$dsn, * 'username' => $username, * 'password' => $password, * ]); * $connection->open(); * ``` * * After the DB connection is established, one can execute SQL statements like the following: * * ```php * $command = $connection->createCommand('SELECT * FROM post'); * $posts = $command->queryAll(); * $command = $connection->createCommand('UPDATE post SET status=1'); * $command->execute(); * ``` * * One can also do prepared SQL execution and bind parameters to the prepared SQL. * When the parameters are coming from user input, you should use this approach * to prevent SQL injection attacks. The following is an example: * * ```php * $command = $connection->createCommand('SELECT * FROM post WHERE id=:id'); * $command->bindValue(':id', $_GET['id']); * $post = $command->query(); * ``` * * For more information about how to perform various DB queries, please refer to [[Command]]. * * If the underlying DBMS supports transactions, you can perform transactional SQL queries * like the following: * * ```php * $transaction = $connection->beginTransaction(); * try { * $connection->createCommand($sql1)->execute(); * $connection->createCommand($sql2)->execute(); * // ... executing other SQL statements ... * $transaction->commit(); * } catch (Exception $e) { * $transaction->rollBack(); * } * ``` * * You also can use shortcut for the above like the following: * * ```php * $connection->transaction(function () { * $order = new Order($customer); * $order->save(); * $order->addItems($items); * }); * ``` * * If needed you can pass transaction isolation level as a second parameter: * * ```php * $connection->transaction(function (Connection $db) { * //return $db->... * }, Transaction::READ_UNCOMMITTED); * ``` * * Connection is often used as an application component and configured in the application * configuration like the following: * * ```php * 'components' => [ * 'db' => [ * 'class' => '\yii\db\Connection', * 'dsn' => 'mysql:host=127.0.0.1;dbname=demo', * 'username' => 'root', * 'password' => '', * 'charset' => 'utf8', * ], * ], * ``` * * @property string $driverName Name of the DB driver. * @property boolean $isActive Whether the DB connection is established. This property is read-only. * @property string $lastInsertID The row ID of the last row inserted, or the last value retrieved from the * sequence object. This property is read-only. * @property PDO $masterPdo The PDO instance for the currently active master connection. This property is * read-only. * @property QueryBuilder $queryBuilder The query builder for the current DB connection. This property is * read-only. * @property Schema $schema The schema information for the database opened by this connection. This property * is read-only. * @property Connection $slave The currently active slave connection. Null is returned if there is slave * available and `$fallbackToMaster` is false. This property is read-only. * @property PDO $slavePdo The PDO instance for the currently active slave connection. Null is returned if no * slave connection is available and `$fallbackToMaster` is false. This property is read-only. * @property Transaction $transaction The currently active transaction. Null if no active transaction. This * property is read-only. * * @author Qiang Xue * @since 2.0 */ class Connection extends Component { /** * @event Event an event that is triggered after a DB connection is established */ const EVENT_AFTER_OPEN = 'afterOpen'; /** * @event Event an event that is triggered right before a top-level transaction is started */ const EVENT_BEGIN_TRANSACTION = 'beginTransaction'; /** * @event Event an event that is triggered right after a top-level transaction is committed */ const EVENT_COMMIT_TRANSACTION = 'commitTransaction'; /** * @event Event an event that is triggered right after a top-level transaction is rolled back */ const EVENT_ROLLBACK_TRANSACTION = 'rollbackTransaction'; /** * @var string the Data Source Name, or DSN, contains the information required to connect to the database. * Please refer to the [PHP manual](http://www.php.net/manual/en/function.PDO-construct.php) on * the format of the DSN string. * * For [SQLite](http://php.net/manual/en/ref.pdo-sqlite.connection.php) you may use a path alias * for specifying the database path, e.g. `sqlite:@app/data/db.sql`. * * @see charset */ public $dsn; /** * @var