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Differences Between: [Versions 311 and 400] [Versions 400 and 401] [Versions 400 and 402] [Versions 400 and 403]

   1  <?php
   2  /**
   3   * ADOdb Load Balancer
   4   *
   5   * ADOdbLoadBalancer is a class that allows the user to do read/write splitting
   6   * and load balancing across multiple servers. It can handle and load balance
   7   * any number of write capable (AKA: master) or readonly (AKA: slave) connections,
   8   * including dealing with connection failures and retrying queries on a different
   9   * connection instead.
  10   *
  11   * This file is part of ADOdb, a Database Abstraction Layer library for PHP.
  12   *
  13   * @package ADOdb
  14   * @link https://adodb.org Project's web site and documentation
  15   * @link https://github.com/ADOdb/ADOdb Source code and issue tracker
  16   *
  17   * The ADOdb Library is dual-licensed, released under both the BSD 3-Clause
  18   * and the GNU Lesser General Public Licence (LGPL) v2.1 or, at your option,
  19   * any later version. This means you can use it in proprietary products.
  20   * See the LICENSE.md file distributed with this source code for details.
  21   * @license BSD-3-Clause
  22   * @license LGPL-2.1-or-later
  23   *
  24   * @copyright 2016 Mike Benoit and the ADOdb community
  25   */
  26  
  27  /**
  28   * Class ADOdbLoadBalancer
  29   */
  30  class ADOdbLoadBalancer
  31  {
  32      /**
  33       * @var bool    Once a write or readonly connection is made, stick to that connection for the entire request.
  34       */
  35      public $enable_sticky_sessions = true;
  36  
  37  
  38      /**
  39       * @var bool|array    All connections to each database.
  40       */
  41      protected $connections = false;
  42  
  43      /**
  44       * @var bool|array    Just connections to the write capable database.
  45       */
  46      protected $connections_write = false;
  47  
  48      /**
  49       * @var bool|array    Just connections to the readonly database.
  50       */
  51      protected $connections_readonly = false;
  52  
  53      /**
  54       * @var array    Counts of all connections and their types.
  55       */
  56      protected $total_connections = array('all' => 0, 'write' => 0, 'readonly' => 0);
  57  
  58      /**
  59       * @var array    Weights of all connections for each type.
  60       */
  61      protected $total_connection_weights = array('all' => 0, 'write' => 0, 'readonly' => 0);
  62  
  63      /**
  64       * @var bool    When in transactions, always use this connection.
  65       */
  66      protected $pinned_connection_id = false;
  67  
  68      /**
  69       * @var array    Last connection_id for each database type.
  70       */
  71      protected $last_connection_id = array('write' => false, 'readonly' => false, 'all' => false);
  72  
  73      /**
  74       * @var bool    Session variables that must be maintained across all connections, ie: SET TIME ZONE.
  75       */
  76      protected $session_variables = false;
  77  
  78      /**
  79       * @var bool    Called immediately after connecting to any DB.
  80       */
  81      protected $user_defined_session_init_sql = false;
  82  
  83  
  84      /**
  85       * Defines SQL queries that are executed each time a new database connection is established.
  86       *
  87       * @param  $sql
  88       * @return bool
  89       */
  90      public function setSessionInitSQL($sql)
  91      {
  92          $this->user_defined_session_init_sql[] = $sql;
  93  
  94          return true;
  95      }
  96  
  97      /**
  98       * Adds a new database connection to the pool, but no actual connection is made until its needed.
  99       *
 100       * @param  $obj
 101       * @return bool
 102       * @throws Exception
 103       */
 104      public function addConnection($obj)
 105      {
 106          if ($obj instanceof ADOdbLoadBalancerConnection) {
 107              $this->connections[] = $obj;
 108              end($this->connections);
 109              $i = key($this->connections);
 110  
 111              $this->total_connections[$obj->type]++;
 112              $this->total_connections['all']++;
 113  
 114              $this->total_connection_weights[$obj->type] += abs($obj->weight);
 115              $this->total_connection_weights['all'] += abs($obj->weight);
 116  
 117              if ($obj->type == 'write') {
 118                  $this->connections_write[] = $i;
 119              } else {
 120                  $this->connections_readonly[] = $i;
 121              }
 122  
 123              return true;
 124          }
 125  
 126          throw new Exception('Connection object is not an instance of ADOdbLoadBalancerConnection');
 127      }
 128  
 129      /**
 130       * Removes a database connection from the pool.
