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Drupal has the ability to connect to multiple databases, allowing you to use Drupal’s built in database abstraction layer on more than just Drupal's primary database. Preferably you would add your configuration in the settings.php file for your site, so that all modules can interact with the new database. Drupal 7 In your settings.php: $databases = array(); $databases['default']['default'] = array( // Drupal's default credentials here. // This is where the Drupal core will store it's data. ); $databases['alternate_db']['default'] = array( // Your secondary database's credentials here. // You will be able to explicitly connect to this database from your modules. ); The way to use it in module: // Use the database we set up earlier db_set_active('alternate_db'); // Run some queries, process some data db_query('...............'); //Switch back to the default connection when finished. // other...

In my experience, there seems to be a lot of misunderstanding how Drupal caching works. I'm not talking about advanced caching mechanisms like Varnish, APC or memcache here, I'm talking about the core Drupal caching: page cache and block cache which are available in Drupal 7 core. Drupal 6 is similar but works a but differently because page caching was simplified for Drupal 7 (e.g. aggresive mode is now a available as a settings.php var) and the entire system also has become pluggable. Everybody knows this screen and the settings. But what do they exactly mean? What difference do they actually make? What do they do? Here is an attempt to explain the settings at '/admin/config/development/performance' . Page Caching: If enables, page caching will only be used for anonymous users. If you enable page caching, the entire HTML of each page will be stored in the database. This significantly reduces the amount of queries needed. This automatically means that bl...

This is the 3rd article in the series covering DRUPAL v6 bootstrap process. As the bootstrap name implies, this phase covers initializing a connection to a database. The phase begins by including 'database.inc' , which is a database abstraction layer allowing developers to use different database servers with the same code base. One of the functions defined by this library is the db_set_active() function, which is invoked by the bootstrap database phase. This function is used to activate a database used by queries in later phases or during page building and rendering. The function begins by checking if the global variable $db_url is empty. Recall that in the phase #1 - DRUPAL_BOOTSTRAP_CONFIGURATION, this variable is set to the value specified in settings.php unless it is still set to the default string of ' mysql://username:password@localhost/databasename' . In that case, $db_url is simply set to empty string ''. This would indicate a first time insta...

The previous article in this series focused on phase 1 of the Drupal bootstrap process (DRUPAL_BOOTSTRAP_CONFIGURATION). This article will now focus on the second phase - DRUPAL_BOOTSTRAP_EARLY_PAGE_CACHE. The early page cache phase is one that might not accomplish much for some Drupal sites, but for some others can play an important role in improving a site's overall performance by minimizing latency when delivering content to a user's browser. This is accomplished by caching already rendered pages for anonymous users (i.e. haven't logged in). This phase is run early in the bootstrap process as it doesn't rely on any later bootstrap phases (used to gather content and render pages) and its purpose is to keep latency to a minimum - in other words the sooner it executes, the faster a user receives the requested content. There are two forms of caching with Drupal: non-database and database. The early page cache relies on non-database mechanisms, such as file syst...

When investigating a recent rash of spam user registration on my site I began looking through Drupal core to gain a better understanding of its inner workings and how modules could be used to guard against these nuisances. Like every journey there is a beginning, and for me it all started with index.php. This is not a very big file, but it plays a vital role because access to content on any Drupal site (via HTTP GET or POST commands) is all directed to this one file. It starts off simply enough by including a bootstrap PHP file (bootstrap.inc). This file in turn defines several constants referenced throughout the Drupal code base as well as several core utility functions. Then magic begins The drupal-bootstrap function is called with the constant DRUPAL_BOOTSTRAP_FULL as argument (the function and constant previously defined by the afore-mentioend include file). This function serves to execute a series of phases in order to process all requests coming to the server. How many p...