Asynchronous MySQL driver

INTRODUCTION

The Asynchonous MySQL driver for Drupal, provides the option to perform asynchronous queries via DBTNG.

Still a work in progress, but seems to work ok.

REQUIREMENTS

• Drupal 7
• MySQL

INSTALLATION

• Copy (or symlink) the database subdir to the database driver location, so that Drupal can locate and use it.
• %> cd /path/to/drupal/path/to/module
• %> cp -r database /path/to/drupal/includes/database/mysql_async
• Clear cache.

CONFIGURATION

• Before enabling, remember to clear the cache.
• To enable change the driver in settings.php

<?php
  $databases['default']['default']['driver'] = 'mysql_async';
  $databases['default']['default']['async_max_connections'] = 30;
  $databases['default']['default']['async_min_connections'] = 5;

  // Use async queries for all request. Highly experimental.
  $databases['default']['default']['default_options'] = array('async' => TRUE);
?>

USAGE

Perform two heavy queries asynchronously:

<?php
  // Initiate queries.
  $q1 = db_query("MY HEAVY QUERY ONE", array(), array('async' => TRUE));
  $q2 = db_query("MY HEAVY QUERY TWO", array(), array('async' => TRUE));

  // Wait no more than 30 seconds for queries to complete.
  $until = microtime(TRUE) + 30;
  do {
    $done = $q1->rowCount(TRUE) !== NULL && $q2->rowCount(TRUE) !== NULL;
  } while (!$done && microtime(TRUE) < $until);

  // Get results.
  $r1 = $q1->rowCount(TRUE) !== NULL ? $q1->fetchAll() : NULL;
  $r2 = $q2->rowCount(TRUE) !== NULL ? $q2->fetchAll() : NULL;
  var_dump($r1);
  var_dump($r2);
?>

PREFETCH CACHE

The Drupal Mysql Async driver also contains a cache backend suitable for Cache Heuristic.

To configure:

<?php
// Add async support to the default database driver.
$databases['default']['default']['driver'] = 'mysql_async';

// Add cache backends. Note that Cache Consistent is necessary due to cache
// operations are not performed in the default database connection connection,
// and is thus potentially outside a transaction.
$conf['cache_backends'][] = 'sites/all/modules/contrib/cache_heuristic/cache_heuristic.inc';
$conf['cache_backends'][] = 'sites/all/modules/contrib/cache_consistent/cache_consistent.inc';
$conf['cache_backends'][] = 'sites/all/modules/contrib/mysql_async/mysql_async.cache.inc';

// Setup backends.
$conf['cache_default_class'] = 'HeuristicCache';
$conf['heuristic_cache_default_class'] = 'ConsistentCache';
$conf['consistent_cache_default_class'] = 'DrupalDatabaseCacheAsync';
?>

FAQ

• Q: Does my module need to require this module as a dependency?
• A: No. Your code can be backwards compatible. By using rowCount(TRUE) to check if a request has finished, your code will still work when not using the mysql_async driver.

CREDITS

Inspired by APDQC - https://www.drupal.org/project/apdqc