You may know that queues can help with long-running tasks, but did you know they can help you make your application easier to debug, more performant, and scale in the cloud? Taking the real-world example of a contest app, we’ll see how easy queues can be to implement. You’ll see how the smart use of queues can enable your application to handle many more users with the same code, break components across servers, and help you keep your app responsive.

1. Architecting with Queues for
Scale and Separation
Sandy Smith
Northeast PHP 2015

2. Insert Text Here
Architecting with Queues - Sandy Smith - Northeast PHP 2015
Setting Expectations
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3. Architecting with Queues - Sandy Smith - Northeast PHP 2015
What this talk is NOT
•A queues HOWTO (though there is some)
•Benchmark bonanza
•An Azure talk (though there is some)
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4. Architecting with Queues - Sandy Smith - Northeast PHP 2015
What this talk IS
•An architecture talk
•A challenge to think differently about your applications
•A story about rapidly developing an app
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5. Architecting with Queues - Sandy Smith - Northeast PHP 2015
The Challenge
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6. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Social Contest
•Show off Azure + PHP
•People submit tweets to enter contest
•Pull specified keywords from Twitter queue (prefiltered by
Node.js app)
•Human admins filter out inappropriate content
•Humans or computer pulls out winner from approved entries,
on timer or arbitrarily
•Display latest entries and latest winners to public
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7. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Stretch goals
•Allow any size contest
•Assume global contest with distributed moderators
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8. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Quick refresher
Performance vs. Scaling
Vertical vs. Horizontal Scaling
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9. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Initial design
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10. Architecting with Queues - Sandy Smith - Northeast PHP 2015
System-level view
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Twitter
Firehose
Entries
node.js app
Contest App DB
Public
Admins

11. Architecting with Queues - Sandy Smith - Northeast PHP 2015
The real bottleneck
What’s the slowest and
most variable part of any
application?
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Architecting with Queues - Sandy Smith - Northeast PHP 2015
The real bottleneck
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13. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Traditional database design
•Group by kind
•Keep metadata with object or in metadata tables
•Objects (Document, Person, Account) are most important
•Reinforced by TableGateway, ActiveRecord patterns, and ORM
and framework module generator defaults
•Works for 80+% of cases
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14. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Tradeoffs of traditional design
•Everything’s in one table, even when you routinely only need a
subset
•Typically one master writes, replicants read
•Design is focused around what something is, not its state or
other attribute
•Requires creative solutions for horizontal scaling
•Encourages (but does not require) centralizing logic for a given
type of data
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15. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Worst of all…
•This design really didn’t show off all the stuff in Azure
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16. (We had a week left)
Architecting with Queues - Sandy Smith - Northeast PHP 2015
Redesign time
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17. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Redesign goals
•Include as much Azure stuff as is reasonable
•Implement the stretch goals of scalability
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18. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Queues to the rescue!
(Plus some other cool stuff)
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19. Architecting with Queues - Sandy Smith - Northeast PHP 2015
New approach
•Keep long term but fast storage
•Central concern is not the Thing (Entry) but Status
– Unapproved
– Approved
– Denied
– Winner
•Separate updates to long term storage from status changes
•Minimal impact to working code
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20. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Azure queuing options
Azure Queues (duh)
•Simple
•“Short”-lived (<7 days)
•Used within Azure
•Uses REST
•Can track message
processing
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Azure Service Bus
•Enterprisey
•Long-lived
•In Azure or private cloud
•Can use AMQP, REST, or
API
•Can publish/subscribe
•Can batch requests
•Can guarantee FIFO
•etc.
See https://msdn.microsoft.com/en-us/library/azure/hh767287.aspx