string the username for establishing DB connection. Defaults to `null` meaning no username to use. */ public $username; /** * @var string the password for establishing DB connection. Defaults to `null` meaning no password to use. */ public $password; /** * @var array PDO attributes (name => value) that should be set when calling [[open()]] * to establish a DB connection. Please refer to the * [PHP manual](http://www.php.net/manual/en/function.PDO-setAttribute.php) for * details about available attributes. */ public $attributes; /** * @var PDO the PHP PDO instance associated with this DB connection. * This property is mainly managed by [[open()]] and [[close()]] methods. * When a DB connection is active, this property will represent a PDO instance; * otherwise, it will be null. * @see pdoClass */ public $pdo; /** * @var boolean whether to enable schema caching. * Note that in order to enable truly schema caching, a valid cache component as specified * by [[schemaCache]] must be enabled and [[enableSchemaCache]] must be set true. * @see schemaCacheDuration * @see schemaCacheExclude * @see schemaCache */ public $enableSchemaCache = false; /** * @var integer number of seconds that table metadata can remain valid in cache. * Use 0 to indicate that the cached data will never expire. * @see enableSchemaCache */ public $schemaCacheDuration = 3600; /** * @var array list of tables whose metadata should NOT be cached. Defaults to empty array. * The table names may contain schema prefix, if any. Do not quote the table names. * @see enableSchemaCache */ public $schemaCacheExclude = []; /** * @var Cache|string the cache object or the ID of the cache application component that * is used to cache the table metadata. * @see enableSchemaCache */ public $schemaCache = 'cache'; /** * @var boolean whether to enable query caching. * Note that in order to enable query caching, a valid cache component as specified * by [[queryCache]] must be enabled and [[enableQueryCache]] must be set true. * Also, only the results of the queries enclosed within [[cache()]] will be cached. * @see queryCache * @see cache() * @see noCache() */ public $enableQueryCache = true; /** * @var integer the default number of seconds that query results can remain valid in cache. * Use 0 to indicate that the cached data will never expire. * Defaults to 3600, meaning 3600 seconds, or one hour. Use 0 to indicate that the cached data will never expire. * The value of this property will be used when [[cache()]] is called without a cache duration. * @see enableQueryCache * @see cache() */ public $queryCacheDuration = 3600; /** * @var Cache|string the cache object or the ID of the cache application component * that is used for query caching. * @see enableQueryCache */ public $queryCache = 'cache'; /** * @var string the charset used for database connection. The property is only used * for MySQL, PostgreSQL and CUBRID databases. Defaults to null, meaning using default charset * as configured by the database. * * For Oracle Database, the charset must be specified in the [[dsn]], for example for UTF-8 by appending `;charset=UTF-8` * to the DSN string. * * The same applies for if you're using GBK or BIG5 charset with MySQL, then it's highly recommended to * specify charset via [[dsn]] like `'mysql:dbname=mydatabase;host=127.0.0.1;charset=GBK;'`. */ public $charset; /** * @var boolean whether to turn on prepare emulation. Defaults to false, meaning PDO * will use the native prepare support if available. For some databases (such as MySQL), * this may need to be set true so that PDO can emulate the prepare support to bypass * the buggy native prepare support. * The default value is null, which means the PDO ATTR_EMULATE_PREPARES value will not be changed. */ public $emulatePrepare; /** * @var string the common prefix or suffix for table names. If a table name is given * as `{{%TableName}}`, then the percentage character `%` will be replaced with this * property value. For example, `{{%post}}` becomes `{{tbl_post}}`. */ public $tablePrefix = ''; /** * @var array mapping between PDO driver names and [[Schema]] classes. * The keys of the array are PDO driver names while the values the corresponding * schema class name or configuration. Please refer to [[Yii::createObject()]] for * details on how to specify a configuration. * * This