableName, final HTableDescriptor htd)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preModifyTableHandler(ctx, tableName, htd);
       }
     });
   }
 
   public void postModifyTableHandler(final TableName tableName, final HTableDescriptor htd)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postModifyTableHandler(ctx, tableName, htd);
       }
     });
   }
 
   public boolean preAddColumn(final TableName tableName, final HColumnDescriptor column)
       throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preAddColumn(ctx, tableName, column);
       }
     });
   }
 
   public void postAddColumn(final TableName tableName, final HColumnDescriptor column)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postAddColumn(ctx, tableName, column);
       }
     });
   }
 
   public boolean preAddColumnHandler(final TableName tableName, final HColumnDescriptor column)
       throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preAddColumnHandler(ctx, tableName, column);
       }
     });
   }
 
   public void postAddColumnHandler(final TableName tableName, final HColumnDescriptor column)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postAddColumnHandler(ctx, tableName, column);
       }
     });
   }
 
   public boolean preModifyColumn(final TableName tableName, final HColumnDescriptor descriptor)
       throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preModifyColumn(ctx, tableName, descriptor);
       }
     });
   }
 
   public void postModifyColumn(final TableName tableName, final HColumnDescriptor descriptor)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postModifyColumn(ctx, tableName, descriptor);
       }
     });
   }
 
   public boolean preModifyColumnHandler(final TableName tableName,
       final HColumnDescriptor descriptor) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preModifyColumnHandler(ctx, tableName, descriptor);
       }
     });
   }
 
   public void postModifyColumnHandler(final TableName tableName,
       final HColumnDescriptor descriptor) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postModifyColumnHandler(ctx, tableName, descriptor);
       }
     });
   }
 
   public boolean preDeleteColumn(final TableName tableName, final byte [] c) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preDeleteColumn(ctx, tableName, c);
       }
     });
   }
 
   public void postDeleteColumn(final TableName tableName, final byte [] c) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postDeleteColumn(ctx, tableName, c);
       }
     });
   }
 
   public boolean preDeleteColumnHandler(final TableName tableName, final byte[] c)
       throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preDeleteColumnHandler(ctx, tableName, c);
       }
     });
   }
 
   public void postDeleteColumnHandler(final TableName tableName, final byte[] c)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postDeleteColumnHandler(ctx, tableName, c);
       }
     });
   }
 
   public void preEnableTable(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preEnableTable(ctx, tableName);
       }
     });
   }
 
   public void postEnableTable(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postEnableTable(ctx, tableName);
       }
     });
   }
 
   public void preEnableTableHandler(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preEnableTableHandler(ctx, tableName);
       }
     });
   }
 
   public void postEnableTableHandler(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postEnableTableHandler(ctx, tableName);
       }
     });
   }
 
   public void preDisableTable(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preDisableTable(ctx, tableName);
       }
     });
   }
 
   public void postDisableTable(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postDisableTable(ctx, tableName);
       }
     });
   }
 
   public void preDisableTableHandler(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preDisableTableHandler(ctx, tableName);
       }
     });
   }
 
   public void postDisableTableHandler(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postDisableTableHandler(ctx, tableName);
       }
     });
   }
 
   public boolean preAbortProcedure(
       final ProcedureExecutor<MasterProcedureEnv> procEnv,
       final long procId) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preAbortProcedure(ctx, procEnv, procId);
       }
     });
   }
 
   public void postAbortProcedure() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postAbortProcedure(ctx);
       }
     });
   }
 
   public boolean preListProcedures() throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preListProcedures(ctx);
       }
     });
   }
 
   public void postListProcedures(final List<ProcedureInfo> procInfoList) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postListProcedures(ctx, procInfoList);
       }
     });
   }
 
   public boolean preMove(final HRegionInfo region, final ServerName srcServer,
       final ServerName destServer) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preMove(ctx, region, srcServer, destServer);
       }
     });
   }
 
   public void postMove(final HRegionInfo region, final ServerName srcServer,
       final ServerName destServer) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postMove(ctx, region, srcServer, destServer);
       }
     });
   }
 
