/**
 * 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.hdfs.protocolPB;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.protocol.proto.NamenodeProtocolProtos.NamenodeProtocolService;
import org.apache.hadoop.hdfs.protocolR23Compatible.ProtocolSignatureWritable;
import org.apache.hadoop.ipc.ProtocolInfo;
import org.apache.hadoop.ipc.VersionedProtocol;
import org.apache.hadoop.security.KerberosInfo;

/**
 * Protocol that a secondary NameNode uses to communicate with the NameNode.
 * It's used to get part of the name node state
 * 
 * Note: This extends the protocolbuffer service based interface to
 * add annotations required for security.
 */
@KerberosInfo(
    serverPrincipal = DFSConfigKeys.DFS_NAMENODE_USER_NAME_KEY,
    clientPrincipal = DFSConfigKeys.DFS_NAMENODE_USER_NAME_KEY)
@ProtocolInfo(protocolName = 
    "org.apache.hadoop.hdfs.server.protocol.NamenodeProtocol",
    protocolVersion = 1)
@InterfaceAudience.Private
public interface NamenodeProtocolPB extends
    NamenodeProtocolService.BlockingInterface, VersionedProtocol {
  /**
   * This method is defined to get the protocol signature using 
   * the R23 protocol - hence we have added the suffix of 2 the method name
   * to avoid conflict.
   */
  public ProtocolSignatureWritable getProtocolSignature2(String protocol,
      long clientVersion, int clientMethodsHash) throws IOException;
}