property is mainly used by [[getSchema()]] when fetching the database schema information. * You normally do not need to set this property unless you want to use your own * [[Schema]] class to support DBMS that is not supported by Yii. */ public $schemaMap = [ 'pgsql' => 'yii\db\pgsql\Schema', // PostgreSQL 'mysqli' => 'yii\db\mysql\Schema', // MySQL 'mysql' => 'yii\db\mysql\Schema', // MySQL 'sqlite' => 'yii\db\sqlite\Schema', // sqlite 3 'sqlite2' => 'yii\db\sqlite\Schema', // sqlite 2 'sqlsrv' => 'yii\db\mssql\Schema', // newer MSSQL driver on MS Windows hosts 'oci' => 'yii\db\oci\Schema', // Oracle driver 'mssql' => 'yii\db\mssql\Schema', // older MSSQL driver on MS Windows hosts 'dblib' => 'yii\db\mssql\Schema', // dblib drivers on GNU/Linux (and maybe other OSes) hosts 'cubrid' => 'yii\db\cubrid\Schema', // CUBRID ]; /** * @var string Custom PDO wrapper class. If not set, it will use [[PDO]] or [[yii\db\mssql\PDO]] when MSSQL is used. * @see pdo */ public $pdoClass; /** * @var string the class used to create new database [[Command]] objects. If you want to extend the [[Command]] class, * you may configure this property to use your extended version of the class. * @see createCommand * @since 2.0.7 */ public $commandClass = 'yii\db\Command'; /** * @var boolean whether to enable [savepoint](http://en.wikipedia.org/wiki/Savepoint). * Note that if the underlying DBMS does not support savepoint, setting this property to be true will have no effect. */ public $enableSavepoint = true; /** * @var Cache|string the cache object or the ID of the cache application component that is used to store * the health status of the DB servers specified in [[masters]] and [[slaves]]. * This is used only when read/write splitting is enabled or [[masters]] is not empty. */ public $serverStatusCache = 'cache'; /** * @var integer the retry interval in seconds for dead servers listed in [[masters]] and [[slaves]]. * This is used together with [[serverStatusCache]]. */ public $serverRetryInterval = 600; /** * @var boolean whether to enable read/write splitting by using [[slaves]] to read data. * Note that if [[slaves]] is empty, read/write splitting will NOT be enabled no matter what value this property takes. */ public $enableSlaves = true; /** * @var array list of slave connection configurations. Each configuration is used to create a slave DB connection. * When [[enableSlaves]] is true, one of these configurations will be chosen and used to create a DB connection * for performing read queries only. * @see enableSlaves * @see slaveConfig */ public $slaves = []; /** * @var array the configuration that should be merged with every slave configuration listed in [[slaves]]. * For example, * * ```php * [ * 'username' => 'slave', * 'password' => 'slave', * 'attributes' => [ * // use a smaller connection timeout * PDO::ATTR_TIMEOUT => 10, * ], * ] * ``` */ public $slaveConfig = []; /** * @var array list of master connection configurations. Each configuration is used to create a master DB connection. * When [[open()]] is called, one of these configurations will be chosen and used to create a DB connection * which will be used by this object. * Note that when this property is not empty, the connection setting (e.g. "dsn", "username") of this object will * be ignored. * @see masterConfig */ public $masters = []; /** * @var array the configuration that should be merged with every master configuration listed in [[masters]]. * For example, * * ```php * [ * 'username' => 'master', * 'password' => 'master', * 'attributes' => [ * // use a smaller connection timeout * PDO::ATTR_TIMEOUT => 10, * ], * ] * ``` */ public $masterConfig = []; /** * @var Transaction the currently active transaction */ private $_transaction; /** * @var Schema the database schema */ private $_schema; /** * @var string driver name */ private $_driverName; /** * @var Connection the currently active slave connection */ private $_slave = false; /** * @var array query cache parameters for the [[cache()]] calls */ private $_queryCacheInfo = []; /** * Returns a value indicating whether the DB connection is established. * @return boolean whether the DB connection is established */ public function getIsActive() { return $this->pdo !