 131       *
 132       * @param  $i
 133       * @return bool
 134       */
 135      public function removeConnection($i)
 136      {
 137          if (isset($this->connections[$i])) {
 138                 $obj = $this->connections[ $i ];
 139  
 140                 $this->total_connections[ $obj->type ]--;
 141                 $this->total_connections['all']--;
 142  
 143                 $this->total_connection_weights[ $obj->type ] -= abs($obj->weight);
 144                 $this->total_connection_weights['all'] -= abs($obj->weight);
 145  
 146              if ($obj->type == 'write') {
 147                  unset($this->connections_write[array_search($i, $this->connections_write)]);
 148                  // Reindex array.
 149                  $this->connections_write = array_values($this->connections_write);
 150              } else {
 151                  unset($this->connections_readonly[array_search($i, $this->connections_readonly)]);
 152                  // Reindex array.
 153                  $this->connections_readonly = array_values($this->connections_readonly);
 154              }
 155  
 156              // Remove any sticky connections as well.
 157              if ($this->last_connection_id[$obj->type] == $i) {
 158                  $this->last_connection_id[$obj->type] = false;
 159              }
 160  
 161              unset($this->connections[$i]);
 162  
 163              return true;
 164          }
 165  
 166          return false;
 167      }
 168  
 169      /**
 170       * Returns a database connection of the specified type.
 171       *
 172       * Takes into account the connection weight for load balancing.
 173       *
 174       * @param  string $type Type of database connection, either: 'write' capable or 'readonly'
 175       * @return bool|int|string
 176       */
 177      private function getConnectionByWeight($type)
 178      {
 179          if ($type == 'readonly') {
 180              $total_weight = $this->total_connection_weights['all'];
 181          } else {
 182              $total_weight = $this->total_connection_weights['write'];
 183          }
 184  
 185          $i = false;
 186          if (is_array($this->connections)) {
 187              $n = 0;
 188              $num = mt_rand(0, $total_weight);
 189              foreach ($this->connections as $i => $connection_obj) {
 190                  if ($connection_obj->weight > 0 && ($type == 'readonly' || $connection_obj->type == 'write')) {
 191                      $n += $connection_obj->weight;
 192                      if ($n >= $num) {
 193                          break;
 194                      }
 195                  }
 196              }
 197          }
 198  
 199          return $i;
 200      }
 201  
 202      /**
 203       * Returns the proper database connection when taking into account sticky sessions and load balancing.
 204       *
 205       * @param  $type
 206       * @return bool|int|mixed|string
 207       */
 208      public function getLoadBalancedConnection($type)
 209      {
 210          if ($this->total_connections == 0) {
 211              $connection_id = 0;
 212          } else {
 213              if ($this->enable_sticky_sessions == true && $this->last_connection_id[$type] !== false) {
 214                  $connection_id = $this->last_connection_id[$type];
 215              } else {
 216                  if ($type == 'write' && $this->total_connections['write'] == 1) {
 217                      $connection_id = $this->connections_write[0];
 218                  } else {
 219                      $connection_id = $this->getConnectionByWeight($type);
 220                  }
 221              }
 222          }
 223  
 224          return $connection_id;
 225      }
 226  
 227      /**
 228       * Returns the ADODB connection object by connection_id.
 229       *
 230       * Ensures that it's connected and the session variables are executed.
 231       *
 232       * @param  $connection_id
 233       * @return bool|ADOConnection
 234       * @throws Exception
 235       */
 236      private function _getConnection($connection_id)
 237      {
 238          if (isset($this->connections[$connection_id])) {
 239              $connection_obj = $this->connections[$connection_id];
 240              /** @var ADOConnection $adodb_obj */
 241              $adodb_obj = $connection_obj->getADOdbObject();
 242              if (is_object($adodb_obj) && $adodb_obj->_connectionID == false) {
 243                  try {
 244                      if ($connection_obj->persistent_connection == true) {
 245                          $adodb_obj->Pconnect(
 246                              $connection_obj->host,
 247                              $connection_obj->user,
 248                              $connection_obj->password,
 249                              $connection_obj->database
 250                          );
 251                      } else {
 252                          $adodb_obj->Connect(
 253                              $connection_obj->host,
 254                              $connection_obj->user,
 255                              $connection_obj->password,
 256                              $connection_obj->database
 257                          );
 258                      }
 259                  } catch (Exception $e) {
 260                      // Connection error, see if there are other connections to try still.
