| /** |
| * 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_USER_NAME_KEY, |
| clientPrincipal = DFSConfigKeys.DFS_NAMENODE_USER_NAME_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; |
| } |