thinkphp下MySQL数据库读写分离代码剖析

  /**
   * SQL查询
   * @access public
   * @param string $sql SQL
   * @param mixed $parse 是否需要解析SQL 
   * @return mixed
   */
  public function query($sql,$parse=false) {
    if(!is_bool($parse) && !is_array($parse)) {
      $parse = func_get_args();
      array_shift($parse);
    }
    $sql =  $this->parseSql($sql,$parse);
    return $this->db->query($sql);
  }
  

  /**
   * 执行查询 返回数据集
   * @access public
   * @param string $str sql指令
   * @return mixed
   */
  public function query($str) {
    if(0===stripos($str, 'call')){ // 存储过程查询支持
      $this->close();
      $this->connected  =  false;
    }
    $this->initConnect(false);
    if ( !$this->_linkID ) return false;
    $this->queryStr = $str;
    //释放前次的查询结果
    if ( $this->queryID ) {  $this->free();  }
    N('db_query',1);
    // 记录开始执行时间
    G('queryStartTime');
    $this->queryID = mysql_query($str, $this->_linkID);
    $this->debug();
    if ( false === $this->queryID ) {
      $this->error();
      return false;
    } else {
      $this->numRows = mysql_num_rows($this->queryID);
      return $this->getAll();
    }
  }

  /**
   * 初始化数据库连接
   * @access protected
   * @param boolean $master 主服务器
   * @return void
   */
  protected function initConnect($master=true) {
    if(1 == C('DB_DEPLOY_TYPE'))
      // 采用分布式数据库
      $this->_linkID = $this->multiConnect($master);
    else
      // 默认单数据库
      if ( !$this->connected ) $this->_linkID = $this->connect();
  }

  /**
   * 连接分布式服务器
   * @access protected
   * @param boolean $master 主服务器
   * @return void
   */
  protected function multiConnect($master=false) {
    foreach ($this->config as $key=>$val){
      $_config[$key]   =  explode(',',$val);
    }    
    // 数据库读写是否分离
    if(C('DB_RW_SEPARATE')){
      // 主从式采用读写分离
      if($master)
        // 主服务器写入
        $r =  floor(mt_rand(0,C('DB_MASTER_NUM')-1));
      else{
        if(is_numeric(C('DB_SLAVE_NO'))) {// 指定服务器读
          $r = C('DB_SLAVE_NO');
        }else{
          // 读操作连接从服务器
          $r = floor(mt_rand(C('DB_MASTER_NUM'),count($_config['hostname'])-1));  // 每次随机连接的数据库
        }
      }
    }else{
      // 读写操作不区分服务器
      $r = floor(mt_rand(0,count($_config['hostname'])-1));  // 每次随机连接的数据库
    }
    $db_config = array(
      'username' => isset($_config['username'][$r])?$_config['username'][$r]:$_config['username'][0],
      'password' => isset($_config['password'][$r])?$_config['password'][$r]:$_config['password'][0],
      'hostname' => isset($_config['hostname'][$r])?$_config['hostname'][$r]:$_config['hostname'][0],
      'hostport' => isset($_config['hostport'][$r])?$_config['hostport'][$r]:$_config['hostport'][0],
      'database' => isset($_config['database'][$r])?$_config['database'][$r]:$_config['database'][0],
      'dsn'    => isset($_config['dsn'][$r])?$_config['dsn'][$r]:$_config['dsn'][0],
      'params'  => isset($_config['params'][$r])?$_config['params'][$r]:$_config['params'][0],
      'charset'  => isset($_config['charset'][$r])?$_config['charset'][$r]:$_config['charset'][0],      
    );
    return $this->connect($db_config,$r);
  }