RedisAs a Message Queue

1Wednesday, October 9, 13

The Plug

Essentially, a screenshot site

MMORPG (Massively-Multiplayer, Online Role-Playing Game) niche market

Site visitors browse games, games have albums

Players can upload screenshots

2Wednesday, October 9, 13

The Architecture(2) 6-core CPU, 16GB RAM, 6-drive 3TB RAID10

(1) 8-core CPU, 16GB RAM, 2-drive 64GB RAID1 SSD, 2-drive 320GB RAID1

(2) layer-4 ipvsadm load balancers in master/backup failover via keepalived

(3) PostgreSQL master/slave database

(3) nginx+php-fpm (5.5) app servers

Replicated file system via GlusterFS for images

Memcached instance for php sessions

Redis for caching and message queue

Amazon Cloudfront for CDN (content delivery network)

PhalconPHP framework, Gmagick, Twitter Bootstrap v3.0, REST API

3Wednesday, October 9, 13

Message Queue?

Push messages into a stack

Pop (pull) messages off a stack

You put (push) data (messages) into the queue (stack)

Messages are things you want to process later by pulling them from the queue

4Wednesday, October 9, 13

Messages?

A “message” is just some data

Could be an array

Could be a string

5Wednesday, October 9, 13

The Use-Case

When a user uploads images, it is bad to block the user while your server processes the photos

Image resizing

Creating multiple versions

Creating database entries

6Wednesday, October 9, 13

The User Flow

User selects images

Images are uploaded to app server

App server generates a UUID filename and copies the images to the replicated file system

App server increments a Redis counter

App server creates an array with uuid, user id, game id and pushes this “message” into the Redis list (message queue)

7Wednesday, October 9, 13

Batch Processing

A separate PHP/other process running on any of the app servers (crontab, forking daemon) pops the Redis list to get a message

By using GlusterFS as a replicated file system all app servers have all the uploads/images

When a message is obtained from Redis queue, it processes the file upload, creates various image sizes

Creates a database entry in PostgreSQL

8Wednesday, October 9, 13

Lets push!// Create a new redis connection$r = new Redis();$r->connect($host, $port);

// Create the message array$message = [‘uuid’ => $uuid, ‘userId’ => $userId, ‘gameId’ => $gameId];

// Get a new message id by implementing the builtin increment feature of Redis$id = $r->incr('mmoscreens:screens-queue');

// Push the id into the queue (Redis list)$r->lpush('mmoscreens:screens-queue', $id);

// Set the $message into Redis$r->hmset("mmoscreens:screens-queue:$id", $message);

9Wednesday, October 9, 13

Lets pull!// Create a new redis connection$r = new Redis()->connect($host, $port);

// pop the message ID from the queue, or block until one is available$id = $r->brPop('mmoscreens:screens-queue', BLOCK_WAIT_TIME);

// brPop returns [listName, element]isset($id[1]) && $id = $id[1];

// Get the message from Redis$message = $r->hgetall("mmoscreens:screens-queue:$id");

$message:[

‘uuid’ => ‘fef4430c-e4a8-4874-b380-63edd2fa8472’,‘userId’ => 10611,‘gameId’ => 8

]10Wednesday, October 9, 13