batch_example.module in Examples for Developers 6

This is an example outlining how a module can define batches.

Batches allow heavy processing to be spread out over several page requests, thus ensuring that the processing does not get interrupted because of a PHP timeout, while allowing the user to receive feedback on the progress of the ongoing operations.

File

batch_example/batch_example.module

<?php

/**
 * @file
 * This is an example outlining how a module can define batches.
 *
 * Batches allow heavy processing to be spread out over several page
 * requests, thus ensuring that the processing does not get interrupted
 * because of a PHP timeout, while allowing the user to receive feedback
 * on the progress of the ongoing operations.
 */

/**
 * @defgroup batch_example Example: Batch API
 * @ingroup examples
 * @{
 * Examples using batch API. (drupal 6)
 *
 * 2 'harmless' batches are defined :
 * batch 1 : Load 100 times the node with the lowest nid
 * batch 2 : Load all nodes, 20 times
 *           (uses a progressive op : load nodes by groups of 5)
 *
 * The module defines the following pages :
 * - /batch_example/example_1 :
 *   Simple form, lets you pick the batch that should be executed
 * - /batch_example/example_2 :
 *   Multistep form : perform batch 1 and batch 2 as separate submission steps.
 * - /batch_example/example_3 :
 *   No form - start a batch simply by clicking a link
 *   (not really user friendly, should probably be avoided)
 *
 * This example is part of the Examples for Developers Project which
 * you can download and experiment with here:
 * http://drupal.org/project/examples
 */

/**
 * Implementation of hook_menu().
 */
function batch_example_menu() {
  $items = array();
  $items['batch_example'] = array(
    'title' => 'Batch example',
    'page callback' => 'drupal_get_form',
    'page arguments' => array(
      'batch_example_simple_form',
    ),
    'access callback' => TRUE,
  );
  $items['batch_example/example_1'] = array(
    'title' => 'Simple form',
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'weight' => 0,
  );
  $items['batch_example/example_2'] = array(
    'title' => 'Multistep form',
    'page callback' => 'drupal_get_form',
    'page arguments' => array(
      'batch_example_multistep_form',
    ),
    'access callback' => TRUE,
    'type' => MENU_LOCAL_TASK,
    'weight' => 1,
  );
  $items['batch_example/example_3'] = array(
    'title' => 'No form',
    'page callback' => 'batch_example_page',
    'access callback' => TRUE,
    'type' => MENU_LOCAL_TASK,
    'weight' => 2,
  );
  return $items;
}

/**
 * Test 1 :
 * Simple form
 */
function batch_example_simple_form() {
  $form['batch'] = array(
    '#type' => 'select',
    '#title' => 'Choose batch',
    '#options' => array(
      'batch_1' => 'batch 1 - load a node 100 times',
      'batch_2' => 'batch 2 - load all nodes, 20 times',
    ),
  );
  $form['submit'] = array(
    '#type' => 'submit',
    '#value' => 'Go',
  );
  return $form;
}

/**
 * Submit handler for the form 'batch_example_simple_form'.
 *
 * This submit handler will be called when the user clicks 'Go' in
 * the form.
 */
function batch_example_simple_form_submit($form, &$form_state) {

  // Dropdown will return 'batch_1' or 'batch_2'
  $values =& $form_state['values'];

  // Create a string with the function name 'batch_example_batch_1'
  // or 'batch_example_batch_2'
  $function = 'batch_example_' . $values['batch'];

  // Load the $batch variable with an array containing the details
  // of what to run
  $batch = $function();

  // Start the batch process running
  batch_set($batch);

  // Redirection takes place as usual.
  $form_state['redirect'] = 'batch_example/example_2';
}

/**
 * Multistep form
 */
function batch_example_multistep_form($form_state = NULL) {
  $step = isset($form_state['storage']['step']) ? $form_state['storage']['step'] : 1;
  $form['step_display'] = array(
    '#type' => 'item',
    '#value' => 'step ' . $step,
  );
  if ($step < 3) {
    $form['submit'] = array(
      '#type' => 'submit',
      '#value' => 'Go',
    );
  }
  return $form;
}
function batch_example_multistep_form_submit($form, &$form_state) {
  $step = isset($form_state['storage']['step']) ? $form_state['storage']['step'] : 1;
  switch ($step) {
    case 1:
      drupal_set_message('step 1 submitted');
      batch_set(batch_example_batch_1());
      break;
    case 2:
      drupal_set_message('step 2 submitted');
      batch_set(batch_example_batch_2());

      // this does not seem to work ?
      $form_state['redirect'] = 'batch_example/example_3';
      break;
  }
  $form_state['storage']['step'] = $step + 1;
}
function batch_example_page() {
  batch_set(batch_example_batch_1());

  // We're not inside a form submission workflow, so we have to
  // manually trigger the batch processing - this issues a
  // drupal_goto and thus ends current request.
  // We also specify here where we want to redirect after batch
  // processing.
  batch_process('batch_example/example_1');
}

