/**
* Copyright 2007 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;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Random;
import java.util.TreeMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.client.HConnection;
import org.apache.hadoop.hbase.client.HConnectionManager;
import org.apache.hadoop.hbase.client.HTable;
import org.apache.hadoop.hbase.client.Scanner;
import org.apache.hadoop.hbase.io.BatchUpdate;
import org.apache.hadoop.hbase.io.Cell;
import org.apache.hadoop.hbase.io.RowResult;
import org.apache.hadoop.hbase.regionserver.HLog;
import org.apache.hadoop.hbase.regionserver.HRegion;
import org.apache.hadoop.hbase.regionserver.InternalScanner;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.Writables;
/**
* A non-instantiable class that has a static method capable of compacting
* a table by merging adjacent regions.
*/
class HMerge implements HConstants {
static final Log LOG = LogFactory.getLog(HMerge.class);
static final Random rand = new Random();
/*
* Not instantiable
*/
private HMerge() {
super();
}
/**
* Scans the table and merges two adjacent regions if they are small. This
* only happens when a lot of rows are deleted.
*
* When merging the META region, the HBase instance must be offline.
* When merging a normal table, the HBase instance must be online, but the
* table must be disabled.
*
* @param conf - configuration object for HBase
* @param fs - FileSystem where regions reside
* @param tableName - Table to be compacted
* @throws IOException
*/
public static void merge(HBaseConfiguration conf, FileSystem fs,
final byte [] tableName)
throws IOException {
HConnection connection = HConnectionManager.getConnection(conf);
boolean masterIsRunning = connection.isMasterRunning();
HConnectionManager.deleteConnectionInfo(conf);
if (Bytes.equals(tableName, META_TABLE_NAME)) {
if (masterIsRunning) {
throw new IllegalStateException(
"Can not compact META table if instance is on-line");
}
new OfflineMerger(conf, fs).process();
} else {
if(!masterIsRunning) {
throw new IllegalStateException(
"HBase instance must be running to merge a normal table");
}
new OnlineMerger(conf, fs, tableName).process();
}
}
private static abstract class Merger {
protected final HBaseConfiguration conf;
protected final FileSystem fs;
protected final Path tabledir;
protected final HLog hlog;
private final long maxFilesize;
protected Merger(HBaseConfiguration conf, FileSystem fs,
final byte [] tableName)
throws IOException {
this.conf = conf;
this.fs = fs;
this.maxFilesize =
conf.getLong("hbase.hregion.max.filesize", DEFAULT_MAX_FILE_SIZE);
this.tabledir = new Path(
fs.makeQualified(new Path(conf.get(HBASE_DIR))),
tableName.toString()
);
Path logdir = new Path(tabledir, "merge_" + System.currentTimeMillis() +
HREGION_LOGDIR_NAME);
this.hlog =
new HLog(fs, logdir, conf, null);
}
void process() throws IOException {
try {
for(HRegionInfo[] regionsToMerge = next();
regionsToMerge != null;
regionsToMerge = next()) {
if (!merge(regionsToMerge)) {
return;
}
}
} finally {
try {
hlog.closeAndDelete();
} catch(IOException e) {
LOG.error(e);
}
}
}
protected boolean merge(final HRegionInfo[] info) throws IOException {
if(info.length < 2) {
LOG.info("only one region - nothing to merge");
return false;
}
HRegion currentRegion = null;
long currentSize = 0;
HRegion nextRegion = null;
long nextSize = 0;
for (int i = 0; i < info.length - 1; i++) {
if (currentRegion == null) {
currentRegion =
new HRegion(tabledir, hlog, fs, conf, info[i], null, null);
currentSize = currentRegion.getLargestHStoreSize();
}
nextRegion =
new HRegion(tabledir, hlog, fs, conf, info[i + 1], null, null);
nextSize = nextRegion.getLargestHStoreSize();
if ((currentSize + nextSize) <= (maxFilesize / 2)) {
// We merge two adjacent regions if their total size is less than
// one half of the desired maximum size
LOG.info("merging regions " + currentRegion.getRegionName()
+ " and " + nextRegion.getRegionName());
HRegion mergedRegion =
HRegion.mergeAdjacent(currentRegion, nextRegion);
updateMeta(currentRegion.getRegionName(), nextRegion.getRegionName(),
mergedRegion);
break;
}
LOG.info("not merging regions " + currentRegion.getRegionName()
+ " and " + nextRegion.getRegionName());
currentRegion.close();
currentRegion = nextRegion;
currentSize = nextSize;
}
if(currentRegion != null) {
currentRegion.close();
}
return true;
}
protected abstract HRegionInfo[] next() throws IOException;
protected abstract void updateMeta(final byte [] oldRegion1,
final byte [] oldRegion2, HRegion newRegion)
throws IOException;
}
/** Instantiated to compact a normal user table */
private static class OnlineMerger extends Merger {
private final byte [] tableName;
private final HTable table;
private final Scanner metaScanner;
private HRegionInfo latestRegion;
OnlineMerger(HBaseConfiguration conf, FileSystem fs,
final byte [] tableName)
throws IOException {
super(conf, fs, tableName);
this.tableName = tableName;
this.table = new HTable(conf, META_TABLE_NAME);
this.metaScanner = table.getScanner(COL_REGIONINFO_ARRAY, tableName);
this.latestRegion = null;
}
private HRegionInfo nextRegion() throws IOException {
try {
RowResult results = getMetaRow();
if (results == null) {
return null;
}
Cell regionInfo = results.get(COL_REGIONINFO);
if (regionInfo == null || regionInfo.getValue().length == 0) {
throw new NoSuchElementException("meta region entry missing " +
COL_REGIONINFO);
}
HRegionInfo region = Writables.getHRegionInfo(regionInfo.getValue());
if (!Bytes.equals(region.getTableDesc().getName(), this.tableName)) {
return null;
}
checkOfflined(region);
return region;
} catch (IOException e) {
e = RemoteExceptionHandler.checkIOException(e);
LOG.error("meta scanner error", e);
metaScanner.close();
throw e;
}
}
protected void checkOfflined(final HRegionInfo hri)
throws TableNotDisabledException {
if (!hri.isOffline()) {
throw new TableNotDisabledException("Region " +
hri.getRegionNameAsString() + " is not disabled");
}
}
/*
* Check current row has a HRegionInfo. Skip to next row if HRI is empty.
