Intro to drupal_7_architecture
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This document provides an overview of Drupal architecture, including: - The typical technology stack of OS, web server, PHP, database, and Drupal software. - How requests are routed through Drupal's bootstrap process and menu system before being returned as HTML. - Common patterns in Drupal like hooks, structured data arrays, and modules altering output. - Key concepts like entities, bundles, and fields that make up content types. - Questions to consider when planning a Drupal site like available functionality and theming.
![/index.php?q=node/1
/node/1
mod_rewrite in .htaccess
$_GET['q'] will contain 'node/1'
A typical request starts with mod_rewrite.
15](https://image.slidesharecdn.com/introtodrupal7architecture-150719161606-lva1-app6891/85/Intro-to-drupal_7_architecture-15-320.jpg)
![index.php
menu system
Which function should this path be mapped to?
$items['node/%node'] = array(
'page callback' => 'node_page_view',
'page arguments' => array(1),
'access callback' => 'node_access',
'access arguments' => array('view', 1),
);
index.php invokes the menu system, which handles much more
than menus. The menu item that maps to node/1 can be found in
node.module.
16](https://image.slidesharecdn.com/introtodrupal7architecture-150719161606-lva1-app6891/85/Intro-to-drupal_7_architecture-16-320.jpg)
![index.php
menu system
Does this user have permission to access this path?
$items['node/%node'] = array(
'page callback' => 'node_page_view',
'page arguments' => array(1),
'access callback' => 'node_access',
'access arguments' => array('view', 1),
);
node.module tells the menu system to invoke a function
(node_access()) to determine whether the current user has
permission.
17](https://image.slidesharecdn.com/introtodrupal7architecture-150719161606-lva1-app6891/85/Intro-to-drupal_7_architecture-17-320.jpg)
![tail -f /var/log/php/error.log
[07-Sep-2011 16:25:02] PHP Fatal error:
Call to undefined function int() in
bgstat.module on line 41
Watch the error log to find out what’s going on:
PHP will always tell you what went wrong in its log. If you've
defined a PHP error log in php.ini, you can watch it in real time
with tail -f.
36](https://image.slidesharecdn.com/introtodrupal7architecture-150719161606-lva1-app6891/85/Intro-to-drupal_7_architecture-36-320.jpg)
![egrep -rn mail . | grep variable_set
./includes/install.core.inc:1802:
variable_set('site_mail', $form_state['values']
['site_mail']);
./includes/install.core.inc:1813:
variable_set('update_notify_emails', array($form_state
['values']['account']['mail']));
./modules/openid/openid.test:323:
variable_set('user_email_verification',TRUE);
...
There we go. The codebase is like a rich porridge, waiting for you
to sift through and find the tasty lumps.
38](https://image.slidesharecdn.com/introtodrupal7architecture-150719161606-lva1-app6891/85/Intro-to-drupal_7_architecture-38-320.jpg)
Intro to drupal_7_architecture
- 1. An Introduction to Drupal Architecture JohnVanDyk DrupalCamp Des Moines, Iowa September 17, 2011 1
- 2. Apache IIS OS Nginx PHP 5.2.5 Stack with OS, webserver and PHP. Most people use mod_php but deployments with engineers at the helm sometimes use FastCGI. PHP 5.2.4 with the 5.2.5 security backport is fine too (Ubuntu 8.0.4). 2
- 3. Apache IIS OS Nginx hash date SimpleXMLjson dom SPLpcre filter xmlsession gd pdo pdo_mysql PHP Some PHP extensions are required. 3
- 5. Apache IIS OS Nginx PHP 5.2.5 MySQL 5.0.15 MariaDB 5.1.44 Drupal 7 Drupal sits atop the stack. 5
- 6. Apache IIS OS Nginx PHP 5.2.5 MySQL 5.0.15 MariaDB 5.1.44 Drupal 7 Varnish Varnish can be added to the front end for fast RAM-based response to anonymous users. 6
- 7. Apache Load Balancer PHP 5.2.5 MySQL Drupal 7 OS OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP Drupal 7 OS Webheads can be scaled out. 7
- 8. Apache Load Balancer PHP 5.2.5 MySQL Master Drupal 7 OS OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP 5.2.5 Drupal 7 OS Apache PHP Drupal 7 OS MySQL Slaves OS MySQL Slaves OS MySQL Slaves OS MySQL Slaves OS Databases can be scaled out. Show master-slave but master- master is also a possibility. See http://www.jochus.be/site/ 2011-01-13/drupal/drupal-master-master-replication-architecture for an example. 8
- 9. Source: Nate Haug, Lullabot Scaling the Grammys. DrupalCamp Denver 2010. 214 million hits in six hours at peak. Database load: 5%. Apache load: 1%. 9
- 10. You will not hack core. You should only modify the locations shown in green. Modifying the other files will inevitably lead to grief. 10
- 11. Development Site Local settings, including database connection info, are in sites/all/ dev.local. 11
- 12. Live Site On the live site settings are in a site-specific directory. 12
- 13. http://www.doodlepress.co.uk/item/1460 Drupal 7 Architecture Drupal architecture. Each include file has a different color and their interrelationships are shown. Uh...just kidding. 13
- 14. Browser request: GET /node/1 Bootstrap (includes/bootstrap.inc) - brings session, database, variables online Menu System (router) - maps URL to a function - checks access control - may bring functions into scope - calls function to build page data structure - calls function to theme page (look and feel) - page returned to client It is important for a developer to understand the sequence of events that occur when a request is processed by Drupal. 14
- 15. /index.php?q=node/1 /node/1 mod_rewrite in .htaccess $_GET['q'] will contain 'node/1' A typical request starts with mod_rewrite. 15