   public boolean preAssign(final HRegionInfo regionInfo) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preAssign(ctx, regionInfo);
       }
     });
   }
 
   public void postAssign(final HRegionInfo regionInfo) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postAssign(ctx, regionInfo);
       }
     });
   }
 
   public boolean preUnassign(final HRegionInfo regionInfo, final boolean force)
       throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preUnassign(ctx, regionInfo, force);
       }
     });
   }
 
   public void postUnassign(final HRegionInfo regionInfo, final boolean force) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postUnassign(ctx, regionInfo, force);
       }
     });
   }
 
   public void preRegionOffline(final HRegionInfo regionInfo) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preRegionOffline(ctx, regionInfo);
       }
     });
   }
 
   public void postRegionOffline(final HRegionInfo regionInfo) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postRegionOffline(ctx, regionInfo);
       }
     });
   }
 
   public void preDispatchMerge(final HRegionInfo regionInfoA, final HRegionInfo regionInfoB)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preDispatchMerge(ctx, regionInfoA, regionInfoB);
       }
     });
   }
 
   public void postDispatchMerge(final HRegionInfo regionInfoA, final HRegionInfo regionInfoB)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postDispatchMerge(ctx, regionInfoA, regionInfoB);
       }
     });
   }
 
   public boolean preBalance() throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preBalance(ctx);
       }
     });
   }
 
   public void postBalance(final List<RegionPlan> plans) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postBalance(ctx, plans);
       }
     });
   }
 
   public boolean preSetSplitOrMergeEnabled(final boolean newValue,
       final Admin.MasterSwitchType switchType) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null :
       new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSetSplitOrMergeEnabled(ctx, newValue, switchType);
       }
     });
   }
 
   public void postSetSplitOrMergeEnabled(final boolean newValue,
       final Admin.MasterSwitchType switchType) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postSetSplitOrMergeEnabled(ctx, newValue, switchType);
       }
     });
   }
 
   public boolean preBalanceSwitch(final boolean b) throws IOException {
     return execOperationWithResult(b, coprocessors.isEmpty() ? null :
         new CoprocessorOperationWithResult<Boolean>() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         setResult(oserver.preBalanceSwitch(ctx, getResult()));
       }
     });
   }
 
   public void postBalanceSwitch(final boolean oldValue, final boolean newValue)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postBalanceSwitch(ctx, oldValue, newValue);
       }
     });
   }
 
   public void preShutdown() throws IOException {
     // While stopping the cluster all coprocessors method should be executed first then the
     // coprocessor should be cleaned up.
     execShutdown(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preShutdown(ctx);
       }
       @Override
       public void postEnvCall(MasterEnvironment env) {
         // invoke coprocessor stop method
         shutdown(env);
       }
     });
   }
 
   public void preStopMaster() throws IOException {
     // While stopping master all coprocessors method should be executed first then the coprocessor
     // environment should be cleaned up.
     execShutdown(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preStopMaster(ctx);
       }
       @Override
       public void postEnvCall(MasterEnvironment env) {
         // invoke coprocessor stop method
         shutdown(env);
       }
     });
   }
 
   public void preMasterInitialization() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preMasterInitialization(ctx);
       }
     });
   }
 
   public void postStartMaster() throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postStartMaster(ctx);
       }
     });
   }
 
   public void preSnapshot(final SnapshotDescription snapshot,
       final HTableDescriptor hTableDescriptor) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSnapshot(ctx, snapshot, hTableDescriptor);
       }
     });
   }
 
   public void postSnapshot(final SnapshotDescription snapshot,
       final HTableDescriptor hTableDescriptor) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postSnapshot(ctx, snapshot, hTableDescriptor);
       }
     });
   }
 
   public void preListSnapshot(final SnapshotDescription snapshot) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver observer, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         observer.preListSnapshot(ctx, snapshot);
       }
     });
   }
 
   public void postListSnapshot(final SnapshotDescription snapshot) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver observer, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         observer.postListSnapshot(ctx, snapshot);
       }
     });
   }
   