* @return A Map of the row content else null if we are off the end.
* @throws IOException
*/
private RowResult getMetaRow() throws IOException {
RowResult currentRow = metaScanner.next();
boolean foundResult = false;
while (currentRow != null) {
LOG.info("Row: <" + currentRow.getRow() + ">");
Cell regionInfo = currentRow.get(COL_REGIONINFO);
if (regionInfo == null || regionInfo.getValue().length == 0) {
currentRow = metaScanner.next();
continue;
}
foundResult = true;
break;
}
return foundResult ? currentRow : null;
}
@Override
protected HRegionInfo[] next() throws IOException {
List<HRegionInfo> regions = new ArrayList<HRegionInfo>();
if(latestRegion == null) {
latestRegion = nextRegion();
}
if(latestRegion != null) {
regions.add(latestRegion);
}
latestRegion = nextRegion();
if(latestRegion != null) {
regions.add(latestRegion);
}
return regions.toArray(new HRegionInfo[regions.size()]);
}
@Override
protected void updateMeta(final byte [] oldRegion1,
final byte [] oldRegion2,
HRegion newRegion)
throws IOException {
byte[][] regionsToDelete = {oldRegion1, oldRegion2};
for (int r = 0; r < regionsToDelete.length; r++) {
if(Bytes.equals(regionsToDelete[r], latestRegion.getRegionName())) {
latestRegion = null;
}
table.deleteAll(regionsToDelete[r]);
if(LOG.isDebugEnabled()) {
LOG.debug("updated columns in row: " + regionsToDelete[r]);
}
}
newRegion.getRegionInfo().setOffline(true);
BatchUpdate update = new BatchUpdate(newRegion.getRegionName());
update.put(COL_REGIONINFO,
Writables.getBytes(newRegion.getRegionInfo()));
table.commit(update);
if(LOG.isDebugEnabled()) {
LOG.debug("updated columns in row: "
+ newRegion.getRegionName());
}
}
}
/** Instantiated to compact the meta region */
private static class OfflineMerger extends Merger {
private final List<HRegionInfo> metaRegions = new ArrayList<HRegionInfo>();
private final HRegion root;
OfflineMerger(HBaseConfiguration conf, FileSystem fs)
throws IOException {
super(conf, fs, META_TABLE_NAME);
Path rootTableDir = HTableDescriptor.getTableDir(
fs.makeQualified(new Path(conf.get(HBASE_DIR))),
ROOT_TABLE_NAME);
// Scan root region to find all the meta regions
root = new HRegion(rootTableDir, hlog, fs, conf,
HRegionInfo.ROOT_REGIONINFO, null, null);
InternalScanner rootScanner =
root.getScanner(COL_REGIONINFO_ARRAY, HConstants.EMPTY_START_ROW,
HConstants.LATEST_TIMESTAMP, null);
try {
HStoreKey key = new HStoreKey();
TreeMap<byte [], Cell> results =
new TreeMap<byte [], Cell>(Bytes.BYTES_COMPARATOR);
while(rootScanner.next(key, results)) {
for(Cell c: results.values()) {
HRegionInfo info = Writables.getHRegionInfoOrNull(c.getValue());
if (info != null) {
metaRegions.add(info);
}
}
}
} finally {
rootScanner.close();
try {
root.close();
} catch(IOException e) {
LOG.error(e);
}
}
}
@Override
protected HRegionInfo[] next() {
HRegionInfo[] results = null;
if (metaRegions.size() > 0) {
results = metaRegions.toArray(new HRegionInfo[metaRegions.size()]);
metaRegions.clear();
}
return results;
}
@Override
protected void updateMeta(final byte [] oldRegion1,
final byte [] oldRegion2, HRegion newRegion)
throws IOException {
byte[][] regionsToDelete = {oldRegion1, oldRegion2};
for(int r = 0; r < regionsToDelete.length; r++) {
BatchUpdate b = new BatchUpdate(regionsToDelete[r]);
b.delete(COL_REGIONINFO);
b.delete(COL_SERVER);
b.delete(COL_STARTCODE);
b.delete(COL_SPLITA);
b.delete(COL_SPLITB);
root.batchUpdate(b);
if(LOG.isDebugEnabled()) {
LOG.debug("updated columns in row: " + regionsToDelete[r]);
}
}
HRegionInfo newInfo = newRegion.getRegionInfo();
newInfo.setOffline(true);
BatchUpdate b = new BatchUpdate(newRegion.getRegionName());
b.put(COL_REGIONINFO, Writables.getBytes(newInfo));
root.batchUpdate(b);
if(LOG.isDebugEnabled()) {
LOG.debug("updated columns in row: " + newRegion.getRegionName());
}
}
}
}