== null; } /** * Uses query cache for the queries performed with the callable. * When query caching is enabled ([[enableQueryCache]] is true and [[queryCache]] refers to a valid cache), * queries performed within the callable will be cached and their results will be fetched from cache if available. * For example, * * ```php * // The customer will be fetched from cache if available. * // If not, the query will be made against DB and cached for use next time. * $customer = $db->cache(function (Connection $db) { * return $db->createCommand('SELECT * FROM customer WHERE id=1')->queryOne(); * }); * ``` * * Note that query cache is only meaningful for queries that return results. For queries performed with * [[Command::execute()]], query cache will not be used. * * @param callable $callable a PHP callable that contains DB queries which will make use of query cache. * The signature of the callable is `function (Connection $db)`. * @param integer $duration the number of seconds that query results can remain valid in the cache. If this is * not set, the value of [[queryCacheDuration]] will be used instead. * Use 0 to indicate that the cached data will never expire. * @param \yii\caching\Dependency $dependency the cache dependency associated with the cached query results. * @return mixed the return result of the callable * @throws \Exception if there is any exception during query * @see enableQueryCache * @see queryCache * @see noCache() */ public function cache(callable $callable, $duration = null, $dependency = null) { $this->_queryCacheInfo[] = [$duration === null ? $this->queryCacheDuration : $duration, $dependency]; try { $result = call_user_func($callable, $this); array_pop($this->_queryCacheInfo); return $result; } catch (\Exception $e) { array_pop($this->_queryCacheInfo); throw $e; } } /** * Disables query cache temporarily. * Queries performed within the callable will not use query cache at all. For example, * * ```php * $db->cache(function (Connection $db) { * * // ... queries that use query cache ... * * return $db->noCache(function (Connection $db) { * // this query will not use query cache * return $db->createCommand('SELECT * FROM customer WHERE id=1')->queryOne(); * }); * }); * ``` * * @param callable $callable a PHP callable that contains DB queries which should not use query cache. * The signature of the callable is `function (Connection $db)`. * @return mixed the return result of the callable * @throws \Exception if there is any exception during query * @see enableQueryCache * @see queryCache * @see cache() */ public function noCache(callable $callable) { $this->_queryCacheInfo[] = false; try { $result = call_user_func($callable, $this); array_pop($this->_queryCacheInfo); return $result; } catch (\Exception $e) { array_pop($this->_queryCacheInfo); throw $e; } } /** * Returns the current query cache information. * This method is used internally by [[Command]]. * @param integer $duration the preferred caching duration. If null, it will be ignored. * @param \yii\caching\Dependency $dependency the preferred caching dependency. If null, it will be ignored. * @return array the current query cache information, or null if query cache is not enabled. * @internal */ public function getQueryCacheInfo($duration, $dependency) { if (!$this->enableQueryCache) { return null; } $info = end($this->_queryCacheInfo); if (is_array($info)) { if ($duration === null) { $duration = $info[0]; } if ($dependency === null) { $dependency = $info[1]; } } if ($duration === 0 || $duration > 0) { if (is_string($this->queryCache) && Yii::$app) { $cache = Yii::$app->get($this->queryCache, false); } else { $cache = $this->queryCache; } if ($cache instanceof Cache) { return [$cache, $duration, $dependency]; } } return null; } /** * Establishes a DB connection. * It does nothing if a DB connection has already been established. * @throws Exception if connection fails */ public function open() { if ($this->pdo !== null) { return; } if (!empty($this->masters)) { $db = $this->openFromPool($this->masters, $this->masterConfig); if ($db !