   public void preCloneSnapshot(final SnapshotDescription snapshot,
       final HTableDescriptor hTableDescriptor) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preCloneSnapshot(ctx, snapshot, hTableDescriptor);
       }
     });
   }
 
   public void postCloneSnapshot(final SnapshotDescription snapshot,
       final HTableDescriptor hTableDescriptor) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postCloneSnapshot(ctx, snapshot, hTableDescriptor);
       }
     });
   }
 
   public void preRestoreSnapshot(final SnapshotDescription snapshot,
       final HTableDescriptor hTableDescriptor) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preRestoreSnapshot(ctx, snapshot, hTableDescriptor);
       }
     });
   }
 
   public void postRestoreSnapshot(final SnapshotDescription snapshot,
       final HTableDescriptor hTableDescriptor) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postRestoreSnapshot(ctx, snapshot, hTableDescriptor);
       }
     });
   }
 
   public void preDeleteSnapshot(final SnapshotDescription snapshot) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preDeleteSnapshot(ctx, snapshot);
       }
     });
   }
 
   public void postDeleteSnapshot(final SnapshotDescription snapshot) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postDeleteSnapshot(ctx, snapshot);
       }
     });
   }
 
   @Deprecated
   public boolean preGetTableDescriptors(final List<TableName> tableNamesList,
     final List<HTableDescriptor> descriptors) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preGetTableDescriptors(ctx, tableNamesList, descriptors);
       }
     });
   }
 
   @Deprecated
   public void postGetTableDescriptors(final List<HTableDescriptor> descriptors)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postGetTableDescriptors(ctx, descriptors);
       }
     });
   }
 
   public boolean preGetTableDescriptors(final List<TableName> tableNamesList,
       final List<HTableDescriptor> descriptors, final String regex) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preGetTableDescriptors(ctx, tableNamesList, descriptors, regex);
       }
     });
   }
 
   public void postGetTableDescriptors(final List<TableName> tableNamesList,
       final List<HTableDescriptor> descriptors, final String regex) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postGetTableDescriptors(ctx, tableNamesList, descriptors, regex);
       }
     });
   }
 
   public boolean preGetTableNames(final List<HTableDescriptor> descriptors,
       final String regex) throws IOException {
     return execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preGetTableNames(ctx, descriptors, regex);
       }
     });
   }
 
   public void postGetTableNames(final List<HTableDescriptor> descriptors,
       final String regex) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postGetTableNames(ctx, descriptors, regex);
       }
     });
   }
 
   public void preTableFlush(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preTableFlush(ctx, tableName);
       }
     });
   }
 
   public void postTableFlush(final TableName tableName) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postTableFlush(ctx, tableName);
       }
     });
   }
   
   public void preSetUserQuota(final String user, final Quotas quotas) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSetUserQuota(ctx, user, quotas);
       }
     });
   }
 
   public void postSetUserQuota(final String user, final Quotas quotas) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postSetUserQuota(ctx, user, quotas);
       }
     });
   }
 
   public void preSetUserQuota(final String user, final TableName table, final Quotas quotas)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSetUserQuota(ctx, user, table, quotas);
       }
     });
   }
 
   public void postSetUserQuota(final String user, final TableName table, final Quotas quotas)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postSetUserQuota(ctx, user, table, quotas);
       }
     });
   }
 
   public void preSetUserQuota(final String user, final String namespace, final Quotas quotas)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSetUserQuota(ctx, user, namespace, quotas);
       }
     });
   }
 
   public void postSetUserQuota(final String user, final String namespace, final Quotas quotas)
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postSetUserQuota(ctx, user, namespace, quotas);
       }
     });
   }
 
   public void preSetTableQuota(final TableName table, final Quotas quotas) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSetTableQuota(ctx, table, quotas);
       }
     });
   }
 
   public void postSetTableQuota(final TableName table, final Quotas quotas) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postSetTableQuota(ctx, table, quotas);
       }
     });
   }
 
   public void preSetNamespaceQuota(final String namespace, final Quotas quotas) throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.preSetNamespaceQuota(ctx, namespace, quotas);
       }
     });
   }
 
