class Log in Drupal 9

Database query logger.

We log queries in a separate object rather than in the connection object because we want to be able to see all queries sent to a given database, not database target. If we logged the queries in each connection object we would not be able to track what queries went to which target.

Every connection has one and only one logging object on it for all targets and logging keys.

Hierarchy

• class \Drupal\Core\Database\Log

4 files declare their use of Log

Error.php in core/lib/Drupal/Core/Utility/Error.php

LoggingTest.php in core/tests/Drupal/KernelTests/Core/Database/LoggingTest.php

LogTest.php in core/tests/Drupal/Tests/Core/Database/LogTest.php

StubConnection.php in core/tests/Drupal/Tests/Core/Database/Stub/StubConnection.php

File

core/lib/Drupal/Core/Database/Log.php, line 16

Namespace

Drupal\Core\Database

class Log {

  /**
   * Cache of logged queries. This will only be used if the query logger is enabled.
   *
   * The structure for the logging array is as follows:
   *
   * array(
   *   $logging_key = array(
   *     array('query' => '', 'args' => array(), 'caller' => '', 'target' => '', 'time' => 0, 'start' => 0),
   *     array('query' => '', 'args' => array(), 'caller' => '', 'target' => '', 'time' => 0, 'start' => 0),
   *   ),
   * );
   *
   * @var array
   */
  protected $queryLog = [];

  /**
   * The connection key for which this object is logging.
   *
   * @var string
   */
  protected $connectionKey = 'default';

  /**
   * Constructor.
   *
   * @param $key
   *   The database connection key for which to enable logging.
   */
  public function __construct($key = 'default') {
    $this->connectionKey = $key;
  }

  /**
   * Begin logging queries to the specified connection and logging key.
   *
   * If the specified logging key is already running this method does nothing.
   *
   * @param $logging_key
   *   The identification key for this log request. By specifying different
   *   logging keys we are able to start and stop multiple logging runs
   *   simultaneously without them colliding.
   */
  public function start($logging_key) {
    if (empty($this->queryLog[$logging_key])) {
      $this
        ->clear($logging_key);
    }
  }

  /**
   * Retrieve the query log for the specified logging key so far.
   *
   * @param $logging_key
   *   The logging key to fetch.
   *
   * @return
   *   An indexed array of all query records for this logging key.
   */
  public function get($logging_key) {
    return $this->queryLog[$logging_key];
  }

  /**
   * Empty the query log for the specified logging key.
   *
   * This method does not stop logging, it simply clears the log. To stop
   * logging, use the end() method.
   *
   * @param $logging_key
   *   The logging key to empty.
   */
  public function clear($logging_key) {
    $this->queryLog[$logging_key] = [];
  }

  /**
   * Stop logging for the specified logging key.
   *
   * @param $logging_key
   *   The logging key to stop.
   */
  public function end($logging_key) {
    unset($this->queryLog[$logging_key]);
  }

  /**
   * Log a query to all active logging keys.
   *
   * @param \Drupal\Core\Database\StatementInterface $statement
   *   The prepared statement object to log.
   * @param array $args
   *   The arguments passed to the statement object.
   * @param float $time
   *   The time the query took to execute as a float (in seconds with
   *   microsecond precision).
   * @param float $start
   *   The time the query started as a float (in seconds since the Unix epoch
   *   with microsecond precision).
   */
  public function log(StatementInterface $statement, $args, $time, float $start = NULL) {
    foreach (array_keys($this->queryLog) as $key) {

      // @todo Remove the method_exists check for getConnectionTarget in
      //   Drupal 10.
      // @see https://www.drupal.org/project/drupal/issues/3210310
      $this->queryLog[$key][] = [
        'query' => $statement
          ->getQueryString(),
        'args' => $args,
        'target' => method_exists($statement, 'getConnectionTarget') ? $statement
          ->getConnectionTarget() : $statement->dbh
          ->getTarget(),
        'caller' => $this
          ->findCaller(),
        'time' => $time,
        'start' => $start,
      ];
    }
  }

  /**
   * Determine the routine that called this query.
   *
   * Traversing the call stack from the very first call made during the
   * request, we define "the routine that called this query" as the last entry
   * in the call stack that is not any method called from the namespace of the
   * database driver, is not inside the Drupal\Core\Database namespace and does
   * have a file (which excludes call_user_func_array(), anonymous functions
   * and similar). That makes the climbing logic very simple, and handles the
   * variable stack depth caused by the query builders.
   *
   * See the @link http://php.net/debug_backtrace debug_backtrace() @endlink
   * function.
   *
   * @return
   *   This method returns a stack trace entry similar to that generated by
   *   debug_backtrace(). However, it flattens the trace entry and the trace
   *   entry before it so that we get the function and args of the function that
   *   called into the database system, not the function and args of the
   *   database call itself.
   */
  public function findCaller() {
    $driver_namespace = Database::getConnectionInfo($this->connectionKey)['default']['namespace'];
    $stack = static::removeDatabaseEntries($this
      ->getDebugBacktrace(), $driver_namespace);

    // Return the first function call whose stack entry has a 'file' key, that
    // is, it is not a callback or a closure.
    for ($i = 0; $i < count($stack); $i++) {
      if (!empty($stack[$i]['file'])) {
        return [
          'file' => $stack[$i]['file'],
          'line' => $stack[$i]['line'],
          'function' => $stack[$i + 1]['function'],
          'class' => $stack[$i + 1]['class'] ?? NULL,
          'type' => $stack[$i + 1]['type'] ?? NULL,
          'args' => $stack[$i + 1]['args'] ?? [],
        ];
      }
    }
  }

  /**
   * Removes database related calls from a backtrace array.
   *
   * @param array $backtrace
   *   A standard PHP backtrace. Passed by reference.
   * @param string $driver_namespace
   *   The PHP namespace of the database driver.
   *
   * @return array
   *   The cleaned backtrace array.
   */
  public static function removeDatabaseEntries(array $backtrace, string $driver_namespace) : array {

    // Starting from the very first entry processed during the request, find
    // the first function call that can be identified as a call to a
    // method/function in the database layer.
    for ($n = count($backtrace) - 1; $n >= 0; $n--) {

      // If the call was made from a function, 'class' will be empty. We give
      // it a default empty string value in that case.
      $class = $backtrace[$n]['class'] ?? '';
      if (strpos($class, __NAMESPACE__, 0) === 0 || strpos($class, $driver_namespace, 0) === 0) {
        break;
      }
    }
    return array_values(array_slice($backtrace, $n));
  }

  /**
   * Gets the debug backtrace.
   *
   * Wraps the debug_backtrace function to allow mocking results in PHPUnit
   * tests.
   *
   * @return array[]
   *   The debug backtrace.
   */
  protected function getDebugBacktrace() {
    return debug_backtrace();
  }

}

Members

Name	Modifiers	Type	Description	Overrides
Log::$connectionKey	protected	property	The connection key for which this object is logging.
Log::$queryLog	protected	property	Cache of logged queries. This will only be used if the query logger is enabled.
Log::clear	public	function	Empty the query log for the specified logging key.
Log::end	public	function	Stop logging for the specified logging key.
Log::findCaller	public	function	Determine the routine that called this query.
Log::get	public	function	Retrieve the query log for the specified logging key so far.
Log::getDebugBacktrace	protected	function	Gets the debug backtrace.
Log::log	public	function	Log a query to all active logging keys.
Log::removeDatabaseEntries	public static	function	Removes database related calls from a backtrace array.
Log::start	public	function	Begin logging queries to the specified connection and logging key.
Log::__construct	public	function	Constructor.