Automatically retry queries on database connections that have 'gone a…

…way'.

src/Illuminate/Database/Connection.php

@@ -22,6 +22,13 @@ class Connection implements ConnectionInterface {
 	 */
 	protected $readPdo;
 
+	/**
+	 * The reconnector instance for the connection.
+	 *
+	 * @var callable
+	 */
+	protected $reconnector;
+
 	/**
 	 * The query grammar implementation.
 	 *
@@ -537,8 +544,46 @@ public function pretend(Closure $callback)
 	 */
 	protected function run($query, $bindings, Closure $callback)
 	{
+		$this->reconnectIfMissingConnection();
+
 		$start = microtime(true);
 
+		// Here we will run this query. If an exception occurs we'll determine if it was
+		// caused by a connection that has been lost. If that is the cause, we'll try
+		// to re-establish connection and re-run the query with a fresh connection.
+		try
+		{
+			$result = $this->runQueryCallback($query, $bindings, $callback);
+		}
+		catch (QueryException $e)
+		{
+			$result = $this->tryAgainIfCausedByLostConnection(
+				$e, $query, $bindings, $callback
+			);
+		}
+
+		// Once we have run the query we will calculate the time that it took to run and
+		// then log the query, bindings, and execution time so we will report them on
+		// the event that the developer needs them. We'll log time in milliseconds.
+		$time = $this->getElapsedTime($start);
+
+		$this->logQuery($query, $bindings, $time);
+
+		return $result;
+	}
+
+	/**
+	 * Run a SQL statement.
+	 *
+	 * @param  string    $query
+	 * @param  array     $bindings
+	 * @param  \Closure  $callback
+	 * @return mixed
+	 *
+	 * @throws QueryException
+	 */
+	protected function runQueryCallback($query, $bindings, Closure $callback)
+	{
 		// To execute the statement, we'll simply call the callback, which will actually
 		// run the SQL against the PDO connection. Then we can calculate the time it
 		// took to execute and log the query SQL, bindings and time in our memory.
@@ -552,17 +597,72 @@ protected function run($query, $bindings, Closure $callback)
 		// lot more helpful to the developer instead of just the database's errors.
 		catch (\Exception $e)
 		{
-			throw new QueryException($query, $this->prepareBindings($bindings), $e);
+			throw new QueryException(
+				$query, $this->prepareBindings($bindings), $e
+			);
 		}
 
-		// Once we have run the query we will calculate the time that it took to run and
-		// then log the query, bindings, and execution time so we will report them on
-		// the event that the developer needs them. We'll log time in milliseconds.
-		$time = $this->getElapsedTime($start);
+		return $result;
+	}
 
-		$this->logQuery($query, $bindings, $time);
+	/**
+	 * Handle a query exception that occurred during query execution.
+	 *
+	 * @param  \Illuminate\Database\QueryException  $e
+	 * @param  string    $query
+	 * @param  array     $bindings
+	 * @param  \Closure  $callback
+	 * @return mixed
+	 */
+	protected function tryAgainIfCausedByLostConnection(QueryException $e, $query, $bindings, $callback)
+	{
+		if ($this->causedByLostConnection($e))
+		{
+			$this->reconnect();
 
-		return $result;
+			return $this->runQueryCallback($query, $bindings, $callback);
+		}
+
+		throw $e;
+	}
+
+	/**
+	 * Determine if the given exception was caused by a lost connection.
+	 *
+	 * @param  \Illuminate\Database\QueryException
+	 * @return bool
+	 */
+	protected function causedByLostConnection(QueryException $e)
+	{
+		return str_contains($e->getPrevious()->getMessage(), 'server has gone away');
+	}
+
+	/**
+	 * Reconnect to the database.
+	 *
+	 * @return void
+	 */
+	public function reconnect()
+	{
+		if (is_callable($this->reconnector))
+		{
+			return call_user_func($this->reconnector, $this);
+		}
+
+		throw new \LogicException("Lost connection and no reconnector available.");
+	}
+
+	/**
+	 * Reconnect to the database if a PDO connection is missing.
+	 *
+	 * @return void
+	 */
+	protected function reconnectIfMissingConnection()
+	{
+		if (is_null($this->getPdo()) || is_null($this->getReadPdo()))
+		{
+			$this->reconnect();
+		}
 	}
 