== null) { $this->pdo = $db->pdo; return; } else { throw new InvalidConfigException('None of the master DB servers is available.'); } } if (empty($this->dsn)) { throw new InvalidConfigException('Connection::dsn cannot be empty.'); } $token = 'Opening DB connection: ' . $this->dsn; try { Yii::info($token, __METHOD__); Yii::beginProfile($token, __METHOD__); $this->pdo = $this->createPdoInstance(); $this->initConnection(); Yii::endProfile($token, __METHOD__); } catch (\PDOException $e) { Yii::endProfile($token, __METHOD__); throw new Exception($e->getMessage(), $e->errorInfo, (int) $e->getCode(), $e); } } /** * Closes the currently active DB connection. * It does nothing if the connection is already closed. */ public function close() { if ($this->pdo !== null) { Yii::trace('Closing DB connection: ' . $this->dsn, __METHOD__); $this->pdo = null; $this->_schema = null; $this->_transaction = null; } if ($this->_slave) { $this->_slave->close(); $this->_slave = null; } } /** * Creates the PDO instance. * This method is called by [[open]] to establish a DB connection. * The default implementation will create a PHP PDO instance. * You may override this method if the default PDO needs to be adapted for certain DBMS. * @return PDO the pdo instance */ protected function createPdoInstance() { $pdoClass = $this->pdoClass; if ($pdoClass === null) { $pdoClass = 'PDO'; if ($this->_driverName !== null) { $driver = $this->_driverName; } elseif (($pos = strpos($this->dsn, ':')) !== false) { $driver = strtolower(substr($this->dsn, 0, $pos)); } if (isset($driver)) { if ($driver === 'mssql' || $driver === 'dblib') { $pdoClass = 'yii\db\mssql\PDO'; } elseif ($driver === 'sqlsrv') { $pdoClass = 'yii\db\mssql\SqlsrvPDO'; } } } $dsn = $this->dsn; if (strncmp('sqlite:@', $dsn, 8) === 0) { $dsn = 'sqlite:' . Yii::getAlias(substr($dsn, 7)); } return new $pdoClass($dsn, $this->username, $this->password, $this->attributes); } /** * Initializes the DB connection. * This method is invoked right after the DB connection is established. * The default implementation turns on `PDO::ATTR_EMULATE_PREPARES` * if [[emulatePrepare]] is true, and sets the database [[charset]] if it is not empty. * It then triggers an [[EVENT_AFTER_OPEN]] event. */ protected function initConnection() { $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); if ($this->emulatePrepare !== null && constant('PDO::ATTR_EMULATE_PREPARES')) { $this->pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, $this->emulatePrepare); } if ($this->charset !== null && in_array($this->getDriverName(), ['pgsql', 'mysql', 'mysqli', 'cubrid'], true)) { $this->pdo->exec('SET NAMES ' . $this->pdo->quote($this->charset)); } $this->trigger(self::EVENT_AFTER_OPEN); } /** * Creates a command for execution. * @param string $sql the SQL statement to be executed * @param array $params the parameters to be bound to the SQL statement * @return Command the DB command */ public function createCommand($sql = null, $params = []) { /** @var Command $command */ $command = new $this->commandClass([ 'db' => $this, 'sql' => $sql, ]); return $command->bindValues($params); } /** * Returns the currently active transaction. * @return Transaction the currently active transaction. Null if no active transaction. */ public function getTransaction() { return $this->_transaction && $this->_transaction->getIsActive() ? $this->_transaction : null; } /** * Starts a transaction. * @param string|null $isolationLevel The isolation level to use for this transaction. * See [[Transaction::begin()]] for details. * @return Transaction the transaction initiated */ public function beginTransaction($isolationLevel = null) { $this->open(); if (($transaction = $this->getTransaction()) === null) { $transaction = $this->_transaction = new Transaction(['db' => $this]); } $transaction->begin($isolationLevel); return $transaction; } /** * Executes callback provided in a transaction. * * @param callable $callback a valid PHP callback that performs the job. Accepts connection instance as parameter. * @param string|null $isolationLevel The isolation level to use for this transaction. * See [[Transaction::begin()]] for details. * @throws \Exception * @return mixed result of callback function */ public function transaction(callable $callback, $isolationLevel = null) { $transaction = $this->beginTransaction($isolationLevel); $level = $transaction->level; try { $result = call_user_func($callback, $this); if ($transaction->isActive && $transaction->level === $level) { $transaction->commit(); } } catch (\Exception $e) { if ($transaction->isActive && $transaction->level === $level) { $transaction->rollBack(); } throw $e; } return $result; } /** * Returns the schema information for the database opened by this connection. * @return Schema the schema information for the database opened by this connection. * @throws NotSupportedException if there is no support for the current driver type */ public function getSchema() { if ($this->_schema !