/**
* Copyright 2009 The Apache Software Foundation
*
* 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.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.TableNotFoundException;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.Writables;
/**
* Scanner class that contains the <code>.META.</code> table scanning logic
* and uses a Retryable scanner. Provided visitors will be called
* for each row.
*
* Although public visibility, this is not a public-facing API and may evolve in
* minor releases.
*/
public class MetaScanner {
private static final Log LOG = LogFactory.getLog(MetaScanner.class);
/**
* Scans the meta table and calls a visitor on each RowResult and uses a empty
* start row value as table name.
*
* @param configuration conf
* @param visitor A custom visitor
* @throws IOException e
*/
public static void metaScan(Configuration configuration,
MetaScannerVisitor visitor)
throws IOException {
metaScan(configuration, visitor, null);
}
/**
* Scans the meta table and calls a visitor on each RowResult. Uses a table
* name to locate meta regions.
*
* @param configuration config
* @param visitor visitor object
* @param userTableName User table name in meta table to start scan at. Pass
* null if not interested in a particular table.
* @throws IOException e
*/
public static void metaScan(Configuration configuration,
MetaScannerVisitor visitor, byte [] userTableName)
throws IOException {
metaScan(configuration, visitor, userTableName, null, Integer.MAX_VALUE);
}
/**
* Scans the meta table and calls a visitor on each RowResult. Uses a table
* name and a row name to locate meta regions. And it only scans at most
* <code>rowLimit</code> of rows.
*
* @param configuration HBase configuration.
* @param visitor Visitor object.
* @param userTableName User table name in meta table to start scan at. Pass
* null if not interested in a particular table.
* @param row Name of the row at the user table. The scan will start from
* the region row where the row resides.
* @param rowLimit Max of processed rows. If it is less than 0, it
* will be set to default value <code>Integer.MAX_VALUE</code>.
* @throws IOException e
*/
public static void metaScan(Configuration configuration,
MetaScannerVisitor visitor, byte [] userTableName, byte[] row,
int rowLimit)
throws IOException {
metaScan(configuration, visitor, userTableName, row, rowLimit,
HConstants.META_TABLE_NAME);
}
/**
* Scans the meta table and calls a visitor on each RowResult. Uses a table
* name and a row name to locate meta regions. And it only scans at most
* <code>rowLimit</code> of rows.
*
* @param configuration HBase configuration.
* @param visitor Visitor object.
* @param tableName User table name in meta table to start scan at. Pass
* null if not interested in a particular table.
* @param row Name of the row at the user table. The scan will start from
* the region row where the row resides.
* @param rowLimit Max of processed rows. If it is less than 0, it
* will be set to default value <code>Integer.MAX_VALUE</code>.
* @param metaTableName Meta table to scan, root or meta.
* @throws IOException e
*/
public static void metaScan(Configuration configuration,
MetaScannerVisitor visitor, byte [] tableName, byte[] row,
int rowLimit, final byte [] metaTableName)
throws IOException {
int rowUpperLimit = rowLimit > 0 ? rowLimit: Integer.MAX_VALUE;
HConnection connection = HConnectionManager.getConnection(configuration);
// if row is not null, we want to use the startKey of the row's region as
// the startRow for the meta scan.