21. Architecting with Queues - Sandy Smith - Northeast PHP 2015
More options
•Anything you can install on Linux or Windows (RabbitMQ,
ZeroMQ, Kafka, Kestrel, ActiveMQ, etc.)
•Any relational or NoSQL database
•Azure Tables - Simple REST NoSQL store with a twist
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22. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Solutions
•Long term storage and display retrieval: Azure Table
•Since Node.js app already used it, use Service Bus to store
changes in status for consistency
•Have daemons pull incoming status changes out and write
them to the Table
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23. Architecting with Queues - Sandy Smith - Northeast PHP 2015
New design
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__construct(EntryAccessor $mapper)
Entry
EntryAccessor
__construct($proxy, $table)
EntryAccessorTable
EntryRepository
__construct($dbh)
EntryRepositoryTable
Entries
Incoming
Daemon
Denied
Winner
Approv-
ed
In-
coming
Approved
Daemon
Denied
Daemon
Winner
Daemon

24. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Azure Table basics
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require_once 'vendorautoload.php';
use WindowsAzureCommonServicesBuilder;
use WindowsAzureCommonServiceException;
use WindowsAzureTableModelsEntity;
use WindowsAzureTableModelsEdmType;
// Create table REST proxy.
$tableRestProxy = ServicesBuilder::getInstance()->createTableService($connectionString);
try {
// Create table.
$tableRestProxy->createTable("mytable");
} catch(ServiceException $e){
// Handle exception based on error codes and messages.
}
$entity = new Entity();
$entity->setPartitionKey("pk");
$entity->setRowKey("1");
$entity->addProperty("PropertyName", EdmType::STRING, "Sample");
try {
$tableRestProxy->insertEntity("mytable", $entity);
} catch(ServiceException $e){
// Handle exception based on error codes and messages.
}

25. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Create and send with Service Bus
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use WindowsAzureServiceBusModelsQueueInfo;
use WindowsAzureCommonServiceException;
use WindowsAzureCommonServicesBuilder;
$serviceBusRestProxy = ServicesBuilder::getInstance()-
>createServiceBusService($connectionString);
try {
$queueInfo = new QueueInfo("myqueue");
$serviceBusRestProxy->createQueue($queueInfo);
} catch(ServiceException $e) {
// handle error
}
try {
// Create message.
$message = new BrokeredMessage();
$message->setBody("my message");
// Send message.
$serviceBusRestProxy->sendQueueMessage("myqueue", $message);
} catch(ServiceException $e) {
// handle error
}

26. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Receive with Service Bus
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use WindowsAzureServiceBusModelsQueueInfo;
use WindowsAzureCommonServiceException;
use WindowsAzureCommonServicesBuilder;
$serviceBusRestProxy = ServicesBuilder::getInstance()-
>createServiceBusService($connectionString);
try {
// Set the receive mode to PeekLock (default is ReceiveAndDelete).
$options = new ReceiveMessageOptions();
$options->setPeekLock(true);
// Receive message.
$message = $serviceBusRestProxy->receiveQueueMessage("myqueue", $options);
echo "Body: ".$message->getBody()."<br />";
echo "MessageID: ".$message->getMessageId()."<br />";
// *** Process message here ***
// Delete message.
$serviceBusRestProxy->deleteMessage($message);
} catch(ServiceException $e){
// handle error
}

27. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Benefits
•Queues add safety: if processing fails, main store is unchanged
•App doesn’t wait for process-update-delete cycle
– Concerns more separated
– Scaling is simpler
•Can move queue processing to separate machines
•Trivial to move to different stores for each status
•Very performant with up-to-second data
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28. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Challenges
•No full ACID
•Safety is largely in the application layer
•Potential for race conditions
– Humans suck
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29. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Takeaways
•Look for more than just long processes
•Use queues to decouple functionality
•Look for status changes, e.g. workflow
•Is the type of data the most important aspect of your data?
– It usually is!
•Design for replacement of components
– Makes changes easier (not easy)
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30. Architecting with Queues - Sandy Smith - Northeast PHP 2015
Links
•Azure: http://azure.microsoft.com/en-us/
•Social Contest:
https://github.com/MusketeersMe/SocialContest
•Me
– @SandyS1
– http://phparch.com/
•Feedback! https://joind.in/14720
•php[world] (Nov 16–20) world.phparch.com
•Slides will be at: slideshare.net/SandySmith
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