MasterCoprocessorHost.java example

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pbase-master
/*
 *
 * 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 org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.*;
import org.apache.hadoop.hbase.coprocessor.*;
import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.SnapshotDescription;

import java.io.IOException;
import java.util.List;

/**
 * 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> {

  /**
   * 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;

  MasterCoprocessorHost(final MasterServices services, final Configuration conf) {
    super(services);
    this.conf = conf;
    this.masterServices = services;
    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 (Class<?> c : implClass.getInterfaces()) {
      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 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 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 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 {
    execOperation(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 {
    execOperation(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 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);
      }
    });
  }

  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;
    for (MasterEnvironment env: coprocessors) {
      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;
  }
}