content: // 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
  // 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.cloud.utils.db;
  
  import java.lang.reflect.InvocationHandler;
  import java.sql.SQLException;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.LogManager;
  
  import com.mysql.cj.jdbc.ConnectionImpl;
  import com.mysql.cj.jdbc.JdbcConnection;
  import com.mysql.cj.jdbc.exceptions.SQLError;
  import com.mysql.cj.jdbc.ha.BalanceStrategy;
  import com.mysql.cj.jdbc.ha.LoadBalancedConnectionProxy;
  
  public class StaticStrategy implements BalanceStrategy {
      protected Logger logger = LogManager.getLogger(getClass());
  
      public StaticStrategy() {
      }
  
      @Override
      public JdbcConnection pickConnection(InvocationHandler proxy, List<String> configuredHosts, Map<String, JdbcConnection> liveConnections,
                                           long[] responseTimes, int numRetries) throws SQLException {
          int numHosts = configuredHosts.size();
  
          SQLException ex = null;
  
          List<String> allowList = new ArrayList<String>(numHosts);
          allowList.addAll(configuredHosts);
  
          Map<String, Long> denylist = ((LoadBalancedConnectionProxy) proxy).getGlobalBlacklist();
  
          allowList.removeAll(denylist.keySet());
  
          Map<String, Integer> allowListMap = this.getArrayIndexMap(allowList);
  
          for (int attempts = 0; attempts < numRetries;) {
              if (allowList.size() == 0) {
                  throw SQLError.createSQLException("No hosts configured", null);
              }
  
              String hostPortSpec = allowList.get(0);     //Always take the first host
  
              ConnectionImpl conn = (ConnectionImpl) liveConnections.get(hostPortSpec);
  
              if (conn == null) {
                  try {
                      conn = ((LoadBalancedConnectionProxy) proxy).createConnectionForHost(hostPortSpec);
                  } catch (SQLException sqlEx) {
                      ex = sqlEx;
  
                      if (((LoadBalancedConnectionProxy) proxy).shouldExceptionTriggerFailover(sqlEx)) {
  
                          Integer allowListIndex = allowListMap.get(hostPortSpec);
  
                          // exclude this host from being picked again
                          if (allowListIndex != null) {
                              allowList.remove(allowListIndex.intValue());
                              allowListMap = this.getArrayIndexMap(allowList);
                          }
                          ((LoadBalancedConnectionProxy) proxy).addToGlobalBlacklist(hostPortSpec);
  
                          if (allowList.size() == 0) {
                              attempts++;
                              try {
                                  Thread.sleep(250);
                              } catch (InterruptedException e) {
                                  logger.debug("[ignored] interrupted while fail over in progres.");
                              }
  
                              // start fresh
                              allowListMap = new HashMap<String, Integer>(numHosts);
                              allowList.addAll(configuredHosts);
                              denylist = ((LoadBalancedConnectionProxy) proxy).getGlobalBlacklist();
  
                              allowList.removeAll(denylist.keySet());
                              allowListMap = this.getArrayIndexMap(allowList);
                          }
  
                          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), i);
          }
          return m;
  
      }
  }
  