Deprecate master/slave terminology

Closes doctrine#4052

lib/Doctrine/DBAL/Connections/MasterSlaveConnection.php

@@ -53,6 +53,8 @@
  *
  * Instantiation through the DriverManager looks like:
  *
+ * @deprecated use PrimaryReplicaConnection instead
+ *
  * @example
  *
  * $conn = DriverManager::getConnection(array(

lib/Doctrine/DBAL/Connections/PrimaryReplicaConnection.php

@@ -0,0 +1,359 @@
+<?php
+
+namespace Doctrine\DBAL\Connections;
+
+use Doctrine\Common\EventManager;
+use Doctrine\DBAL\Configuration;
+use Doctrine\DBAL\Connection;
+use Doctrine\DBAL\Driver;
+use Doctrine\DBAL\Driver\Connection as DriverConnection;
+use Doctrine\DBAL\Driver\Statement;
+use Doctrine\DBAL\Event\ConnectionEventArgs;
+use Doctrine\DBAL\Events;
+use InvalidArgumentException;
+
+use function array_rand;
+use function assert;
+use function count;
+use function func_get_args;
+
+/**
+ * Primary-Replica Connection
+ *
+ * Connection can be used with primary-replica setups.
+ *
+ * Important for the understanding of this connection should be how and when
+ * it picks the replica or primary.
+ *
+ * 1. Replica if primary was never picked before and ONLY if 'getWrappedConnection'
+ *    or 'executeQuery' is used.
+ * 2. Primary picked when 'exec', 'executeUpdate', 'insert', 'delete', 'update', 'createSavepoint',
+ *    'releaseSavepoint', 'beginTransaction', 'rollback', 'commit', 'query' or
+ *    'prepare' is called.
+ * 3. If Primary was picked once during the lifetime of the connection it will always get picked afterwards.
+ * 4. One replica connection is randomly picked ONCE during a request.
+ *
+ * ATTENTION: You can write to the replica with this connection if you execute a write query without
+ * opening up a transaction. For example:
+ *
+ *      $conn = DriverManager::getConnection(...);
+ *      $conn->executeQuery("DELETE FROM table");
+ *
+ * Be aware that Connection#executeQuery is a method specifically for READ
+ * operations only.
+ *
+ * This connection is limited to replica operations using the
+ * Connection#executeQuery operation only, because it wouldn't be compatible
+ * with the ORM or SchemaManager code otherwise. Both use all the other
+ * operations in a context where writes could happen to a replica, which makes
+ * this restricted approach necessary.
+ *
+ * You can manually connect to the primary at any time by calling:
+ *
+ *      $conn->connect('primary');
+ *
+ * Instantiation through the DriverManager looks like:
+ *
+ * @example
+ *
+ * $conn = DriverManager::getConnection(array(
+ *    'wrapperClass' => 'Doctrine\DBAL\Connections\PrimaryReplicaConnection',
+ *    'driver' => 'pdo_mysql',
+ *    'primary' => array('user' => '', 'password' => '', 'host' => '', 'dbname' => ''),
+ *    'replica' => array(
+ *        array('user' => 'replica1', 'password', 'host' => '', 'dbname' => ''),
+ *        array('user' => 'replica2', 'password', 'host' => '', 'dbname' => ''),
+ *    )
+ * ));
+ *
+ * You can also pass 'driverOptions' and any other documented option to each of this drivers to pass additional information.
+ */
+final class PrimaryReplicaConnection extends Connection
+{
+    /**
+     * Primary and Replica connection (one of the randomly picked replicas).
+     *
+     * @var DriverConnection[]|null[]
+     */
+    private $connections = ['primary' => null, 'replica' => null];
+
+    /**
+     * You can keep the replica connection and then switch back to it
+     * during the request if you know what you are doing.
+     *
+     * @var bool
+     */
+    private $keepReplica = false;
+
+    /**
+     * Creates Primary Replica Connection.
+     *
+     * @param mixed[] $params
+     *
+     * @throws InvalidArgumentException
+     */
+    public function __construct(
+        array $params,
+        Driver $driver,
+        ?Configuration $config = null,
+        ?EventManager $eventManager = null
+    ) {
+        if (! isset($params['replica'], $params['primary'])) {
+            throw new InvalidArgumentException('primary or replica configuration missing');
+        }
+
+        if (count($params['replica']) === 0) {
+            throw new InvalidArgumentException('You have to configure at least one replica.');
+        }
+
+        $params['primary']['driver'] = $params['driver'];
+        foreach ($params['replica'] as $replicaKey => $replica) {
+            $params['replica'][$replicaKey]['driver'] = $params['driver'];
+        }
+
+        $this->keepReplica = (bool) ($params['keepReplica'] ?? false);
+
+        parent::__construct($params, $driver, $config, $eventManager);
+    }
+
+    /**
+     * Checks if the connection is currently towards the primary or not.
+     */
+    public function isConnectedToPrimary(): bool
+    {
+        return $this->_conn !== null && $this->_conn === $this->connections['primary'];
+    }
+
+    public function connect(?string $connectionName = null): bool
+    {
+        $requestedConnectionChange = ($connectionName !== null);
+        $connectionName            = $connectionName ?: 'replica';
+
+        if ($connectionName !== 'replica' && $connectionName !== 'primary') {
+            throw new InvalidArgumentException('Invalid option to connect(), only primary or replica allowed.');
+        }
+
+        // If we have a connection open, and this is not an explicit connection
+        // change request, then abort right here, because we are already done.
+        // This prevents writes to the replica in case of "keepReplica" option enabled.
+        if ($this->_conn !== null && ! $requestedConnectionChange) {
+            return false;
+        }
+
+        $forcePrimaryAsReplica = false;
+
+        if ($this->getTransactionNestingLevel() > 0) {
+            $connectionName        = 'primary';
+            $forcePrimaryAsReplica = true;
+        }
+
+        if (isset($this->connections[$connectionName])) {
+            $this->_conn = $this->connections[$connectionName];
+
+            if ($forcePrimaryAsReplica && ! $this->keepReplica) {
+                $this->connections['replica'] = $this->_conn;
+            }
+
+            return false;
+        }
+
+        if ($connectionName === 'primary') {
