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Message Queues and Drupal

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Presented at Oklahoma Drupal Users Group on November 21, 2013.

Presented at Oklahoma Drupal Users Group on November 21, 2013.

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  • Commonly used message queues include Redis – RabbitMQ – IronMQ (service) – Amazon SQS/SNS
  • - a datastore for messages to be consumed – like a mailbox
    - used for parallel processing, ensuring that a task is performed without blocking the user experience
    - scalability – typically think vertical (server size) or horizontal (more servers) – queues allow you to scale time and smooth spikes... great for rate-limited APIs
    - decoupling
  • Many configurations possible... two most common
    Producer/Consumer – producers create messages, consumers claim them when they begin working on them, release them on failure, delete on completion – i.e. Parallel processing
    Publisher/Subscriber – publishers create messages, subscribers consume them as long as they are in the queue, message eventually expires and disappears from queue – i.e. Data feeds
  • - uploading videos that need to be encoded
    - GitHub uses queues extensively... most of the work their service does is in the background
    - Drupal. Several modules implement queues (i.e. Notifications, Batch API) – every time you enable a module, it gets added to a queue to check for updates
  • Queue-list will list all available queues to run
    Queue-run will run them (but will always delete items) – advantage over cron is that cron processes can only be run 1 at a time – queue-run can be invoked as much as you want
  • Note: this is only necessary if Drupal is also acting as the consumer/subscriber. This is not necessary is Drupal is just producing or publishing messages to a queue to be consumed by something else.
  • Actions: Send alert with PagerDuty... spin up new workers...
  • Transcript

    • 1. Message Queues and Drupal
    • 2. About Me ● ● ● ● Name: Brian Altenhofel IRC: VeggieMeat Twitter: @BrianAltenhofel Drupal: #550616 What I Do: Commerce, Third-party APIs, Migrations, Devops, anything with data... Favorite Tools: Vim, Scotch, Padron Serie 1926 No. 1 Maduro
    • 3. What are message queues?
    • 4. Consumer Producer Producer Queue Consumer Consumer Producer What are message queues? Publisher Publisher Publisher Subscriber Queue Subscriber Subscriber
    • 5. You already use queues.
    • 6. In Drupal...
    • 7. Queues are pluggable Backends available on Drupal.org: AWS SQS – http://drupal.org/project/aws_sqs Beanstalkd – http://drupal.org/project/beanstalkd Redis – http://drupal.org/project/redis STOMP – http://drupal.org/project/stomp (And.... still in sandbox but ready to go...) Openstack Marconi http://drupal.org/sandbox/BrianAltenhofel/2107851
    • 8. Using a Different Queue As easy as: ● Global: $conf['queue_default_class'] = 'MarconiQueue'; ● Specific queue $conf['queue_class_{queue_name}'] = 'MarconiQueue';
    • 9. Queues and Drush ● drush queue-list ● drush queue-run [queue_name]
    • 10. Code.
    • 11. Code. function my_module_create_queue() {   $queue = DrupalQueue::get('my_queue');   $queue­>createQueue(); }
    • 12. Code. function my_module_create_queue_item() {   $queue = DrupalQueue::get('my_queue');   $queue_data = array(     'my_key' => 'my_value',   );   return $queue­>createItem($queue_data); }
    • 13. Code. function my_module_count_queue_items() {   $queue = DrupalQueue::get('my_queue');      return $queue­>numberOfItems(); }
    • 14. Code. function my_module_process_queue_item() {   $queue = DrupalQueue::get('my_queue');   $item = $queue­>claimItem(30);   if ($item && $item['my_key'] == 'my_value') {     $queue­>deleteItem($item);   }   else {     $queue­>releaseItem($item);   } }
    • 15. Code. function my_module_cron_queue_info() {   $queues['my_queue'] = array(     'worker callback' =>                                 'my_module_process_queue_item',     'time' => 60,     // Time for cron to spend on this queue, not     // the lease time.   );   return $queues; }
    • 16. It's really that simple.
    • 17. Debugging ● watchdog() is a Drupaler's best friend ● Log everything (for both your sanity and insanity) ● (probably want to ship these logs if you're processing a lot of items) (if you want to get started on that): http://www.youtube.com/watch?v=p0Av29yaBEI
    • 18. Monitoring ● Monitor queue depths with your favorite tool (Nagios, Zabbix, Zenoss, etc.) ● In a pinch, you can get an idea with $queue->numberOfItems(). ● Take action if queues get too deep
    • 19. Any questions? @BrianAltenhofel IRC: VeggieMeat (MANY channels) brian.altenhofel@vmdoh.com

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