 261                      throw $e; // No connections left, reThrow exception so application can catch it.
 262                  }
 263  
 264                  if (is_array($this->user_defined_session_init_sql)) {
 265                      foreach ($this->user_defined_session_init_sql as $session_init_sql) {
 266                          $adodb_obj->Execute($session_init_sql);
 267                      }
 268                  }
 269                  $this->executeSessionVariables($adodb_obj);
 270              }
 271  
 272              return $adodb_obj;
 273          } else {
 274              throw new Exception('Unable to return Connection object...');
 275          }
 276      }
 277  
 278      /**
 279       * Returns the ADODB connection object by database type.
 280       *
 281       * Ensures that it's connected and the session variables are executed.
 282       *
 283       * @param  string $type
 284       * @param  null   $pin_connection
 285       * @return ADOConnection|bool
 286       * @throws Exception
 287       */
 288      public function getConnection($type = 'write', $pin_connection = null)
 289      {
 290          while (($type == 'write' && $this->total_connections['write'] > 0)
 291              || ($type == 'readonly' && $this->total_connections['all'] > 0)
 292          ) {
 293              if ($this->pinned_connection_id !== false) {
 294                  $connection_id = $this->pinned_connection_id;
 295              } else {
 296                  $connection_id = $this->getLoadBalancedConnection($type);
 297              }
 298  
 299              if ($connection_id !== false) {
 300                  try {
 301                      $adodb_obj = $this->_getConnection($connection_id);
 302                      // $connection_obj = $this->connections[$connection_id];
 303                      break;
 304                  } catch (Exception $e) {
 305                      // Connection error, see if there are other connections to try still.
 306                      $this->removeConnection($connection_id);
 307                      if (   ($type == 'write' && $this->total_connections['write'] == 0)
 308                          || ($type == 'readonly' && $this->total_connections['all'] == 0)
 309                      ) {
 310                          throw $e;
 311                      }
 312                  }
 313              } else {
 314                  throw new Exception('Connection ID is invalid!');
 315              }
 316          }
 317  
 318          $this->last_connection_id[$type] = $connection_id;
 319  
 320          if ($pin_connection === true) {
 321              $this->pinned_connection_id = $connection_id;
 322          } elseif ($pin_connection === false && $adodb_obj->transOff <= 1) {
 323              // UnPin connection only if we are 1 level deep in a transaction.
 324              $this->pinned_connection_id = false;
 325  
 326              // When unpinning connection, reset last_connection_id so readonly
 327              // queries don't get stuck on the write capable connection.
 328              $this->last_connection_id['write'] = false;
 329              $this->last_connection_id['readonly'] = false;
 330          }
 331  
 332          return $adodb_obj;
 333      }
 334  
 335      /**
 336       * This is a hack to work around pass by reference error.
 337       *
 338       * Parameter 1 to ADOConnection::GetInsertSQL() expected to be a reference,
 339       * value given in adodb-loadbalancer.inc.php on line 83
 340       *
 341       * @param  $arr
 342       * @return array
 343       */
 344      private function makeValuesReferenced($arr)
 345      {
 346          $refs = array();
 347  
 348          foreach ($arr as $key => $value) {
 349              $refs[$key] = &$arr[$key];
 350          }
 351  
 352          return $refs;
 353      }
 354  
 355      /**
 356       * Allow setting session variables that are maintained across connections.
 357       *
 358       * Its important that these are set using name/value, so it can determine
 359       * if the same variable is set multiple times causing bloat/clutter when
 360       * new connections are established. For example if the time_zone is set to
 361       * many different ones through the course of a single connection, a new
 362       * connection should only set it to the most recent value.
