com.alibaba.druid.pool.ha.balance.LeastConnectionBalancer Maven / Gradle / Ivy

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An JDBC datasource implementation.

There is a newer version: 1.2.23

package com.alibaba.druid.pool.ha.balance;

import java.sql.SQLException;

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;

public class LeastConnectionBalancer extends AbstractBalancer {

    @Override
    public void afterDataSourceChanged(DataSourceChangedEvent event) {

    }

    @Override
    public MultiConnectionHolder getConnection(MultiDataSourceConnection conn, String sql) throws SQLException {
        MultiDataSource multiDataSource = conn.getMultiDataSource();

        DataSourceHolder dataSource = null;
        int leastCount = -1;

        for (DataSourceHolder item : multiDataSource.getDataSources().values()) {
            if (!item.isEnable()) {
                continue;
            }

            int activeCount = item.getDataSource().getActiveCount();
            if (dataSource == null) {
                leastCount = activeCount;
                dataSource = item;
            } else {
                if (leastCount > item.getDataSource().getActiveCount()) {
                    dataSource = item;
                    leastCount = activeCount;
                }
            }
        }

        if (dataSource == null) {
            throw new SQLException("can not get real connection, enableDataSourceCount "
                                   + multiDataSource.getEnabledDataSourceCount());
        }

        return dataSource.getConnection();
    }

}