Magento's Imagine eCommerce Conference 2011 - Do You Queue?

Do you queue?
Characteristics of
scalability
Kevin Schroeder
Technology Evangelist
Zend Technologies

© All rights reserved. Zend Technologies, Inc.

About me

Past: Programming/Sys Admin
Current: Technology Evangelist/Author/Composer
@kpschrade


I blog at eschrade.com

Follow us!
(good things will happen to you)

 Zend Technologies

 http://twitter.com/zend

 http://twitter.com/kpschrade (me!)


Twtpoll results

Could your PHP apps benefit from being able to
process data or execute asynchronously?


Why would you want to queue?

• Performance
 Execute logic apart from the main request (asynchronicity)

• Scalability
 The ability to handle non-immediate logic as resources are
available


Typical anatomy of a PHP Application

Presentation
Application Control

Bad for
Database Access

Business Logic

scala- Presentation

Application Control

bility!
Business Logic
Presentation

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© All rights reserved. Zend Technologies, Inc. 6

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Application Control
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Scalability
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What helps make software scalable?

Defined tasks
Loose coupling
Resource discovery


The Golden Rule of Scalability
“It can probably wait”


Asynchronous execution uses

• Pre-caching data
• Data analysis
• Data processing
• Pre-calculating (preparing data for the next request)

Data is “out of date” once it leaves the web server
Immediacy is seldom necessary


Considerations

• Waste disk space
• Control usage (don’t let users do anything they want)
• Pre-calculate as much as possible
 Calculate and cache/store

• Keep data processing off the front end servers
• Don’t just cache
 Don’t let it substitute for thought

 Cache hit rates can be meaningless if you have hundreds of cache
hits for a request


Considerations

• Build a deployment mechanism with NO hardcoded values
like directory or resource locations
• Make as much as possible configurable/discoverable
• Decouple/Partition
 Don’t tie everything (relationships and such) into the database

• Use queues/messaging
 Stomp interfaces are really good for PHP – Can also use Java
Bridge
 Zend_Queue has several interfaces

• Try to use stateless interfaces
 (polling is more scalable than idle connections)

Options

• Use Cron /w PHP CLI (not the best idea)
 People mostly use cron simply due to availability
• It’s an available option, not necessarily the best option.

• Use Gearman
• Use home-grown (don’t do this)
• Use pcntl_fork() (NEVER do this)
• Use Zend Server Job Queue


Your only real options

Gearman* Zend Server Job Queue
Free Ready to go
Lightweight Integrates with Event Monitoring
Open Source Integrates with Code Tracing
(mostly) language Runs over a widely known protocol
agnostic Load distribution can be Very cloud friendly
Distributed queuing accomplished outside of the queue

* I am not an expert on Gearman. Corrections will be taken in the spirit that they are given.

For obvious reasons, I will focus on Zend Server


What the heck is Zend Server?
Zend Server

Application Reliability & Scale-Out Business-grade
Performance Management PHP

Acceleration Monitoring Clustering Hot Fixes

Optimization Root-Cause Job Queue Support

Caching Configuration Downloads Java Bridge

Zend Framework

PHP

Linux Windows IBM i
(rpm/web repositories) (MSI) (PTF)

15 Zend Server © All rights reserved. Zend Technologies, Inc.

Job Queue Architecture – Elastic Backend

Web Server
Web Server
/w JQ

Load Balancer
Web Server
Users! Web Server
/w JQ

Web Server
Web Server
/w JQ

• Pros
 Scale the backend as necessary

 Default (easy) mechanism

• Cons
 Getting the job status requires using a DB


Job Queue Architecture – Elastic Frontend

Web Server
Web Server
/w JQ

Load Balancer
Web Server
Users! Web Server
/w JQ

Web Server
Web Server
/w JQ

• Pros
• Easy to communicate with the Job Queue server handling the job

Cons
• Requires you to build your own interface (or just use mine!)


Kevin’s favorite way to implement it

• Create a task-handling controller
• Create an abstract task class
 Understands the Job Queue

 Self contained
• If Elastic Backend: connects to localhost
• If Elastic Frontend: connects to load balancer (my preferred), load
balanced JQ servers manage themselves

• Execute the task, have it serialize itself and send it to send
to the task handler


Classes involved in the demo
 Manager
Handles connecting to the queue and passing results back and forth
 JobAbstract
Abstract class that a job would be based off of
 Response
The response from the manager when a job is queued. Contains the
server name and job number
 GetRemoteLinks
• Scans a given web page and reports back a list of all the links on the
page


Execution Flow
1. Create job and set data
2. Execute job
• Job passes itself to the queue manager
• Manager serializes job
• Manager uses HTTP call through a load balancer to queue the job
• The queue on the other end returns the job id and server name
• Job ID and server name is passed to the client
3. Client polls the manager to get a completed job
• When the job is returned pass the serialized version of the executed
job


Demo


Neato, but how in the world
does this pertain to Magento?


How?

• Long running front-end requests kill front-end
responsiveness which kills the user experience
 40% will wait no more than 4 seconds for a website (Forrester)

• Calculating cache data on-the-fly can lead to bad user
experiences (abruptly slow page load times) and
consistency problems
• Long running page requests can push up against
max_execution_time
 For example, handling payments from a slow CC API

 Simply setting it to run longer is a band-aid on a broken bone


Solution?

1. Build Zend Server integration extensions
 Zendserver_Jobqueue
 Zendserver_Monitor
2. Utilize the event system to intercept actions
 Async_Payment (for payments, in this case)
3. Profit! (scalability AND performance, actually)


Building a job

• Install the Zend Server Magento extension
• Create a class that extends
Zendserver_Jobqueue_JobAbstract
• Call $job->execute();


Payment as an example

• Hooks an observer into
controller_action_predispatch_checkout_onepage_saveOrder, core_block_abstract_to
_html_after

• Checks if a defined template is being rendered
• Injects JavaScript that changes the review.save() method
• Injects a new URL for submitting the transaction which
creates a job
 Passes POSTed data to a job

• Job executes by submitting the payment URL on behalf of
the browser, storing the result
• Browser pings the server to see if the job has completed
executing yet

Scaling the solution

Webserver Job Queue/
Webserver

Load Balancer
Webserver

Webserver

* Duplicate deployments on
ALL machines
Database or
Session
Clustering


Downloads

• Zend Server
 http://www.zend.com/server
http://bit.ly/hWJBYw
• Zendserver_Jobqueue
 https://github.com/kschroeder/Magento-ZendServer-JobQueue

• Zendserver_Monitor
 https://github.com/kschroeder/Magento-ZendServer-Monitor

• Async_Payment
 https://github.com/kschroeder/Magento-Async-Payment

• Job Queue library & demo
 https://github.com/kschroeder/ZendServer-JobQueue-Job-API


Magento/Zend Case Study - http://bit.ly/horpFF

Follow us!

 Zend Technologies

 http://twitter.com/zend

 http://twitter.com/kpschrade (me!)


Get this information and all the
examples at eschrade.com…


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