/**
 * Batch 1 : Load 100 times the node with the lowest nid
 *
 * This method does not yet do the work; it simply builds an array
 * of the work which needs to be done during the batch processing.
 * The results of this function will be passed to the batch processor
 * for actual processing.
 */
function batch_example_batch_1() {
  $nid = db_result(db_query_range("SELECT nid FROM {node} ORDER BY nid ASC", 0, 1));
  $operations = array();
  for ($i = 0; $i < 100; $i++) {
    $operations[] = array(
      'batch_example_op_1',
      array(
        $nid,
      ),
    );
  }

  // Create an array which contains an array of the operations to
  // perform and a method to call when the operations are all finished
  $batch = array(
    'operations' => $operations,
    'finished' => 'batch_example_finished',
  );
  return $batch;
}

/**
 * Batch operation for batch 1 : load a node...
 */
function batch_example_op_1($nid, &$context) {
  $node = node_load($nid, NULL, TRUE);

  // Store some result for post-processing in the finished callback.
  $context['results'][] = $node->nid . ' : ' . check_plain($node->title);

  // Optional message displayed under the progressbar.
  $context['message'] = t('Loading @title', array(
    '@title' => $node->title,
  ));
}

/**
 * Batch 2 : load all nodes 5 by 5, 20 times (Multipart operation)
 *
 * This method does not yet do the work; it simply builds an array
 * of the work which needs to be done during the batch processing.
 * The results of this function will be passed to the batch
 * processor for actual processing.
 */
function batch_example_batch_2() {
  $operations = array();
  for ($i = 0; $i < 20; $i++) {
    $operations[] = array(
      'batch_example_op_2',
      array(),
    );
  }
  $batch = array(
    'operations' => $operations,
    'finished' => 'batch_example_finished',
    // We can define custom messages instead of the default ones.
    'title' => t('Processing batch 2'),
    'init_message' => t('Batch 2 is starting.'),
    'progress_message' => t('Processed @current out of @total.'),
    'error_message' => t('Batch 2 has encountered an error.'),
  );
  return $batch;
}

/**
 * Batch operation for batch 2 : load all nodes, 5 by five
 * This is a multipart operation, using the
 */
function batch_example_op_2(&$context) {

  // Use the $context['sandbox'] at your convenience to store the
  // information needed to track progression between successive calls.
  if (!isset($context['sandbox']['progress'])) {
    $context['sandbox']['progress'] = 0;
    $context['sandbox']['current_node'] = 0;
    $context['sandbox']['max'] = db_result(db_query('SELECT COUNT(DISTINCT nid) FROM {node}'));
  }

  // Process nodes by groups of 5 (arbitrary value).
  // When a group of five is processed, the batch update engine determines
  // whether it should continue processing in the same request or provide
  // progress feedback to the user and wait for the next request.
  $limit = 5;

  // Retrieve the next group of nids.
  $result = db_query_range("SELECT nid FROM {node} WHERE nid > %d ORDER BY nid ASC", $context['sandbox']['current_node'], 0, $limit);
  while ($row = db_fetch_array($result)) {

    // Here we actually perform our dummy 'processing' on the current node.
    $node = node_load($row['nid'], NULL, TRUE);

    // Store some result for post-processing in the finished callback.
    $context['results'][] = $node->nid . ' : ' . check_plain($node->title);

    // Update our progress information.
    $context['sandbox']['progress']++;
    $context['sandbox']['current_node'] = $node->nid;
    $context['message'] = check_plain($node->title);
  }

  // Inform the batch engine that we are not finished,
  // and provide an estimation of the completion level we reached.
  if ($context['sandbox']['progress'] >= $context['sandbox']['max']) {

    // We should always check if the current progress is equal or greater to
    // the total number of items to process. For example, if a node is added
    // while this batch process is running, the progress value will end up being
    // one greater than the max value. This will cause an infinite loop. We
    // prevent this from happening by always checking if progress is greater
    // than or equal to max.
    $context['finished'] = 1;
  }
  else {
    $context['finished'] = $context['sandbox']['progress'] / $context['sandbox']['max'];
  }
}

/**
 * Batch 'finished' callback used by both batch 1 and batch 2
 */
function batch_example_finished($success, $results, $operations) {
  if ($success) {

    // Here we could do something meaningful with the results.
    // We just display the number of nodes we processed...
    $message = count($results) . ' processed.';
  }
  else {

    // An error occurred.
    // $operations contains the operations that remained unprocessed.
    $error_operation = reset($operations);
    $message = 'An error occurred while processing ' . $error_operation[0] . ' with arguments :' . print_r($error_operation[0], TRUE);
  }
  drupal_set_message($message);
}

/**
 * @} End of "defgroup batch_example".
 */

Functions

Name	Description
batch_example_batch_1	Batch 1 : Load 100 times the node with the lowest nid
batch_example_batch_2	Batch 2 : load all nodes 5 by 5, 20 times (Multipart operation)
batch_example_finished	Batch 'finished' callback used by both batch 1 and batch 2
batch_example_menu	Implementation of hook_menu().
batch_example_multistep_form	Multistep form
batch_example_multistep_form_submit
batch_example_op_1	Batch operation for batch 1 : load a node...
batch_example_op_2	Batch operation for batch 2 : load all nodes, 5 by five This is a multipart operation, using the
batch_example_page
batch_example_simple_form	Test 1 : Simple form
batch_example_simple_form_submit	Submit handler for the form 'batch_example_simple_form'.