Do you queue (updated)

©All rights reserved. Zend Technologies, Inc.

Do you queue?

By Kevin Schroeder

Technology Evangelist

Zend Technologies


About Kevin

Past: Programming/Sys Admin

Current: Technology Evangelist/Author/Composer

@kpschrade


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 separate things.

This is inaccurate (consider Google)

• 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

| 7

Presentation

Application Control

Database Access

Business Logic

Presentation

Application Control

Business Logic

Presentation

Bad for scala-bility!

©All rights reserved. Zend Technologies, Inc. | Apr 12, 2023

| 8

Presentation

Database Access

Business Logic

Application Control

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Good for Scalabilit

y


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

• Pre-analysis (predicting where your users will go)

• 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Data is “out of date” once it leaves the web server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; introduces

lag

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


Gearman* Zend Server Job Queue

FreeLightweightOpen Source(mostly) language agnosticDistributed queuing

Ready to goIntegrates with Event MonitoringIntegrates with Code TracingRuns over a widely known protocolLoad distribution can be accomplished outside of the queue

Your only real options

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

Very cloud friendly

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

Users!

Web Server /w

JQ

Web Server /w

JQ

Web Server /w

JQ

Web Server

Web Server

Web Server

Load B

ala

nce

r

• Pros Scale the backend as necessary

Default (easy) mechanism

• Cons Getting the job status requires using a DB


Job Queue Architecture – Elastic Frontend

Users!

Web Server

Web Server

Web Server

Web Server /w

JQ

Web Server /w

JQ

Web Server /w

JQ

Load B

ala

nce

r

• 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


com\zend\jobqueue\Manager

Handles connecting to the queue and passing results back and forth

com\zend\jobqueue\JobAbstract

Abstract class that a job would be based off of

com\zend\jobqueue\Response

The response from the manager when a job is queued. Contains the server name and job number

org\eschrade\jobs\Scandir

The actual job that scans the directory

org\eschrade\jobs\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 skool)


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