/**
* 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.server.protocol;
import java.io.IOException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
import org.apache.hadoop.hdfs.security.token.block.ExportedBlockKeys;
import org.apache.hadoop.hdfs.server.namenode.CheckpointSignature;
import org.apache.hadoop.io.retry.AtMostOnce;
import org.apache.hadoop.io.retry.Idempotent;
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
*****************************************************************************/
@KerberosInfo(
serverPrincipal = DFSConfigKeys.DFS_NAMENODE_USER_NAME_KEY)
@InterfaceAudience.Private
public interface NamenodeProtocol {
/**
* Until version 6L, this class served as both
* the client interface to the NN AND the RPC protocol used to
* communicate with the NN.
*
* This class is used by both the DFSClient and the
* NN server side to insulate from the protocol serialization.
*
* If you are adding/changing NN's interface then you need to
* change both this class and ALSO related protocol buffer
* wire protocol definition in NamenodeProtocol.proto.
*
* For more details on protocol buffer wire protocol, please see
* .../org/apache/hadoop/hdfs/protocolPB/overview.html
*
* 6: Switch to txid-based file naming for image and edits
*/
public static final long versionID = 6L;
// Error codes passed by errorReport().
final static int NOTIFY = 0;
final static int FATAL = 1;
public final static int ACT_UNKNOWN = 0; // unknown action
public final static int ACT_SHUTDOWN = 50; // shutdown node
public final static int ACT_CHECKPOINT = 51; // do checkpoint
/**
* Get a list of blocks belonging to <code>datanode</code>
* whose total size equals <code>size</code>.
*
* @see org.apache.hadoop.hdfs.server.balancer.Balancer
* @param datanode a data node
* @param size requested size
* @return a list of blocks & their locations
* @throws IOException if size is less than or equal to 0 or
datanode does not exist
*/
@Idempotent
public BlocksWithLocations getBlocks(DatanodeInfo datanode, long size)
throws IOException;
/**
* Get the current block keys
*
* @return ExportedBlockKeys containing current block keys
* @throws IOException
*/
@Idempotent
public ExportedBlockKeys getBlockKeys() throws IOException;
/**
* @return The most recent transaction ID that has been synced to
* persistent storage, or applied from persistent storage in the
* case of a non-active node.
* @throws IOException
*/
@Idempotent
public long getTransactionID() throws IOException;
/**
* Get the transaction ID of the most recent checkpoint.
*/
@Idempotent
public long getMostRecentCheckpointTxId() throws IOException;
/**
* Closes the current edit log and opens a new one. The
* call fails if the file system is in SafeMode.
* @throws IOException
* @return a unique token to identify this transaction.
*/
@Idempotent
public CheckpointSignature rollEditLog() throws IOException;
/**
* Request name-node version and storage information.
*
* @return {@link NamespaceInfo} identifying versions and storage information
* of the name-node
* @throws IOException
*/
@Idempotent
public NamespaceInfo versionRequest() throws IOException;
/**
* Report to the active name-node an error occurred on a subordinate node.
* Depending on the error code the active node may decide to unregister the
* reporting node.
*
* @param registration requesting node.
* @param errorCode indicates the error
* @param msg free text description of the error
* @throws IOException
*/
@Idempotent
public void errorReport(NamenodeRegistration registration,
int errorCode,
String msg) throws IOException;
/**
* Register a subordinate name-node like backup node.
*
* @return {@link NamenodeRegistration} of the node,
* which this node has just registered with.
*/
@Idempotent
public NamenodeRegistration registerSubordinateNamenode(
NamenodeRegistration registration) throws IOException;
/**
* A request to the active name-node to start a checkpoint.
* The name-node should decide whether to admit it or reject.
* The name-node also decides what should be done with the backup node
* image before and after the checkpoint.
*
* @see CheckpointCommand
* @see NamenodeCommand
* @see #ACT_SHUTDOWN
*
* @param registration the requesting node
* @return {@link CheckpointCommand} if checkpoint is allowed.
* @throws IOException
*/
@AtMostOnce
public NamenodeCommand startCheckpoint(NamenodeRegistration registration)
throws IOException;
/**
* A request to the active name-node to finalize
* previously started checkpoint.
*
* @param registration the requesting node
* @param sig {@code CheckpointSignature} which identifies the checkpoint.
* @throws IOException
*/
@AtMostOnce
public void endCheckpoint(NamenodeRegistration registration,
CheckpointSignature sig) throws IOException;
/**
* Return a structure containing details about all edit logs
* available to be fetched from the NameNode.
* @param sinceTxId return only logs that contain transactions >= sinceTxId
*/
@Idempotent
public RemoteEditLogManifest getEditLogManifest(long sinceTxId)
throws IOException;
}