 363       *
 364       * @param  $name
 365       * @param  $value
 366       * @param  bool  $execute_immediately
 367       * @return array|bool|mixed
 368       * @throws Exception
 369       */
 370      public function setSessionVariable($name, $value, $execute_immediately = true)
 371      {
 372          $this->session_variables[$name] = $value;
 373  
 374          if ($execute_immediately == true) {
 375              return $this->executeSessionVariables();
 376          } else {
 377              return true;
 378          }
 379      }
 380  
 381      /**
 382       * Executes the session variables on a given ADODB object.
 383       *
 384       * @param  ADOConnection|bool $adodb_obj
 385       * @return array|bool|mixed
 386       * @throws Exception
 387       */
 388      private function executeSessionVariables($adodb_obj = false)
 389      {
 390          if (is_array($this->session_variables)) {
 391              $sql = '';
 392              foreach ($this->session_variables as $name => $value) {
 393                  // $sql .= 'SET SESSION '. $name .' '. $value;
 394                  // MySQL uses: SET SESSION foo_bar='foo'
 395                  // PGSQL uses: SET SESSION foo_bar 'foo'
 396                  // So leave it up to the user to pass the proper value with '=' if needed.
 397                  // This may be a candidate to move into ADOdb proper.
 398                  $sql .= 'SET SESSION ' . $name . ' ' . $value;
 399              }
 400  
 401              if ($adodb_obj !== false) {
 402                  return $adodb_obj->Execute($sql);
 403              } else {
 404                  return $this->ClusterExecute($sql);
 405              }
 406          }
 407  
 408          return false;
 409      }
 410  
 411      /**
 412       * Executes the same SQL QUERY on the entire cluster of connections.
 413       * Would be used for things like SET SESSION TIME ZONE calls and such.
 414       *
 415       * @param  $sql
 416       * @param  bool $inputarr
 417       * @param  bool $return_all_results
 418       * @param  bool $existing_connections_only
 419       * @return array|bool|mixed
 420       * @throws Exception
 421       */
 422      public function clusterExecute(
 423          $sql,
 424          $inputarr = false,
 425          $return_all_results = false,
 426          $existing_connections_only = true
 427      ) {
 428          if (is_array($this->connections) && count($this->connections) > 0) {
 429              foreach ($this->connections as $key => $connection_obj) {
 430                  if ($existing_connections_only == false
 431                      || ($existing_connections_only == true
 432                          && $connection_obj->getADOdbObject()->_connectionID !== false
 433                      )
 434                  ) {
 435                      $adodb_obj = $this->_getConnection($key);
 436                      if (is_object($adodb_obj)) {
 437                          $result_arr[] = $adodb_obj->Execute($sql, $inputarr);
 438                      }
 439                  }
 440              }
 441  
 442              if (isset($result_arr) && $return_all_results == true) {
 443                  return $result_arr;
 444              } else {
 445                  // Loop through all results checking to see if they match, if they do return the first one
 446                  // otherwise return an array of all results.
 447                  if (isset($result_arr)) {
 448                      foreach ($result_arr as $result) {
 449                          if ($result == false) {
 450                              return $result_arr;
 451                          }
 452                      }
 453  
 454                      return $result_arr[0];
 455                  } else {
 456                      // When using lazy connections, there are cases where
 457                      // setSessionVariable() is called early on, but there are
 458                      // no connections to execute the queries on yet.
 459                      // This captures that case and forces a RETURN TRUE to occur.
 460                      // As likely the queries will be executed as soon as a
 461                      // connection is established.
 462                      return true;
 463                  }
 464              }
 465          }
 466  
 467          return false;
 468      }
 469  
 470      /**
 471       * Determines if a SQL query is read-only or not.
 472       *
 473       * @param  string $sql SQL Query to test.
 474       * @return bool
 475       */
 476      public function isReadOnlyQuery($sql)
 477      {
 478          if (   stripos($sql, 'SELECT') === 0
 479              && stripos($sql, 'FOR UPDATE') === false
 480              && stripos($sql, ' INTO ') === false
 481              && stripos($sql, 'LOCK IN') === false
 482          ) {
 483              return true;
 484          }
 485  
 486          return false;
 487      }
 488  
 489      /**
 490       * Use this instead of __call() as it significantly reduces the overhead of call_user_func_array().
 491       *
 492       * @param  $sql
 493       * @param  bool $inputarr
 494       * @return array|bool|mixed
 495       * @throws Exception
 496       */
 497      public function execute($sql, $inputarr = false)
 498      {
 499          $type = 'write';
 500          $pin_connection = null;
 501  
 502          // Prevent leading spaces from causing isReadOnlyQuery/stripos from failing.