- 16. index.php menu system Which function should this path be mapped to? $items['node/%node'] = array( 'page callback' => 'node_page_view', 'page arguments' => array(1), 'access callback' => 'node_access', 'access arguments' => array('view', 1), ); index.php invokes the menu system, which handles much more than menus. The menu item that maps to node/1 can be found in node.module. 16
- 17. index.php menu system Does this user have permission to access this path? $items['node/%node'] = array( 'page callback' => 'node_page_view', 'page arguments' => array(1), 'access callback' => 'node_access', 'access arguments' => array('view', 1), ); node.module tells the menu system to invoke a function (node_access()) to determine whether the current user has permission. 17
- 18. index.php menu system node.module /** * Menu callback; view a single node. */ function node_page_view($node) { ... } The page callback for the path node/1 is 'node_page_view'. That's the name of the function that is called if the user has permission to view the page. 18
- 19. index.php menu system node.module hook_node_load() book.module comment.module forum.module user.module book_node_load() comment_node_load() forum_node_load() user_node_load() Other modules have a say in the loading of the node object. Many of these hooks (better thought of as "events") happen during the building of a page. 19
- 20. index.php menu system A large array with the node's data structure is returned to the menu system. 20
- 21. index.php menu system node.module hook_node_view_alter() drupalcorn.module drupalcorn_node_view_alter() Other modules may alter the final data structure. We've seen three common patterns that pervade Drupal: (1) hooks allow other modules to respond to events; (2) Drupal uses large structured arrays, and (3) other modules may alter these arrays once built. 21
- 22. index.php menu system delivery callback drupal_render_page() theme() page.tpl.php node.tpl.php block.tpl.php The menu system passes the structure array to a delivery callback which turns the array into HTML by rendering it; that is, passing it through Drupal's template engine. Template files (.tpl.php, pronounced "tipple-fipp") in the current theme are used to create the HTML. 22
- 23. index.php The HTML is then returned to the browser. 23
- 24. Common Library Database API Fields API Entity API N o d e s U s e r s T a x o n o m y C o m m e n t s Form API Menu API Block API Locali zation Views Template Preprocessing Theme Modules add functionality here Block diagram if you need a mental model. This doesnʼt have nearly enough dimensions to describe what actually happens. If you asked 5 developers to make Drupal block diagrams, you'd get 5 different diagrams. Hopefully this one helps someone. 24
- 25. "Entities" Node: a piece of content User: a user account Taxonomy: categories for tagging/classification Comment: content with a parent 25
- 26. An Entity has Bundles Node Title Body Title Body Page An entity can be thought of as a base object, and bundles are subclasses. For example, a node is an entity while the bundle of fields that make up a page are a type of node. 26
- 27. An Entity has Bundles Title Body Page Title Body Article Tags Image These are types of nodes. Each has a bundle of fields. 27
- 28. A Bundle has Fields Title Body Article Tags Image text_long text_with_summary taxonomy_term_reference image And each field has a type. 28
- 29. Not SQL Fields Title Body Article Tags Image text_with_summary taxonomy_term_reference These are more than SQL fields. text_with_summary autogenerates a summary. taxonomy_term_reference splits multiple tags into separate records. These are Drupal fields. 29
- 30. In the Real World "Entity" = node | user | comment | taxonomy "Bundle" = "Content Type" You assemble content types from fields using the UI. Part of the conversation with your client! Nobody says "let's create a new Node Bundle and call it Bug Report". 30
- 31. Before Building a Site • What content types and fields? • How will the data get in? (Forms) • How will the data get out? (Views) • Who may create/view/delete data? (Permissions) • What additional functionality? (Modules) • How can we make it pretty? (Theming) Questions to map client needs to Drupal concepts. 31
- 32. http://api.drupal.org Your home for API-related searches. 32
- 33. http://drupal.org/project/examples Simple implementations of APIs. You can base your own work on these examples. 33
- 34. Bonus! Two tools I use all the time. 34
- 35. Defeating the White Screen of Death error_log = /var/log/php/error.log Define PHP error log in php.ini: I close with two essential tools. First, don't be frightened by the WSOD. 35
- 36. tail -f /var/log/php/error.log [07-Sep-2011 16:25:02] PHP Fatal error: Call to undefined function int() in bgstat.module on line 41 Watch the error log to find out what’s going on: PHP will always tell you what went wrong in its log. If you've defined a PHP error log in php.ini, you can watch it in real time with tail -f. 36
- 37. Where is the code? egrep -rn searchstring . Quickly search the codebase for a function: Second, don't be overwhelmed with the codebase. egrep and pipes can help you find where functions live and where things happen. Example: where are mail-related variables set? 37
- 38. egrep -rn mail . | grep variable_set ./includes/install.core.inc:1802: variable_set('site_mail', $form_state['values'] ['site_mail']); ./includes/install.core.inc:1813: variable_set('update_notify_emails', array($form_state ['values']['account']['mail'])); ./modules/openid/openid.test:323: variable_set('user_email_verification',TRUE); ... There we go. The codebase is like a rich porridge, waiting for you to sift through and find the tasty lumps. 38
- 39. Thanks! Hopefully these help create a big picture of how Drupal works.This only scratches the surface. Now get your debugger working and explore Drupal core on your own! 39