+            $this->connections['primary'] = $this->_conn = $this->connectTo($connectionName);
+
+            // Set replica connection to primary to avoid invalid reads
+            if (! $this->keepReplica) {
+                $this->connections['replica'] = $this->connections['primary'];
+            }
+        } else {
+            $this->connections['replica'] = $this->_conn = $this->connectTo($connectionName);
+        }
+
+        if ($this->_eventManager->hasListeners(Events::postConnect)) {
+            $eventArgs = new ConnectionEventArgs($this);
+            $this->_eventManager->dispatchEvent(Events::postConnect, $eventArgs);
+        }
+
+        return true;
+    }
+
+    /**
+     * Connects to a specific connection.
+     */
+    private function connectTo(string $connectionName): DriverConnection
+    {
+        $params = $this->getParams();
+
+        $driverOptions = $params['driverOptions'] ?? [];
+
+        $connectionParams = $this->chooseConnectionConfiguration($connectionName, $params);
+
+        $user     = $connectionParams['user'] ?? null;
+        $password = $connectionParams['password'] ?? null;
+
+        return $this->_driver->connect($connectionParams, $user, $password, $driverOptions);
+    }
+
+    /**
+     * @param mixed[] $params
+     *
+     * @return mixed[]
+     */
+    private function chooseConnectionConfiguration(string $connectionName, array $params): array
+    {
+        if ($connectionName === 'primary') {
+            return $params['primary'];
+        }
+
+        $config = $params['replica'][array_rand($params['replica'])];
+
+        if (! isset($config['charset']) && isset($params['primary']['charset'])) {
+            $config['charset'] = $params['primary']['charset'];
+        }
+
+        return $config;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function executeUpdate($query, array $params = [], array $types = []): int
+    {
+        $this->connect('primary');
+
+        return parent::executeUpdate($query, $params, $types);
+    }
+
+    public function beginTransaction(): bool
+    {
+        $this->connect('primary');
+
+        return parent::beginTransaction();
+    }
+
+    public function commit(): bool
+    {
+        $this->connect('primary');
+
+        return parent::commit();
+    }
+
+    public function rollBack(): bool
+    {
+        $this->connect('primary');
+
+        return parent::rollBack();
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function delete($tableName, array $identifier, array $types = []): int
+    {
+        $this->connect('primary');
+
+        return parent::delete($tableName, $identifier, $types);
+    }
+
+    public function close(): void
+    {
+        unset($this->connections['primary'], $this->connections['replica']);
+
+        parent::close();
+
+        $this->_conn       = null;
+        $this->connections = ['primary' => null, 'replica' => null];
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function update($tableName, array $data, array $identifier, array $types = []): int
+    {
+        $this->connect('primary');
+
+        return parent::update($tableName, $data, $identifier, $types);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function insert($tableName, array $data, array $types = []): int
+    {
+        $this->connect('primary');
+
+        return parent::insert($tableName, $data, $types);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function exec($statement): int
+    {
+        $this->connect('primary');
+
+        return parent::exec($statement);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function createSavepoint($savepoint): void
+    {
+        $this->connect('primary');
+
+        parent::createSavepoint($savepoint);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function releaseSavepoint($savepoint): void
+    {
+        $this->connect('primary');
+
+        parent::releaseSavepoint($savepoint);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function rollbackSavepoint($savepoint): void
+    {
+        $this->connect('primary');
+
+        parent::rollbackSavepoint($savepoint);
+    }
+
+    public function query(): Statement
+    {
+        $this->connect('primary');
+        assert($this->_conn instanceof DriverConnection);
+
+        $args = func_get_args();
+
+        $logger = $this->getConfiguration()->getSQLLogger();
+        if ($logger) {
+            $logger->startQuery($args[0]);
+        }
+
+        $statement = $this->_conn->query(...$args);
+
+        $statement->setFetchMode($this->defaultFetchMode);
+
+        if ($logger) {
+            $logger->stopQuery();
+        }
+
+        return $statement;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function prepare($statement): Statement
+    {
+        $this->connect('primary');
+
+        return parent::prepare($statement);
+    }
+}

lib/Doctrine/DBAL/DriverManager.php

@@ -142,17 +142,29 @@ public static function getConnection(
 
         $params = self::parseDatabaseUrl($params);
 
-        // URL support for MasterSlaveConnection
+        // @todo: deprecated, notice thrown by connection constructor
         if (isset($params['master'])) {
             $params['master'] = self::parseDatabaseUrl($params['master']);
         }
 
+        // @todo: deprecated, notice thrown by connection constructor
         if (isset($params['slaves'])) {
             foreach ($params['slaves'] as $key => $slaveParams) {
                 $params['slaves'][$key] = self::parseDatabaseUrl($slaveParams);
             }
         }
 
+        // URL support for PrimaryReplicaConnection
+        if (isset($params['primary'])) {
+            $params['primary'] = self::parseDatabaseUrl($params['primary']);
+        }
+
+        if (isset($params['replica'])) {
+            foreach ($params['replica'] as $key => $replicaParams) {
+                $params['replica'][$key] = self::parseDatabaseUrl($replicaParams);
+            }
+        }
+
         // URL support for PoolingShardConnection
         if (isset($params['global'])) {
             $params['global'] = self::parseDatabaseUrl($params['global']);