 503          $sql = trim($sql);
 504  
 505          // SELECT queries that can write and therefore must be run on a write capable connection.
 506          // SELECT ... FOR UPDATE;
 507          // SELECT ... INTO ...
 508          // SELECT .. LOCK IN ... (MYSQL)
 509          if ($this->isReadOnlyQuery($sql) == true) {
 510              $type = 'readonly';
 511          } elseif (stripos($sql, 'SET') === 0) {
 512              // SET SQL statements should likely use setSessionVariable() instead,
 513              // so state is properly maintained across connections, especially when they are lazily created.
 514              return $this->ClusterExecute($sql, $inputarr);
 515          }
 516  
 517          $adodb_obj = $this->getConnection($type, $pin_connection);
 518          if ($adodb_obj !== false) {
 519              return $adodb_obj->Execute($sql, $inputarr);
 520          }
 521  
 522          return false;
 523      }
 524  
 525      /**
 526       * Magic method to intercept method and callback to the proper ADODB object for write/readonly connections.
 527       *
 528       * @param  string $method ADODB method to call.
 529       * @param  array  $args   Arguments to the ADODB method.
 530       * @return bool|mixed
 531       * @throws Exception
 532       */
 533      public function __call($method, $args)
 534      {
 535          $type = 'write';
 536          $pin_connection = null;
 537  
 538          // Intercept specific methods to determine if they are read-only or not.
 539          $method = strtolower($method);
 540          switch ($method) {
 541              // case 'execute': // This is the direct overloaded function above instead.
 542              case 'getone':
 543              case 'getrow':
 544              case 'getall':
 545              case 'getcol':
 546              case 'getassoc':
 547              case 'selectlimit':
 548                  if ($this->isReadOnlyQuery(trim($args[0])) == true) {
 549                      $type = 'readonly';
 550                  }
 551                  break;
 552              case 'cachegetone':
 553              case 'cachegetrow':
 554              case 'cachegetall':
 555              case 'cachegetcol':
 556              case 'cachegetassoc':
 557              case 'cacheexecute':
 558              case 'cacheselect':
 559              case 'pageexecute':
 560              case 'cachepageexecute':
 561                  $type = 'readonly';
 562                  break;
 563                  // case 'ignoreerrors':
 564                  // 	 // When ignoreerrors is called, PIN to the connection until its called again.
 565                  // 	 if (!isset($args[0]) || (isset($args[0]) && $args[0] == FALSE)) {
 566                  // 	 	 $pin_connection = TRUE;
 567                  // 	 } else {
 568                  // 	 	 $pin_connection = FALSE;
 569                  // 	 }
 570                  // 	 break;
 571  
 572                  // Manual transactions
 573              case 'begintrans':
 574              case 'settransactionmode':
 575                      $pin_connection = true;
 576                  break;
 577              case 'rollbacktrans':
 578              case 'committrans':
 579                  $pin_connection = false;
 580                  break;
 581                  // Smart transactions
 582              case 'starttrans':
 583                  $pin_connection = true;
 584                  break;
 585              case 'completetrans':
 586              case 'failtrans':
 587                  // getConnection() will only unpin the transaction if we're exiting the last nested transaction
 588                  $pin_connection = false;
 589                  break;
 590  
 591              // Functions that don't require any connection and therefore
 592              // shouldn't force a connection be established before they run.
 593              case 'qstr':
 594              case 'escape':
 595              case 'binddate':
 596              case 'bindtimestamp':
 597              case 'setfetchmode':
 598                    $type = false; // No connection necessary.
 599                  break;
 600  
 601              // Default to assuming write connection is required to be on the safe side.
 602              default:
 603                  break;
 604          }
 605  
 606          if ($type === false) {
 607              if (is_array($this->connections) && count($this->connections) > 0) {
 608                  foreach ($this->connections as $key => $connection_obj) {
 609                      $adodb_obj = $connection_obj->getADOdbObject();
 610                      return call_user_func_array(array($adodb_obj, $method), $this->makeValuesReferenced($args)); // Just makes the function call on the first object.
