drupal - Drupal 6 Batch API 如何工作？

Question

我一直在成功地使用 Batch API 来执行通常会导致 PHP 超时或内存不足错误的处理，并且它一直运行良好。

我已经稍微浏览了代码，但我仍然不清楚幕后发生了什么。

熟悉这个过程的人可以描述它是如何工作的吗？

Answer 1

I've looked through the code a little, but I'm still unclear about what's happening behind the scenes.

Could someone familiar with the process describe how it works?

发生的情况是，为了避免 PHP 超时，浏览器会定期通过 AJAX ping 导致执行批处理操作的 URL ( http://example.com/batch?id= $id)。
见 _batch_page() ，这是 system_batch_page()调用的函数，“批处理”路径的菜单回调。

function _batch_page() {
  $batch = &batch_get();

  // Retrieve the current state of batch from db.
  if (isset($_REQUEST['id']) && $data = db_result(db_query("SELECT batch FROM {batch} WHERE bid = %d AND token = '%s'", $_REQUEST['id'], drupal_get_token($_REQUEST['id'])))) {
    $batch = unserialize($data);
  }
  else {
    return FALSE;
  }

  // Register database update for end of processing.
  register_shutdown_function('_batch_shutdown');

  $op = isset($_REQUEST['op']) ? $_REQUEST['op'] : '';
  $output = NULL;
  switch ($op) {
    case 'start':
      $output = _batch_start();
      break;

    case 'do':
      // JS-version AJAX callback.
      _batch_do();
      break;

    case 'do_nojs':
      // Non-JS progress page.
      $output = _batch_progress_page_nojs();
      break;

    case 'finished':
      $output = _batch_finished();
      break;
  }

  return $output;
}

在 _batch_progress_page_nojs() ，你会注意到下面的代码。

  $url = url($batch['url'], array('query' => array('id' => $batch['id'], 'op' => $new_op)));
  drupal_set_html_head('<meta http-equiv="Refresh" content="0; URL=' . $url . '">');
  $output = theme('progress_bar', $percentage, $message);
  return $output;

设置“刷新”元标记将导致页面刷新。

Drupal 7 中有类似的代码；不同的是代码已经移植了，它使用了Drupal 7实现的新功能。

  // Merge required query parameters for batch processing into those provided by
  // batch_set() or hook_batch_alter().
  $batch['url_options']['query']['id'] = $batch['id'];
  $batch['url_options']['query']['op'] = $new_op;

  $url = url($batch['url'], $batch['url_options']);
  $element = array(
    '#tag' => 'meta', 
    '#attributes' => array(
      'http-equiv' => 'Refresh', 
      'content' => '0; URL=' . $url,
    ),
  );
  drupal_add_html_head($element, 'batch_progress_meta_refresh');

  return theme('progress_bar', array('percent' => $percentage, 'message' => $message));

启用 JavaScript 后，完成所有工作的代码位于 batch.js 中。文件。

/**
 * Attaches the batch behavior to progress bars.
 */
Drupal.behaviors.batch = function (context) {
  // This behavior attaches by ID, so is only valid once on a page.
  if ($('#progress.batch-processed').size()) {
    return;
  }
  $('#progress', context).addClass('batch-processed').each(function () {
    var holder = this;
    var uri = Drupal.settings.batch.uri;
    var initMessage = Drupal.settings.batch.initMessage;
    var errorMessage = Drupal.settings.batch.errorMessage;

    // Success: redirect to the summary.
    var updateCallback = function (progress, status, pb) {
      if (progress == 100) {
        pb.stopMonitoring();
        window.location = uri+'&op=finished';
      }
    };

    var errorCallback = function (pb) {
      var div = document.createElement('p');
      div.className = 'error';
      $(div).html(errorMessage);
      $(holder).prepend(div);
      $('#wait').hide();
    };

    var progress = new Drupal.progressBar('updateprogress', updateCallback, "POST", errorCallback);
    progress.setProgress(-1, initMessage);
    $(holder).append(progress.element);
    progress.startMonitoring(uri+'&op=do', 10);
  });
};

批量 URL 的轮询以 progress.startMonitoring(uri+'&op=do', 10) 开头. batch.js 文件依赖于 Drupal.progressBar 中公开的功能，在 progress.js 中定义文件。

Drupal 7 中使用了类似的代码，它使用了一个略有不同版本的 batch.js , 和 progress.js文件。

(function ($) {

/**
 * Attaches the batch behavior to progress bars.
 */
Drupal.behaviors.batch = {
  attach: function (context, settings) {
    $('#progress', context).once('batch', function () {
      var holder = $(this);

      // Success: redirect to the summary.
      var updateCallback = function (progress, status, pb) {
        if (progress == 100) {
          pb.stopMonitoring();
          window.location = settings.batch.uri + '&op=finished';
        }
      };

      var errorCallback = function (pb) {
        holder.prepend($('<p class="error"></p>').html(settings.batch.errorMessage));
        $('#wait').hide();
      };

      var progress = new Drupal.progressBar('updateprogress', updateCallback, 'POST', errorCallback);
      progress.setProgress(-1, settings.batch.initMessage);
      holder.append(progress.element);
      progress.startMonitoring(settings.batch.uri + '&op=do', 10);
    });
  }
};

})(jQuery);

不同之处在于，从 Drupal 7 开始，所有 jQuery 代码都包含在 (function ($) { })(jQuery); 中。 ，还有 jQuery Once plugin is included with Drupal 7 . Drupal 7 还设置了 WAI-ARIA 属性以与屏幕阅读器兼容；这也发生在从 JavaScript 代码添加的 HTML 中，如下所示，在 progress.js 文件中找到。

  // The WAI-ARIA setting aria-live="polite" will announce changes after users
  // have completed their current activity and not interrupt the screen reader.
  this.element = $('<div class="progress" aria-live="polite"></div>').attr('id', id);
  this.element.html('<div class="bar"><div class="filled"></div></div>' +
                    '<div class="percentage"></div>' +
                    '<div class="message">&nbsp;</div>');

在提供批处理页面时，Drupal 设置 _batch_shutdown()作为关闭回调；当 PHP 由于超时而关闭时，该函数会更新数据库中的批处理数组。

// Drupal 6.
function _batch_shutdown() {
  if ($batch = batch_get()) {
    db_query("UPDATE {batch} SET batch = '%s' WHERE bid = %d", serialize($batch), $batch['id']);
  }
}

// Drupal 7.
function _batch_shutdown() {
  if ($batch = batch_get()) {
    db_update('batch')
      ->fields(array('batch' => serialize($batch)))
      ->condition('bid', $batch['id'])
      ->execute();
  }
}