/**
* 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;
import java.io.IOException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.DFSInputStream;
import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
import org.apache.hadoop.hdfs.protocol.LocatedBlocksWithMetaInfo;
import org.apache.hadoop.hdfs.server.namenode.SnapshotShell;
/**
* A SnapshotClient which allows opening snapshot files for reading
* and listing their LocatedBlocks.
* Note: For all paths, just prepend snapshot id to them. E.g for
* file at /foo in snapshot with id test, put src as test/foo
*/
public class SnapshotClient {
public static final Log LOG = LogFactory.getLog(SnapshotClient.class);
private Configuration conf;
private DFSClient client;
private SnapshotShell shell;
private boolean clientRunning = true;
public SnapshotClient(Configuration conf) throws IOException {
this.conf = conf;
this.client = new DFSClient(conf);
this.shell = new SnapshotShell(conf);
}
public LocatedBlocksWithMetaInfo[] getLocatedBlocks(String snapshotId,
String src) throws IOException {
return shell.getSnapshotNode().getLocatedBlocks(snapshotId, src);
}
public DFSInputStream open(String snapshotId, String src) throws IOException {
LocatedBlocksWithMetaInfo blocks[] = getLocatedBlocks(snapshotId, src);
// Not strictly correct. block.length = 1 could mean directory with
// one file. Might want to add a file specific API.
if (blocks == null || blocks.length != 1) {
throw new IOException("File at " + src + " doesn't exist in snapshot");
}
return client.open(blocks[0]);
}
private void checkOpen() throws IOException {
if (!clientRunning) {
throw new IOException("SnapshotClient not running");
}
}
public synchronized void close() throws IOException {
clientRunning = false;
client.close();
shell.close();
}
}