 611                  }
 612              }
 613          } else {
 614                 $adodb_obj = $this->getConnection($type, $pin_connection);
 615              if (is_object($adodb_obj)) {
 616                  $result = call_user_func_array(array($adodb_obj, $method), $this->makeValuesReferenced($args));
 617  
 618                  return $result;
 619              }
 620          }
 621          return false;
 622      }
 623  
 624      /**
 625       * Magic method to proxy property getter calls back to the proper ADODB object currently in use.
 626       *
 627       * @param  $property
 628       * @return mixed
 629       * @throws Exception
 630       */
 631      public function __get($property)
 632      {
 633          if (is_array($this->connections) && count($this->connections) > 0) {
 634              foreach ($this->connections as $key => $connection_obj) {
 635                  // Just returns the property from the first object.
 636                  return $connection_obj->getADOdbObject()->$property;
 637              }
 638          }
 639  
 640          return false;
 641      }
 642  
 643      /**
 644       * Magic method to proxy property setter calls back to the proper ADODB object currently in use.
 645       *
 646       * @param  $property
 647       * @param  $value
 648       * @return mixed
 649       * @throws Exception
 650       */
 651      public function __set($property, $value)
 652      {
 653          // Special function to set object properties on all objects
 654          // without initiating a connection to the database.
 655          if (is_array($this->connections) && count($this->connections) > 0) {
 656              foreach ($this->connections as $key => $connection_obj) {
 657                  $connection_obj->getADOdbObject()->$property = $value;
 658              }
 659  
 660                 return true;
 661          }
 662  
 663          return false;
 664      }
 665  
 666      /**
 667       *  Override the __clone() magic method.
 668       */
 669      private function __clone()
 670      {
 671      }
 672  }
 673  
 674  /**
 675   * Class ADOdbLoadBalancerConnection
 676   */
 677  class ADOdbLoadBalancerConnection
 678  {
 679      /**
 680       * @var bool    ADOdb drive name.
 681       */
 682      protected $driver = false;
 683  
 684      /**
 685       * @var bool    ADODB object.
 686       */
 687      protected $adodb_obj = false;
 688  
 689      /**
 690       * @var string    Type of connection, either 'write' capable or 'readonly'
 691       */
 692      public $type = 'write';
 693  
 694      /**
 695       * @var int        Weight of connection, lower receives less queries, higher receives more queries.
 696       */
 697      public $weight = 1;
 698  
 699      /**
 700       * @var bool    Determines if the connection persistent.
 701       */
 702      public $persistent_connection = false;
 703  
 704      /**
 705       * @var string    Database connection host
 706       */
 707      public $host = '';
 708  
 709      /**
 710       * @var string    Database connection user
 711       */
 712      public $user = '';
 713  
 714      /**
 715       * @var string    Database connection password
 716       */
 717      public $password = '';
 718  
 719      /**
 720       * @var string    Database connection database name
 721       */
 722      public $database = '';
 723  
 724      /**
 725       * ADOdbLoadBalancerConnection constructor to setup the ADODB object.
 726       *
 727       * @param $driver
 728       * @param string $type
 729       * @param int    $weight
 730       * @param bool   $persistent_connection
 731       * @param string $argHostname
 732       * @param string $argUsername
 733       * @param string $argPassword
 734       * @param string $argDatabaseName
 735       */
 736      public function __construct(
 737          $driver,
 738          $type = 'write',
 739          $weight = 1,
 740          $persistent_connection = false,
 741          $argHostname = '',
 742          $argUsername = '',
 743          $argPassword = '',
 744          $argDatabaseName = ''
 745      ) {
 746          if ($type !== 'write' && $type !== 'readonly') {
 747              return false;
 748          }
 749  
 750          $this->adodb_obj = ADONewConnection($driver);
 751  
 752          $this->type = $type;
 753          $this->weight = $weight;
 754          $this->persistent_connection = $persistent_connection;
 755  
 756          $this->host = $argHostname;
 757          $this->user = $argUsername;
 758          $this->password = $argPassword;
 759          $this->database = $argDatabaseName;
 760  
 761          return true;
 762      }
 763  
 764      /**
 765       * Returns the ADODB object for this connection.
 766       *
 767       * @return bool
 768       */
 769      public function getADOdbObject()
 770      {
 771          return $this->adodb_obj;
 772      }
 773  }