== null) { return $this->_schema; } else { $driver = $this->getDriverName(); if (isset($this->schemaMap[$driver])) { $config = !is_array($this->schemaMap[$driver]) ? ['class' => $this->schemaMap[$driver]] : $this->schemaMap[$driver]; $config['db'] = $this; return $this->_schema = Yii::createObject($config); } else { throw new NotSupportedException("Connection does not support reading schema information for '$driver' DBMS."); } } } /** * Returns the query builder for the current DB connection. * @return QueryBuilder the query builder for the current DB connection. */ public function getQueryBuilder() { return $this->getSchema()->getQueryBuilder(); } /** * Obtains the schema information for the named table. * @param string $name table name. * @param boolean $refresh whether to reload the table schema even if it is found in the cache. * @return TableSchema table schema information. Null if the named table does not exist. */ public function getTableSchema($name, $refresh = false) { return $this->getSchema()->getTableSchema($name, $refresh); } /** * Returns the ID of the last inserted row or sequence value. * @param string $sequenceName name of the sequence object (required by some DBMS) * @return string the row ID of the last row inserted, or the last value retrieved from the sequence object * @see http://www.php.net/manual/en/function.PDO-lastInsertId.php */ public function getLastInsertID($sequenceName = '') { return $this->getSchema()->getLastInsertID($sequenceName); } /** * Quotes a string value for use in a query. * Note that if the parameter is not a string, it will be returned without change. * @param string $value string to be quoted * @return string the properly quoted string * @see http://www.php.net/manual/en/function.PDO-quote.php */ public function quoteValue($value) { return $this->getSchema()->quoteValue($value); } /** * Quotes a table name for use in a query. * If the table name contains schema prefix, the prefix will also be properly quoted. * If the table name is already quoted or contains special characters including '(', '[[' and '{{', * then this method will do nothing. * @param string $name table name * @return string the properly quoted table name */ public function quoteTableName($name) { return $this->getSchema()->quoteTableName($name); } /** * Quotes a column name for use in a query. * If the column name contains prefix, the prefix will also be properly quoted. * If the column name is already quoted or contains special characters including '(', '[[' and '{{', * then this method will do nothing. * @param string $name column name * @return string the properly quoted column name */ public function quoteColumnName($name) { return $this->getSchema()->quoteColumnName($name); } /** * Processes a SQL statement by quoting table and column names that are enclosed within double brackets. * Tokens enclosed within double curly brackets are treated as table names, while * tokens enclosed within double square brackets are column names. They will be quoted accordingly. * Also, the percentage character "%" at the beginning or ending of a table name will be replaced * with [[tablePrefix]]. * @param string $sql the SQL to be quoted * @return string the quoted SQL */ public function quoteSql($sql) { return preg_replace_callback( '/(\\{\\{(%?[\w\-\. ]+%?)\\}\\}|\\[\\[([\w\-\. ]+)\\]\\])/', function ($matches) { if (isset($matches[3])) { return $this->quoteColumnName($matches[3]); } else { return str_replace('%', $this->tablePrefix, $this->quoteTableName($matches[2])); } }, $sql ); } /** * Returns the name of the DB driver. Based on the the current [[dsn]], in case it was not set explicitly * by an end user. * @return string name of the DB driver */ public function getDriverName() { if ($this->_driverName === null) { if (($pos = strpos($this->dsn, ':')) !