Architecting with Queues for Scale, Speed, and Separation (DCPHP 3/11/15)

Architecting with Queues for
Scale, Speed and Separation
Sandy Smith
DCPHP 3/11/15

Architecting with Queues - Sandy Smith - DCPHP - 3/11/15
The Challenge
2

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
3

Stretch goals
•Allow any size contest
•Assume global contest with distributed moderators
4

Initial design
5

The real bottleneck
What’s the slowest and
most variable part of any
application?
6

Insert Text Here
The real bottleneck
7

Quick refresher
Performance vs. Scaling

Vertical vs. Horizontal Scaling
8

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
9

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
10

Worst of all…
•This design really didn’t show oﬀ all the stuﬀ in Azure
11

(We had a week left)
Redesign time
12

Redesign goals
•Include as much Azure stuﬀ as is reasonable
•Implement the stretch goals of scalability
13

Queues to the rescue!
(Plus some other cool stuﬀ)
14

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
15

Azure queuing options
Azure Queues (duh)
•Simple
•“Short”-lived (<7 days)
•Used within Azure
•Uses REST
•Can track message
processing
16
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

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
17

Solutions
•Long term storage and display retrieval: Azure Table
•Since entries could begin long before a conference, use
Service Bus to store changes in status
•Have daemons pull incoming status changes out and write
them to the Table
18

New design
19

Azure Table basics
20
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); 
// Handle exception based on error codes and messages. 
}

Create and send with Service Bus
21
use WindowsAzureServiceBusModelsQueueInfo; 
 
$serviceBusRestProxy = ServicesBuilder::getInstance()-
>createServiceBusService($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 
}

Receive with Service Bus
22
use WindowsAzureServiceBusModelsQueueInfo; 
 
$serviceBusRestProxy = ServicesBuilder::getInstance()-
>createServiceBusService($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); 
// handle error 
}

Benefits
•Queues add safety: if processing fails, main store is unchanged
•App doesn’t wait for process-update-delete cycle
– Concerns more separated

•Can move queue processing to separate machines
•Trivial to move to diﬀerent stores for each status
•Very performant with up-to-second data
23

Challenges
•No full ACID
•Safety is largely in the application layer
•Potential for race conditions
– Humans suck
24

Takeaways
•Look for more than just long processes
•Use to decouple functions
•Look for status changes
•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)
25

Links
•Azure: http://azure.microsoft.com/en-us/
•Social Contest: 
https://github.com/MusketeersMe/SocialContest
•Me
– @SandyS1

– http://phparch.com/

•Feedback! https://joind.in/event/dc-php-march-2015
•Lone Star PHP (April 16–18): http://lonestarphp.com
•php[tek] (May 18–22) http://tek.phparch.com
•Slides will be at: http://www.slideshare.net/SandySmith
26

Image credits
•Questions? by Valerie Everett 
https://ﬂic.kr/p/5zEjFG
•Expanded coke zero can! by Audin Malmin 
https://ﬂic.kr/p/5Ldjx8
27

Architecting with Queues for Scale, Speed, and Separation (DCPHP 3/11/15)

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