Presentation on Publish and Subscribe from Drupalcamp Timisoara 2010.

1. Publish /
Subscribe
Alexandru Badiu

2. Me
Alexandru Badiu
Drupal user and contributor since 2003
Adulmec LLC
Drupal Romania
Drupal.ro

3. We’re goning to talk about
What is Pub/Sub
Pub/Sub in Drupal
Basic usage
Advanced features
Integration with 3rd party modules
Case study: Urbo.ro

4. What is Pub/Sub?
Messaging paradigm
Sibling of Message queues
Publisher, Subscriber, Broker
Decoupled
Topic based
Content based
Push
Pull

5. What is Pub/Sub?
Advantages
Loosely coupled
Scalable
Disadvantages
Not so scalable on large deployments
Loosely coupled

6. What is Pub/Sub?

7. Pub/Sub in Drupal
Not pure Pub / Sub
Content synchronization (tightly coupled)
Content propagation (loosely coupled)
Domain module alternative
A hybrid system (topic and content based)
The content are nodes
Supports Pull and Push
Uses XML-RPC

8. Pub/Sub in Drupal
Topics are defined by views
Content filtering is done via filters
node_save() and alternatives
Supports private channels
Token based security
Works with most CCK field types (no userreference)
Syncs taxonomy terms
Syncs files uploaded to nodes
Deletion propagation

9. Basic usage - Demo
Set up taxonomies
Set up a publisher and a channel
Set up a subscriber to that channel
Add some nodes into the queue
Push
Pull

10. Advanced usage - Demo
Using the filters
Node reference
Deletion propagation
Syncing uploaded files
Excluding nodes
Tying nodes together

11. Integration
hook_publish_prepare(&$node)
publish_node_was_changed($nid)
hook_subscribe_presave(&$node)
hook_subscribe_postsave(&$node)

12. Integration
hook_publish_prepare(&$node)
function flag_pub_sub_publish_prepare(&$node) {
$flag = flag_get_flag(FLAG_PUB_SUB_FLAG_NAME);
if ($flag == null) {
return;
}
if (!$flag->is_flagged($node->nid)) {
return;
}
$node->flag_pub_sub = array(
FLAG_PUB_SUB_FLAG_NAME => true,
);
}

13. Integration
hook_subscribe_postsave(&$node)
function flag_pub_sub_subscribe_postsave(&$node) {
$flag = flag_get_flag(FLAG_PUB_SUB_FLAG_NAME);
if ($flag == null) {
return;
}
if ($node->flag_pub_sub[FLAG_PUB_SUB_FLAG_NAME]) {
$flag->flag('flag', $node->nid);
}
}

14. Integration
publish_node_was_changed($nid)
_bulk_media_update_statistics($nid);
if (module_exists('publish')) {
publish_node_was_changed($nid);
}

15. Case study:
Urbo.ro
‣We use Pub / Sub to sync nodes
‣Custom modules for extra data
‣21 channels and subscriptions
‣57 k nodes managed

16. Thanks
andu@ctrlz.ro
http://ctrlz.ro / http://corporate.adulmec.ro
Photo credit: Flickr users Gl3am, nidhug and scattered sunshine.