== false) { $this->_driverName = strtolower(substr($this->dsn, 0, $pos)); } else { $this->_driverName = strtolower($this->getSlavePdo()->getAttribute(PDO::ATTR_DRIVER_NAME)); } } return $this->_driverName; } /** * Changes the current driver name. * @param string $driverName name of the DB driver */ public function setDriverName($driverName) { $this->_driverName = strtolower($driverName); } /** * Returns the PDO instance for the currently active slave connection. * When [[enableSlaves]] is true, one of the slaves will be used for read queries, and its PDO instance * will be returned by this method. * @param boolean $fallbackToMaster whether to return a master PDO in case none of the slave connections is available. * @return PDO the PDO instance for the currently active slave connection. Null is returned if no slave connection * is available and `$fallbackToMaster` is false. */ public function getSlavePdo($fallbackToMaster = true) { $db = $this->getSlave(false); if ($db === null) { return $fallbackToMaster ? $this->getMasterPdo() : null; } else { return $db->pdo; } } /** * Returns the PDO instance for the currently active master connection. * This method will open the master DB connection and then return [[pdo]]. * @return PDO the PDO instance for the currently active master connection. */ public function getMasterPdo() { $this->open(); return $this->pdo; } /** * Returns the currently active slave connection. * If this method is called the first time, it will try to open a slave connection when [[enableSlaves]] is true. * @param boolean $fallbackToMaster whether to return a master connection in case there is no slave connection available. * @return Connection the currently active slave connection. Null is returned if there is slave available and * `$fallbackToMaster` is false. */ public function getSlave($fallbackToMaster = true) { if (!$this->enableSlaves) { return $fallbackToMaster ? $this : null; } if ($this->_slave === false) { $this->_slave = $this->openFromPool($this->slaves, $this->slaveConfig); } return $this->_slave === null && $fallbackToMaster ? $this : $this->_slave; } /** * Executes the provided callback by using the master connection. * * This method is provided so that you can temporarily force using the master connection to perform * DB operations even if they are read queries. For example, * * ```php * $result = $db->useMaster(function ($db) { * return $db->createCommand('SELECT * FROM user LIMIT 1')->queryOne(); * }); * ``` * * @param callable $callback a PHP callable to be executed by this method. Its signature is * `function (Connection $db)`. Its return value will be returned by this method. * @return mixed the return value of the callback */ public function useMaster(callable $callback) { $enableSlave = $this->enableSlaves; $this->enableSlaves = false; $result = call_user_func($callback, $this); $this->enableSlaves = $enableSlave; return $result; } /** * Opens the connection to a server in the pool. * This method implements the load balancing among the given list of the servers. * @param array $pool the list of connection configurations in the server pool * @param array $sharedConfig the configuration common to those given in `$pool`. * @return Connection the opened DB connection, or null if no server is available * @throws InvalidConfigException if a configuration does not specify "dsn" */ protected function openFromPool(array $pool, array $sharedConfig) { if (empty($pool)) { return null; } if (!isset($sharedConfig['class'])) { $sharedConfig['class'] = get_class($this); } $cache = is_string($this->serverStatusCache) ? Yii::$app->get($this->serverStatusCache, false) : $this->serverStatusCache; shuffle($pool); foreach ($pool as $config) { $config = array_merge($sharedConfig, $config); if (empty($config['dsn'])) { throw new InvalidConfigException('The "dsn" option must be specified.'); } $key = [__METHOD__, $config['dsn']]; if ($cache instanceof Cache && $cache->get($key)) { // should not try this dead server now continue; } /* @var $db Connection */ $db = Yii::createObject($config); try { $db->open(); return $db; } catch (\Exception $e) { Yii::warning("Connection ({$config['dsn']}) failed: " . $e->getMessage(), __METHOD__); if ($cache instanceof Cache) { // mark this server as dead and only retry it after the specified interval $cache->set($key, 1, $this->serverRetryInterval); } } } return null; } /** * Close the connection before serializing. * @return array */ public function __sleep() { $this->close(); return array_keys((array) $this); } }