/*
* 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.hbase.index.table;
import java.io.IOException;
import java.util.Map;
import org.apache.commons.collections.map.LRUMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.client.HTableInterface;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hbase.index.util.ImmutableBytesPtr;
/**
* A simple cache that just uses usual GC mechanisms to cleanup unused {@link HTableInterface}s.
* When requesting an {@link HTableInterface} via {@link #getTable}, you may get the same table as
* last time, or it may be a new table.
* <p>
* You <b>should not call {@link HTableInterface#close()} </b> that is handled when the table goes
* out of scope. Along the same lines, you must ensure to not keep a reference to the table for
* longer than necessary - this leak will ensure that the table never gets closed.
*/
public class CachingHTableFactory implements HTableFactory {
/**
* LRUMap that closes the {@link HTableInterface} when the table is evicted
*/
@SuppressWarnings("serial")
public class HTableInterfaceLRUMap extends LRUMap {
public HTableInterfaceLRUMap(int cacheSize) {
super(cacheSize);
}
@Override
protected boolean removeLRU(LinkEntry entry) {
HTableInterface table = (HTableInterface) entry.getValue();
if (LOG.isDebugEnabled()) {
LOG.debug("Closing connection to table: " + Bytes.toString(table.getTableName())
+ " because it was evicted from the cache.");
}
try {
table.close();
} catch (IOException e) {
LOG.info("Failed to correctly close HTable: " + Bytes.toString(table.getTableName())
+ " ignoring since being removed from queue.");
}
return true;
}
}
public static int getCacheSize(Configuration conf) {
return conf.getInt(CACHE_SIZE_KEY, DEFAULT_CACHE_SIZE);
}
private static final Log LOG = LogFactory.getLog(CachingHTableFactory.class);
private static final String CACHE_SIZE_KEY = "index.tablefactory.cache.size";
private static final int DEFAULT_CACHE_SIZE = 10;
private HTableFactory delegate;
@SuppressWarnings("rawtypes")
Map openTables;
public CachingHTableFactory(HTableFactory tableFactory, Configuration conf) {
this(tableFactory, getCacheSize(conf));
}
public CachingHTableFactory(HTableFactory factory, int cacheSize) {
this.delegate = factory;
openTables = new HTableInterfaceLRUMap(cacheSize);
}
@Override
@SuppressWarnings("unchecked")
public HTableInterface getTable(ImmutableBytesPtr tablename) throws IOException {
ImmutableBytesPtr tableBytes = new ImmutableBytesPtr(tablename);
synchronized (openTables) {
HTableInterface table = (HTableInterface) openTables.get(tableBytes);
if (table == null) {
table = delegate.getTable(tablename);
openTables.put(tableBytes, table);
}
return table;
}
}
@Override
public void shutdown() {
this.delegate.shutdown();
}
}