StaticStrategy.java

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// 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
// the License.  You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
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package com.cloud.utils.db;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;

import com.mysql.jdbc.BalanceStrategy;
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.ConnectionImpl;
import com.mysql.jdbc.LoadBalancingConnectionProxy;
import com.mysql.jdbc.SQLError;

public class StaticStrategy implements BalanceStrategy {

    public StaticStrategy() {
    }

    @Override
    public void destroy() {
        // we don't have anything to clean up
    }

    @Override
    public void init(Connection conn, Properties props) throws SQLException {
        // we don't have anything to initialize
    }

    @Override
    public ConnectionImpl pickConnection(LoadBalancingConnectionProxy proxy, List<String> configuredHosts, Map<String, ConnectionImpl> liveConnections,
        long[] responseTimes, int numRetries) throws SQLException {
        int numHosts = configuredHosts.size();

        SQLException ex = null;

        List<String> whiteList = new ArrayList<String>(numHosts);
        whiteList.addAll(configuredHosts);

        Map<String, Long> blackList = proxy.getGlobalBlacklist();

        whiteList.removeAll(blackList.keySet());

        Map<String, Integer> whiteListMap = this.getArrayIndexMap(whiteList);

        for (int attempts = 0; attempts < numRetries;) {
            if (whiteList.size() == 0) {
                throw SQLError.createSQLException("No hosts configured", null);
            }

            String hostPortSpec = whiteList.get(0);     //Always take the first host

            ConnectionImpl conn = liveConnections.get(hostPortSpec);

            if (conn == null) {
                try {
                    conn = proxy.createConnectionForHost(hostPortSpec);
                } catch (SQLException sqlEx) {
                    ex = sqlEx;

                    if (proxy.shouldExceptionTriggerFailover(sqlEx)) {

                        Integer whiteListIndex = whiteListMap.get(hostPortSpec);

                        // exclude this host from being picked again
                        if (whiteListIndex != null) {
                            whiteList.remove(whiteListIndex.intValue());
                            whiteListMap = this.getArrayIndexMap(whiteList);
                        }
                        proxy.addToGlobalBlacklist(hostPortSpec);

                        if (whiteList.size() == 0) {
                            attempts++;
                            try {
                                Thread.sleep(250);
                            } catch (InterruptedException e) {
                            }

                            // start fresh
                            whiteListMap = new HashMap<String, Integer>(numHosts);
                            whiteList.addAll(configuredHosts);
                            blackList = proxy.getGlobalBlacklist();

                            whiteList.removeAll(blackList.keySet());
                            whiteListMap = this.getArrayIndexMap(whiteList);
                        }

                        continue;
                    }

                    throw sqlEx;
                }
            }

            return conn;
        }

        if (ex != null) {
            throw ex;
        }

        return null; // we won't get here, compiler can't tell
    }

    private Map<String, Integer> getArrayIndexMap(List<String> l) {
        Map<String, Integer> m = new HashMap<String, Integer>(l.size());
        for (int i = 0; i < l.size(); i++) {
            m.put(l.get(i), Integer.valueOf(i));
        }
        return m;

    }

}