content: /*
   * Copyright (c) 2010, 2020, Oracle and/or its affiliates.
   *
   * This program is free software; you can redistribute it and/or modify it under
   * the terms of the GNU General Public License, version 2.0, as published by the
   * Free Software Foundation.
   *
   * This program is also distributed with certain software (including but not
   * limited to OpenSSL) that is licensed under separate terms, as designated in a
   * particular file or component or in included license documentation. The
   * authors of MySQL hereby grant you an additional permission to link the
   * program and your derivative works with the separately licensed software that
   * they have included with MySQL.
   *
   * Without limiting anything contained in the foregoing, this file, which is
   * part of MySQL Connector/J, is also subject to the Universal FOSS Exception,
   * version 1.0, a copy of which can be found at
   * http://oss.oracle.com/licenses/universal-foss-exception.
   *
   * This program is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
   * FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0,
   * for more details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
   */
  
  package com.mysql.cj.jdbc.ha;
  
  import java.sql.SQLException;
  import java.util.Properties;
  import java.util.function.Supplier;
  
  import com.mysql.cj.MysqlConnection;
  import com.mysql.cj.Query;
  import com.mysql.cj.conf.PropertyKey;
  import com.mysql.cj.exceptions.ExceptionFactory;
  import com.mysql.cj.interceptors.QueryInterceptor;
  import com.mysql.cj.jdbc.JdbcConnection;
  import com.mysql.cj.log.Log;
  import com.mysql.cj.protocol.Resultset;
  import com.mysql.cj.protocol.ServerSession;
  import com.mysql.cj.util.StringUtils;
  
  public class LoadBalancedAutoCommitInterceptor implements QueryInterceptor {
      private int matchingAfterStatementCount = 0;
      private int matchingAfterStatementThreshold = 0;
      private String matchingAfterStatementRegex;
      private JdbcConnection conn;
      private LoadBalancedConnectionProxy proxy = null;
  
      private boolean countStatements = false;
  
      @Override
      public void destroy() {
          this.conn = null;
          this.proxy = null;
      }
  
      @Override
      public boolean executeTopLevelOnly() {
          // always return false
          return false;
      }
  
      @Override
      public QueryInterceptor init(MysqlConnection connection, Properties props, Log log) {
          this.conn = (JdbcConnection) connection;
  
          String autoCommitSwapThresholdAsString = props.getProperty(PropertyKey.loadBalanceAutoCommitStatementThreshold.getKeyName(), "0");
          try {
              this.matchingAfterStatementThreshold = Integer.parseInt(autoCommitSwapThresholdAsString);
          } catch (NumberFormatException nfe) {
              // nothing here, being handled in LoadBalancedConnectionProxy.
          }
          String autoCommitSwapRegex = props.getProperty(PropertyKey.loadBalanceAutoCommitStatementRegex.getKeyName(), "");
          if (!"".equals(autoCommitSwapRegex)) {
              this.matchingAfterStatementRegex = autoCommitSwapRegex;
          }
          return this;
  
      }
  
      @Override
      @SuppressWarnings("resource")
      public <T extends Resultset> T postProcess(Supplier<String> sql, Query interceptedQuery, T originalResultSet, ServerSession serverSession) {
  
          try {
              // Don't count SETs, SHOWs neither USEs. Those are mostly used internally and must not trigger a connection switch.
              if (!this.countStatements || StringUtils.startsWithIgnoreCase(sql.get(), "SET") || StringUtils.startsWithIgnoreCase(sql.get(), "SHOW")
                      || StringUtils.startsWithIgnoreCase(sql.get(), "USE")) {
                  return originalResultSet;
              }
  
              // Don't care if auto-commit is not enabled.
              if (!this.conn.getAutoCommit()) {
                  this.matchingAfterStatementCount = 0;
                  return originalResultSet;
              }
  
              if (this.proxy == null && this.conn.isProxySet()) {
                  JdbcConnection connParentProxy = this.conn.getMultiHostParentProxy();
                  while (connParentProxy != null && !(connParentProxy instanceof LoadBalancedMySQLConnection)) {
                      connParentProxy = connParentProxy.getMultiHostParentProxy();
                  }
                  if (connParentProxy != null) {
                      this.proxy = ((LoadBalancedMySQLConnection) connParentProxy).getThisAsProxy();
                  }
              }
  
              // Connection is not ready to rebalance yet.
              if (this.proxy == null) {
                  return originalResultSet;
              }
  
              // Increment the match count if no regex specified, or if matches.
              if (this.matchingAfterStatementRegex == null || sql.get().matches(this.matchingAfterStatementRegex)) {
                  this.matchingAfterStatementCount++;
              }
  
              // Trigger rebalance if count exceeds threshold.
              if (this.matchingAfterStatementCount >= this.matchingAfterStatementThreshold) {
                  this.matchingAfterStatementCount = 0;
                  try {
                      this.proxy.pickNewConnection();
                  } catch (SQLException e) {
                      // eat this exception, the auto-commit statement completed, but we could not rebalance for some reason.  User may get exception when using
                      // connection next.
                  }
              }
          } catch (SQLException ex) {
              throw ExceptionFactory.createException(ex.getMessage(), ex);
          }
          // always return the original result set.
          return originalResultSet;
      }
  
      @Override
      public <T extends Resultset> T preProcess(Supplier<String> sql, Query interceptedQuery) {
          // we do nothing before execution, it's unsafe to swap servers at this point.
          return null;
      }
  
      void pauseCounters() {
          this.countStatements = false;
      }
  
      void resumeCounters() {
          this.countStatements = true;
      }
  }
  