/**
* 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.hbase.client;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.UUID;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.HTableDescriptor;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.snapshot.RestoreSnapshotHelper;
import org.apache.hadoop.hbase.util.FSUtils;
/**
* A Scanner which performs a scan over snapshot files. Using this class requires copying the
* snapshot to a temporary empty directory, which will copy the snapshot reference files into that
* directory. Actual data files are not copied.
*
* <p>
* This also allows one to run the scan from an
* online or offline hbase cluster. The snapshot files can be exported by using the
* {@link org.apache.hadoop.hbase.snapshot.ExportSnapshot} tool,
* to a pure-hdfs cluster, and this scanner can be used to
* run the scan directly over the snapshot files. The snapshot should not be deleted while there
* are open scanners reading from snapshot files.
*
* <p>
* An internal RegionScanner is used to execute the {@link Scan} obtained
* from the user for each region in the snapshot.
* <p>
* HBase owns all the data and snapshot files on the filesystem. Only the HBase user can read from
* snapshot files and data files. HBase also enforces security because all the requests are handled
* by the server layer, and the user cannot read from the data files directly. To read from snapshot
* files directly from the file system, the user who is running the MR job must have sufficient
* permissions to access snapshot and reference files. This means that to run mapreduce over
* snapshot files, the job has to be run as the HBase user or the user must have group or other
* priviledges in the filesystem (See HBASE-8369). Note that, given other users access to read from
* snapshot/data files will completely circumvent the access control enforced by HBase.
* @see org.apache.hadoop.hbase.mapreduce.TableSnapshotInputFormat
*/
@InterfaceAudience.Public
public class TableSnapshotScanner extends AbstractClientScanner {
private static final Log LOG = LogFactory.getLog(TableSnapshotScanner.class);
private Configuration conf;
private String snapshotName;
private FileSystem fs;
private Path rootDir;
private Path restoreDir;
private Scan scan;
private ArrayList<HRegionInfo> regions;
private HTableDescriptor htd;
private ClientSideRegionScanner currentRegionScanner = null;
private int currentRegion = -1;
/**
* Creates a TableSnapshotScanner.
* @param conf the configuration
* @param restoreDir a temporary directory to copy the snapshot files into. Current user should
* have write permissions to this directory, and this should not be a subdirectory of rootdir.
* The scanner deletes the contents of the directory once the scanner is closed.
* @param snapshotName the name of the snapshot to read from
* @param scan a Scan representing scan parameters
* @throws IOException in case of error
*/
public TableSnapshotScanner(Configuration conf, Path restoreDir,
String snapshotName, Scan scan) throws IOException {
this(conf, FSUtils.getRootDir(conf), restoreDir, snapshotName, scan);
}
/**
* Creates a TableSnapshotScanner.
* @param conf the configuration
* @param rootDir root directory for HBase.
* @param restoreDir a temporary directory to copy the snapshot files into. Current user should
* have write permissions to this directory, and this should not be a subdirectory of rootdir.
* The scanner deletes the contents of the directory once the scanner is closed.
* @param snapshotName the name of the snapshot to read from
* @param scan a Scan representing scan parameters
* @throws IOException in case of error
*/
public TableSnapshotScanner(Configuration conf, Path rootDir,
Path restoreDir, String snapshotName, Scan scan) throws IOException {
this.conf = conf;
this.snapshotName = snapshotName;
this.rootDir = rootDir;
// restoreDir will be deleted in close(), use a unique sub directory
this.restoreDir = new Path(restoreDir, UUID.randomUUID().toString());
this.scan = scan;
this.fs = rootDir.getFileSystem(conf);
init();
}
private void init() throws IOException {
final RestoreSnapshotHelper.RestoreMetaChanges meta =
RestoreSnapshotHelper.copySnapshotForScanner(
conf, fs, rootDir, restoreDir, snapshotName);
final List<HRegionInfo> restoredRegions = meta.getRegionsToAdd();
htd = meta.getTableDescriptor();
regions = new ArrayList<>(restoredRegions.size());
for (HRegionInfo hri: restoredRegions) {
if (CellUtil.overlappingKeys(scan.getStartRow(), scan.getStopRow(),
hri.getStartKey(), hri.getEndKey())) {
regions.add(hri);
}
}
// sort for regions according to startKey.
Collections.sort(regions);
initScanMetrics(scan);
}
@Override
public Result next() throws IOException {
Result result = null;
while (true) {
if (currentRegionScanner == null) {
currentRegion++;
if (currentRegion >= regions.size()) {
return null;
}
HRegionInfo hri = regions.get(currentRegion);
currentRegionScanner = new ClientSideRegionScanner(conf, fs,
restoreDir, htd, hri, scan, scanMetrics);
if (this.scanMetrics != null) {
this.scanMetrics.countOfRegions.incrementAndGet();
}
}
try {
result = currentRegionScanner.next();
if (result != null) {
return result;
}
} finally {
if (result == null) {
currentRegionScanner.close();
currentRegionScanner = null;
}
}
}
}
@Override
public void close() {
if (currentRegionScanner != null) {
currentRegionScanner.close();
}
try {
fs.delete(this.restoreDir, true);
} catch (IOException ex) {
LOG.warn("Could not delete restore directory for the snapshot:" + ex);
}
}
@Override
public boolean renewLease() {
throw new UnsupportedOperationException();
}
}