 	/**
@@ -687,10 +787,10 @@ public function getReadPdo()
 	/**
 	 * Set the PDO connection.
 	 *
-	 * @param  \PDO  $pdo
+	 * @param  \PDO|null  $pdo
 	 * @return $this
 	 */
-	public function setPdo(PDO $pdo)
+	public function setPdo($pdo)
 	{
 		$this->pdo = $pdo;
 
@@ -700,16 +800,29 @@ public function setPdo(PDO $pdo)
 	/**
 	 * Set the PDO connection used for reading.
 	 *
-	 * @param  \PDO  $pdo
+	 * @param  \PDO|null  $pdo
 	 * @return $this
 	 */
-	public function setReadPdo(PDO $pdo)
+	public function setReadPdo($pdo)
 	{
 		$this->readPdo = $pdo;
 
 		return $this;
 	}
 
+	/**
+	 * Set the reconnect instance on the connection.
+	 *
+	 * @param  callable  $reconnector
+	 * @return $this
+	 */
+	public function setReconnector(callable $reconnector)
+	{
+		$this->reconnector = $reconnector;
+
+		return $this;
+	}
+
 	/**
 	 * Get the database connection name.
 	 *

src/Illuminate/Database/DatabaseManager.php

@@ -76,11 +76,13 @@ public function connection($name = null)
 	 */
 	public function reconnect($name = null)
 	{
-		$name = $name ?: $this->getDefaultConnection();
+		$this->disconnect($name = $name ?: $this->getDefaultConnection());
 
-		$this->disconnect($name);
+		$fresh = $this->makeConnection($name);
 
-		return $this->connection($name);
+		return $this->connections[$name]
+                                ->setPdo($fresh->getPdo())
+                                ->setReadPdo($fresh->getReadPdo());
 	}
 
 	/**
@@ -93,7 +95,10 @@ public function disconnect($name = null)
 	{
 		$name = $name ?: $this->getDefaultConnection();
 
-		unset($this->connections[$name]);
+		if (isset($this->connections[$name]))
+		{
+			$this->connections[$name]->setPdo(null)->setReadPdo(null);
+		}
 	}
 
 	/**
@@ -160,6 +165,14 @@ protected function prepare(Connection $connection)
 			return $app['paginator'];
 		});
 
+		// Here we'll set a reconnector callback. This reconnector can be any callable
+		// so we will set a Closure to reconnect from this manager with the name of
+		// the connection, which will allow us to reconnect from the connections.
+		$connection->setReconnector(function($connection)
+		{
+			$this->reconnect($connection->getName());
+		});
+
 		return $connection;
 	}
 

src/Illuminate/Database/QueryException.php

@@ -28,6 +28,8 @@ class QueryException extends PDOException {
 	 */
 	public function __construct($sql, array $bindings, $previous)
 	{
+		parent::__construct('', 0, $previous);
+
 		$this->sql = $sql;
 		$this->bindings = $bindings;
 		$this->previous = $previous;

src/Illuminate/Foundation/changes.json

@@ -30,7 +30,8 @@
 		{"message": "Added 'contains' method to base Collection.", "backport": null},
 		{"message": "Allow 'where' route constraints to be passed in array definition of Route.", "backport": null},
 		{"message": "Properly support Route 'where' constraints on a Route group.", "backport": null},
-		{"message": "When 'increment' or 'decrement' is called on a single Model instance, the local attribute value is updated as well.", "backport": null}
+		{"message": "When 'increment' or 'decrement' is called on a single Model instance, the local attribute value is updated as well.", "backport": null},
+		{"message": "Automatically retry queries on database connections that have 'gone away'.", "backport": null}
 	],
 	"4.1.*": [
 		{"message": "Added new SSH task runner tools.", "backport": null},