/**
* 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.master.balancer;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.ClusterStatus;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.HDFSBlocksDistribution;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.HTableDescriptor;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.master.MasterServices;
import org.apache.hadoop.hbase.regionserver.HRegion;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
/**
* This will find where data for a region is located in HDFS. It ranks
* {@link ServerName}'s by the size of the store files they are holding for a
* given region.
*
*/
class RegionLocationFinder {
private static Log LOG = LogFactory.getLog(RegionLocationFinder.class);
private Configuration conf;
private ClusterStatus status;
private MasterServices services;
private CacheLoader<HRegionInfo, List<ServerName>> loader =
new CacheLoader<HRegionInfo, List<ServerName>>() {
@Override
public List<ServerName> load(HRegionInfo key) throws Exception {
List<ServerName> servers = internalGetTopBlockLocation(key);
if (servers == null) {
return new LinkedList<ServerName>();
}
return servers;
}
};
// The cache for where regions are located.
private LoadingCache<HRegionInfo, List<ServerName>> cache = null;
/**
* Create a cache for region to list of servers
* @param mins Number of mins to cache
* @return A new Cache.
*/
private LoadingCache<HRegionInfo, List<ServerName>> createCache(int mins) {
return CacheBuilder.newBuilder().expireAfterAccess(mins, TimeUnit.MINUTES).build(loader);
}
public Configuration getConf() {
return conf;
}
public void setConf(Configuration conf) {
this.conf = conf;
cache = createCache(conf.getInt("hbase.master.balancer.regionLocationCacheTime", 30));
}
public void setServices(MasterServices services) {
this.services = services;
}
public void setClusterStatus(ClusterStatus status) {
this.status = status;
}
protected List<ServerName> getTopBlockLocations(HRegionInfo region) {
List<ServerName> servers = null;
try {
servers = cache.get(region);
} catch (ExecutionException ex) {
servers = new LinkedList<ServerName>();
}
return servers;
}
/**
* Returns an ordered list of hosts that are hosting the blocks for this
* region. The weight of each host is the sum of the block lengths of all
* files on that host, so the first host in the list is the server which holds
* the most bytes of the given region's HFiles.
*
* @param region region
* @return ordered list of hosts holding blocks of the specified region
*/
protected List<ServerName> internalGetTopBlockLocation(HRegionInfo region) {
List<ServerName> topServerNames = null;
try {
HTableDescriptor tableDescriptor = getTableDescriptor(region.getTableName());
if (tableDescriptor != null) {
HDFSBlocksDistribution blocksDistribution =
HRegion.computeHDFSBlocksDistribution(getConf(), tableDescriptor, region);
List<String> topHosts = blocksDistribution.getTopHosts();
topServerNames = mapHostNameToServerName(topHosts);
}
} catch (IOException ioe) {
LOG.debug("IOException during HDFSBlocksDistribution computation. for " + "region = "
+ region.getEncodedName(), ioe);
}
return topServerNames;
}
/**
* return HTableDescriptor for a given tableName
*
* @param tableName the table name
* @return HTableDescriptor
* @throws IOException
*/
protected HTableDescriptor getTableDescriptor(TableName tableName) throws IOException {
HTableDescriptor tableDescriptor = null;
try {
if (this.services != null) {
tableDescriptor = this.services.getTableDescriptors().get(tableName);
}
} catch (FileNotFoundException fnfe) {
LOG.debug("FileNotFoundException during getTableDescriptors." + " Current table name = "
+ tableName, fnfe);
}
return tableDescriptor;
}
/**
* Map hostname to ServerName, The output ServerName list will have the same
* order as input hosts.
*
* @param hosts the list of hosts
* @return ServerName list
*/
protected List<ServerName> mapHostNameToServerName(List<String> hosts) {
if (hosts == null || status == null) {
return null;
}
List<ServerName> topServerNames = new ArrayList<ServerName>();
Collection<ServerName> regionServers = status.getServers();
// create a mapping from hostname to ServerName for fast lookup
HashMap<String, ServerName> hostToServerName = new HashMap<String, ServerName>();
for (ServerName sn : regionServers) {
hostToServerName.put(sn.getHostname(), sn);
}
for (String host : hosts) {
ServerName sn = hostToServerName.get(host);
// it is possible that HDFS is up ( thus host is valid ),
// but RS is down ( thus sn is null )
if (sn != null) {
topServerNames.add(sn);
}
}
return topServerNames;
}
}