byte[] startRow;
if (row != null) {
// Scan starting at a particular row in a particular table
assert tableName != null;
byte[] searchRow =
HRegionInfo.createRegionName(tableName, row, HConstants.NINES,
false);
HTable metaTable = new HTable(configuration, HConstants.META_TABLE_NAME);
Result startRowResult = metaTable.getRowOrBefore(searchRow,
HConstants.CATALOG_FAMILY);
if (startRowResult == null) {
throw new TableNotFoundException("Cannot find row in .META. for table: "
+ Bytes.toString(tableName) + ", row=" + Bytes.toString(searchRow));
}
byte[] value = startRowResult.getValue(HConstants.CATALOG_FAMILY,
HConstants.REGIONINFO_QUALIFIER);
if (value == null || value.length == 0) {
throw new IOException("HRegionInfo was null or empty in Meta for " +
Bytes.toString(tableName) + ", row=" + Bytes.toString(searchRow));
}
HRegionInfo regionInfo = Writables.getHRegionInfo(value);
byte[] rowBefore = regionInfo.getStartKey();
startRow = HRegionInfo.createRegionName(tableName, rowBefore,
HConstants.ZEROES, false);
} else if (tableName == null || tableName.length == 0) {
// Full META scan
startRow = HConstants.EMPTY_START_ROW;
} else {
// Scan META for an entire table
startRow = HRegionInfo.createRegionName(
tableName, HConstants.EMPTY_START_ROW, HConstants.ZEROES, false);
}
// Scan over each meta region
ScannerCallable callable;
int rows = Math.min(rowLimit,
configuration.getInt("hbase.meta.scanner.caching", 100));
do {
final Scan scan = new Scan(startRow).addFamily(HConstants.CATALOG_FAMILY);
if (LOG.isDebugEnabled()) {
LOG.debug("Scanning " + Bytes.toString(metaTableName) +
" starting at row=" + Bytes.toString(startRow) + " for max=" +
rowUpperLimit + " rows");
}
callable = new ScannerCallable(connection, metaTableName, scan);
// Open scanner
connection.getRegionServerWithRetries(callable);
int processedRows = 0;
try {
callable.setCaching(rows);
done: do {
if (processedRows >= rowUpperLimit) {
break;
}
//we have all the rows here
Result [] rrs = connection.getRegionServerWithRetries(callable);
if (rrs == null || rrs.length == 0 || rrs[0].size() == 0) {
break; //exit completely
}
for (Result rr : rrs) {
if (processedRows >= rowUpperLimit) {
break done;
}
if (!visitor.processRow(rr))
break done; //exit completely
processedRows++;
}
//here, we didn't break anywhere. Check if we have more rows
} while(true);
// Advance the startRow to the end key of the current region
startRow = callable.getHRegionInfo().getEndKey();
} finally {
// Close scanner
callable.setClose();
connection.getRegionServerWithRetries(callable);
}
} while (Bytes.compareTo(startRow, HConstants.LAST_ROW) != 0);
}
/**
* Lists all of the regions currently in META.
* @param conf
* @return List of all user-space regions.
* @throws IOException
*/
public static List<HRegionInfo> listAllRegions(Configuration conf)
throws IOException {
return listAllRegions(conf, true);
}
/**
* Lists all of the regions currently in META.
* @param conf
* @param offlined True if we are to include offlined regions, false and we'll
* leave out offlined regions from returned list.
* @return List of all user-space regions.
* @throws IOException
*/
public static List<HRegionInfo> listAllRegions(Configuration conf, final boolean offlined)
throws IOException {
final List<HRegionInfo> regions = new ArrayList<HRegionInfo>();
MetaScannerVisitor visitor =
new MetaScannerVisitor() {
@Override
public boolean processRow(Result result) throws IOException {
if (result == null || result.isEmpty()) {
return true;
}
byte [] bytes = result.getValue(HConstants.CATALOG_FAMILY,
HConstants.REGIONINFO_QUALIFIER);
if (bytes == null) {
LOG.warn("Null REGIONINFO_QUALIFIER: " + result);
return true;
}
HRegionInfo regionInfo = Writables.getHRegionInfo(bytes);
// If region offline AND we are not to include offlined regions, return.
if (regionInfo.isOffline() && !offlined) return true;
regions.add(regionInfo);
return true;
}
};
metaScan(conf, visitor);
return regions;
}
/**
* Visitor class called to process each row of the .META. table
*/
public interface MetaScannerVisitor {
/**
* Visitor method that accepts a RowResult and the meta region location.
* Implementations can return false to stop the region's loop if it becomes
* unnecessary for some reason.
*
* @param rowResult result
* @return A boolean to know if it should continue to loop in the region
* @throws IOException e
*/
public boolean processRow(Result rowResult) throws IOException;
}
}