org.apache.hadoop.hdfs.server.protocol.JournalProtocol Maven / Gradle / Ivy
/**
* 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.security.KerberosInfo;
/**
* Protocol used to journal edits to a remote node. Currently,
* this is used to publish edits from the NameNode to a BackupNode.
*/
@KerberosInfo(
serverPrincipal = DFSConfigKeys.DFS_NAMENODE_KERBEROS_PRINCIPAL_KEY,
clientPrincipal = DFSConfigKeys.DFS_NAMENODE_KERBEROS_PRINCIPAL_KEY)
@InterfaceAudience.Private
public interface JournalProtocol {
/**
*
* This class is used by both the Namenode (client) and BackupNode (server)
* to insulate from the protocol serialization.
*
* If you are adding/changing DN's interface then you need to
* change both this class and ALSO related protocol buffer
* wire protocol definition in JournalProtocol.proto.
*
* For more details on protocol buffer wire protocol, please see
* .../org/apache/hadoop/hdfs/protocolPB/overview.html
*/
public static final long versionID = 1L;
/**
* Journal edit records.
* This message is sent by the active name-node to the backup node
* via {@code EditLogBackupOutputStream} in order to synchronize meta-data
* changes with the backup namespace image.
*
* @param journalInfo journal information
* @param epoch marks beginning a new journal writer
* @param firstTxnId the first transaction of this batch
* @param numTxns number of transactions
* @param records byte array containing serialized journal records
* @throws FencedException if the resource has been fenced
*/
public void journal(JournalInfo journalInfo,
long epoch,
long firstTxnId,
int numTxns,
byte[] records) throws IOException;
/**
* Notify the BackupNode that the NameNode has rolled its edit logs
* and is now writing a new log segment.
* @param journalInfo journal information
* @param epoch marks beginning a new journal writer
* @param txid the first txid in the new log
* @throws FencedException if the resource has been fenced
*/
public void startLogSegment(JournalInfo journalInfo, long epoch,
long txid) throws IOException;
/**
* Request to fence any other journal writers.
* Older writers with at previous epoch will be fenced and can no longer
* perform journal operations.
*
* @param journalInfo journal information
* @param epoch marks beginning a new journal writer
* @param fencerInfo info about fencer for debugging purposes
* @throws FencedException if the resource has been fenced
*/
public FenceResponse fence(JournalInfo journalInfo, long epoch,
String fencerInfo) throws IOException;
}