   public void postSetNamespaceQuota(final String namespace, final Quotas quotas) 
       throws IOException {
     execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
       @Override
       public void call(MasterObserver oserver, ObserverContext<MasterCoprocessorEnvironment> ctx)
           throws IOException {
         oserver.postSetNamespaceQuota(ctx, namespace, quotas);
       }
     });
   }
 
   private static abstract class CoprocessorOperation
       extends ObserverContext<MasterCoprocessorEnvironment> {
     public CoprocessorOperation() {
     }
 
     public abstract void call(MasterObserver oserver,
         ObserverContext<MasterCoprocessorEnvironment> ctx) throws IOException;
 
     public void postEnvCall(MasterEnvironment env) {
     }
   }
 
   private static abstract class CoprocessorOperationWithResult<T> extends CoprocessorOperation {
     private T result = null;
     public void setResult(final T result) { this.result = result; }
     public T getResult() { return this.result; }
   }
 
   private <T> T execOperationWithResult(final T defaultValue,
       final CoprocessorOperationWithResult<T> ctx) throws IOException {
     if (ctx == null) return defaultValue;
     ctx.setResult(defaultValue);
     execOperation(ctx);
     return ctx.getResult();
   }
 
   private boolean execOperation(final CoprocessorOperation ctx) throws IOException {
     if (ctx == null) return false;
     boolean bypass = false;
     List<MasterEnvironment> envs = coprocessors.get();
     for (int i = 0; i < envs.size(); i++) {
       MasterEnvironment env = envs.get(i);
       if (env.getInstance() instanceof MasterObserver) {
         ctx.prepare(env);
         Thread currentThread = Thread.currentThread();
         ClassLoader cl = currentThread.getContextClassLoader();
         try {
           currentThread.setContextClassLoader(env.getClassLoader());
           ctx.call((MasterObserver)env.getInstance(), ctx);
         } catch (Throwable e) {
           handleCoprocessorThrowable(env, e);
         } finally {
           currentThread.setContextClassLoader(cl);
         }
         bypass |= ctx.shouldBypass();
         if (ctx.shouldComplete()) {
           break;
         }
       }
       ctx.postEnvCall(env);
     }
     return bypass;
   }
 
   /**
    * Master coprocessor classes can be configured in any order, based on that priority is set and
    * chained in a sorted order. For preStopMaster()/preShutdown(), coprocessor methods are invoked
    * in call() and environment is shutdown in postEnvCall(). <br>
    * Need to execute all coprocessor methods first then postEnvCall(), otherwise some coprocessors
    * may remain shutdown if any exception occurs during next coprocessor execution which prevent
    * Master stop or cluster shutdown. (Refer:
    * <a href="https://issues.apache.org/jira/browse/HBASE-16663">HBASE-16663</a>
    * @param ctx CoprocessorOperation
    * @return true if bypaas coprocessor execution, false if not.
    * @throws IOException
    */
   private boolean execShutdown(final CoprocessorOperation ctx) throws IOException {
     if (ctx == null) return false;
     boolean bypass = false;
     List<MasterEnvironment> envs = coprocessors.get();
     int envsSize = envs.size();
     // Iterate the coprocessors and execute CoprocessorOperation's call()
     for (int i = 0; i < envsSize; i++) {
       MasterEnvironment env = envs.get(i);
       if (env.getInstance() instanceof MasterObserver) {
         ctx.prepare(env);
         Thread currentThread = Thread.currentThread();
         ClassLoader cl = currentThread.getContextClassLoader();
         try {
           currentThread.setContextClassLoader(env.getClassLoader());
           ctx.call((MasterObserver) env.getInstance(), ctx);
         } catch (Throwable e) {
           handleCoprocessorThrowable(env, e);
         } finally {
           currentThread.setContextClassLoader(cl);
         }
         bypass |= ctx.shouldBypass();
         if (ctx.shouldComplete()) {
           break;
         }
       }
     }
 
     // Iterate the coprocessors and execute CoprocessorOperation's postEnvCall()
     for (int i = 0; i < envsSize; i++) {
       MasterEnvironment env = envs.get(i);
       ctx.postEnvCall(env);
     }
     return bypass;
   }
 
 }