Do you queue

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

Kevin Schroeder
Technology Evangelist for Zend
Programmer
Sys Admin
Author
IBM i Programmer’s Guide to PHP
You want to do WHAT with PHP?
Race Ferraris on the weekend
My Honda has a dismal win record
About me

I blog at eschrade.com
Follow us!
(good things will happen to you)
Zend Technologies
http://twitter.com/zend
http://twitter.com/kpschrade (me!)

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

Performance
Execute logic apart from the main request (asynchronicity)
Scalability
The ability to handle non-immediate logic as resources are available
Why would you want to queue?

People often say that performance and scalability are two completely different things.
This is inaccurate
Performance is the speed by which a request is executed
Scalability is the ability of that request to maintain its performance as load/infrastructure increases
Performance & Scalability

DON’T!!
You are not Facebook
You probably won’t be
Don’t overcomplicate your problems by trying to be
So how do you scale to Facebook size?

Typical anatomy of a PHP Application
Bad for scala-bility!
Presentation
Application Control
Database Access
Business Logic
Presentation
Application Control
Business Logic
Presentation
| 8

Good for Scalability
Presentation
Something.phtml
Something.phtml
Something.phtml
Something.phtml
Something.phtml
Something.phtml
Something.phtml
Something.phtml
Application Control
Something.php
Something.php
Something.php
Something.php
Something.php
Something.php
Something.php
Something.php
Business Logic
Something.php
Something.php
Something.php
Something.php
Something.php
Something.php
Something.php
Something.php
Database Access
Something.php
Something.php
Something.php
Something.php
Something.php
Something.php
Something.php
Something.php
| 9
| 3-Nov-10

Defined tasks
Loose coupling
Resource discovery
What helps make software scalable?

The Golden Rule of Scalability
“It can probably wait”

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Data is “out of date” once it leaves the web server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
Asynchronous execution uses

A sledgehammer can hit a machine
Scalability and High Availability are yin and yang
A site that can’t keep running is not scalable
A site that can’t scale will fail (if it gets really popular)
Machines can be added and removed at will
Not “cloudy” necessarily
No single point of failure
Data exists in at least two, preferably at least three, places
Characteristics

Waste disk space
Control usage (don’t let users do anything they want)
Pre-calculate as much as possible
Calculate and cache/store
Don’t scan large amounts of data
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)
Considerations

Use Cron /w PHP CLI (probably shouldn’t do this)
Use Gearman
Use home-grown (don’t do this)
Use pcntl_fork() (NEVER do this)
Use Zend Server Job Queue
Options

Your only real options
Very cloud friendly
* 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

Schedule jobs in the future
Set recurring jobs
Execute immediately, as resources are available (my fav)
Utilize ZendJobQueue()
Using the Zend Server Job Queue

Job Queue Architecture – Elastic Backend
Web Server /w JQ
Web Server
Users!
Web Server /w JQ
Web Server
Load Balancer
Web Server /w JQ
Web Server
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
Users!
Web Server
Web Server /w JQ
Load Balancer
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

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
Kevin’s favorite way to implement it

Q_Manager
Handles connecting to the queue and passing results back and forth
Q_JobAbstract
Abstract class that a job would be based off of
Q_Response
The response from the manager when a job is queued. Contains the server name and job number
Job_Scandir
The actual job that scans the directory
Job_ScandirResult
An object that represents the data found
Classes involved in the demo

Create job and set data
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
Client polls the manager to get a completed job
When the job is returned pass the serialized version of the executed job
Execution Flow

Let’s write some code
(no I’m not copping out with slides. We’re all told to show our work in grade scool)

Follow us!
Zend Technologies
http://twitter.com/zend
http://twitter.com/kpschrade (me!)

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

Do you queue

by Kevin Schroeder

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Do you queue

by Kevin Schroeder

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Do you queue Presentation Transcript

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