org.apache.hadoop.hdfs.tools.offlineEditsViewer.OfflineEditsVisitor 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.tools.offlineEditsViewer;
import java.io.IOException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp;
/**
* An implementation of OfflineEditsVisitor can traverse the structure of an
* Hadoop edits log and respond to each of the structures within the file.
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
abstract public interface OfflineEditsVisitor {
/**
* Begin visiting the edits log structure. Opportunity to perform
* any initialization necessary for the implementing visitor.
*
* @param version Edit log version
*/
abstract void start(int version) throws IOException;
/**
* Finish visiting the edits log structure. Opportunity to perform any
* clean up necessary for the implementing visitor.
*
* @param error If the visitor was closed because of an
* unrecoverable error in the input stream, this
* is the exception.
*/
abstract void close(Throwable error) throws IOException;
/**
* Begin visiting an element that encloses another element, such as
* the beginning of the list of blocks that comprise a file.
*
* @param op Token being visited
*/
abstract void visitOp(FSEditLogOp op)
throws IOException;
}