/*
* Copyright 1999-2011 Alibaba Group Holding Ltd.
*
* Licensed 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 com.alibaba.druid.pool.ha.balance;
import java.sql.SQLException;
import java.util.concurrent.atomic.AtomicInteger;
import com.alibaba.druid.pool.ha.DataSourceChangedEvent;
import com.alibaba.druid.pool.ha.DataSourceHolder;
import com.alibaba.druid.pool.ha.MultiConnectionHolder;
import com.alibaba.druid.pool.ha.MultiDataSource;
import com.alibaba.druid.pool.ha.MultiDataSourceConnection;
import com.alibaba.druid.support.logging.Log;
import com.alibaba.druid.support.logging.LogFactory;
public class RoundRobinBlancer extends AbstractBalancer {
private final static Log LOG = LogFactory.getLog(RoundRobinBlancer.class);
private final AtomicInteger indexErrorCount = new AtomicInteger();
public RoundRobinBlancer(){
}
public void afterDataSourceChanged(DataSourceChangedEvent event) {
}
@Override
public MultiConnectionHolder getConnection(MultiDataSourceConnection conn, String sql) throws SQLException {
MultiDataSource multiDataSource = conn.getMultiDataSource();
int size = multiDataSource.getDataSources().size();
long connectionId = (int) conn.getId();
if (size == 0) {
throw new SQLException("can not get connection, no availabe datasources");
}
int index = (int) (connectionId % size);
DataSourceHolder first = null;
DataSourceHolder dataSource = null;
try {
int itemIndex = 0;
for (DataSourceHolder item : multiDataSource.getDataSources().values()) {
if (!item.isEnable()) {
continue;
}
if (first == null) {
first = item;
}
if (itemIndex == index) {
dataSource = item;
break;
}
itemIndex++;
}
if (dataSource == null) {
dataSource = first;
}
} catch (Exception ex) {
indexErrorCount.incrementAndGet();
if (LOG.isDebugEnabled()) {
LOG.debug("getDataSource error, index : " + index, ex);
}
}
if (dataSource == null) {
throw new SQLException("can not get real connection.");
}
MultiConnectionHolder holder = null;
return holder;
}
public long getIndexErrorCount() {
return indexErrorCount.get();
}
}