slides for a talk I gave in Dublin Google buildings in March 2011

1. Multi-tenanted CMSes (with some PHP)

3. Install once, maintain/upgrade that one instance

4. Many domain names

5. Many configurations

7. Skin/Theme details

8. User-uploaded file locations

10. install one copy of software

11. all instance data, configs, etc., installed automatically or using a “point and click” installer

12. Easier to maintain and upgrade

13. fix in one place, fix everywhere. upgrade once, upgrade everywhere

14. conversely: bugs/errors are universal, so be careful

15. Less resources needed

16. less HD space, as only one software instance

17. bytecode caching (APC, etc) for just 1 CMS copy, thus less file-access

19. all have tutorials explaining how to do it (not built into core)

20. Wordpress

21. WordPress-MU so cool it was written into the core

22. Salesforce

23. Google Apps

24. Why is it not more prevalent in OSS?

26. Finds config associated with domain name

27. Sets site-specific variables such as db details, file locations, theme details

29. WordPress MU uses one database

30. One table holds details of each domain

31. WP searches table to find ID of blog associated with domain name

32. Each blog's details kept in numbered tables in the same database (eg: wp_2_links, wp_23_links, etc)

33. KV-WebME uses multiple databases

34. Config found using sym-links in file-system

35. Each site's config kept in a separate directory on the filesystem

36. Proxy Config /home/webme /public_html/index.php /.private/config.php /sites.aliases/kvsites.ie /sites/kv-2-30/config.php

37. Proxy Config <?php $host=preg_replace( '/^www/', '', preg_replace( '/[^a-z0-9]/', '', strtolower( $_SERVER['HTTP_HOST'] ) ) ); $cfile='/home/webme/ sites.aliases /'.$host.'/config.php'; if (!file_exists($cfile)) { $cfile='/home/webme/ sites /'.$host.'/config.php'; if (!file_exists($cfile)) { echo 'error resolving domain name &quot;' .$_SERVER['HTTP_HOST'].'&quot; to a WebME server'; exit; } } require $cfile; define('CONFIG_FILE', $cfile);

39. mod_rewrite, nginx, etc

40. File's actual location determined by config file

41. URL is /file/whatever.jpg, but that's not where it really is

42. could be /home/webme/sites/kv-2-23/f/whatever.jpg

44. user-uploaded files kept in sub-directory (/home/webme/sites/kv-2-23/f)

45. Rewrite file requests to route through a script

46. RewriteRule ^f/(.*)$ /ww.incs/get-file.php?filename=$1 [L]

47. Retrieve actual file location

48. validate the filename, check that it exists

49. Push to client

50. readfile()

52. example: /f/whatever.php.jpg <-- image or script?

53. Authentication

54. require logged-in user, or that the user be a member of a certain group

55. Logging

56. record details such as what user viewed the file, push the file access to a live log view, etc.

57. Modification

58. if an image is /f/image.jpg , how about resizing it if called as /f/image.jpg,width=200

60. Keep version number of core database tables in config file.

61. Example: 'version'=>'32',

62. Hard-code version number into root /index.php

63. If versions don't match, run upgrade script, then re-save the config file with latest version if (!isset($DBVARS['version']) || $DBVARS['version']<32 ) { redirect('/ww.incs/upgrade.php'); }

65. or...

66. Maintain a reference installation, and copy that one when creating new installation

68. Prepopulate with sample data

69. Customise