Workshop: Introduction to the Disruptor

An Introduction to the LMAX DisruptorTrisha Gee, Developer at LMAX Exchange

@trisha_geemechanitis.blogspot.com

Tuesday, 25 September 12

Laptop Setup... Go!


The Disruptor?


The Workshop

• Introduction to the Disruptor

• Simplest Case

• Performance Results

• Going Parallel

• The Real World

• Questions


What is The Disruptor?

• Very fast message passing

• Data structure and work flow without contention

• Allows you to go truly parallel


So...?


The Magic RingBuffer












The Events are Buckets


I’ve got a RingBuffer!

• Erm.... how do I poke things into it?


The Publisher








...so now I want to read

• The Disruptor provides nice batching behaviour for free


BatchEventProcessor
















The Problem


Tower Defence?







Exercise OneOne publisher, one event handler


Our Problem


Simplest Disruptor


• Print status of the enemy when the tower sees it

• Print status of enemy after the tower shoots it

• Shoot all enemies

TODO


Task Breakdown

• Wire up the EventTranslator & EventHandler, using the Disruptor class

• Implement shootAt

• Implement respawn & isDead

• Get unit tests to pass

• (check out mechanitis.examples.disruptor)


Exercise One Goals

1. Understand the roles of Translators and Event Handlers

2. Understand how to wire up a simple Disruptor configuration

3. Understand how to get events flowing through the Disruptor


Performance vs a Queue

Mac Air, 1.7GHz Core i5:run 0: BlockingQueue=3,390,060 Disruptor=69,108,500 ops/secrun 1: BlockingQueue=5,229,851 Disruptor=71,123,755 ops/secrun 2: BlockingQueue=4,303,481 Disruptor=65,530,799 ops/sec

Disruptor - Time Taken: 3,242 millisDisruptor - Time Taken: 3,319 millisDisruptor - Time Taken: 4,045 millis

Queue - Time Taken: 30,022 millisQueue - Time Taken: 31,823 millisQueue - Time Taken: 29,280 millis


Exercise TwoOne publisher, two parallel event handlers


Let’s log all the enemies


Parallel Processors


• Make each enemy unique

• Write the details of each enemy generated into a text file


Task Breakdown

• Add randomness to enemy (e.g. give them a speed to travel at)

• Wire in the EnemyLogger

• Implement describeTo in enemy


Exercise Two Goals

1. Understand that EventHandlers can process in parallel

2. Understand how to wire up EventHandlers in parallel

3. Understand the caveats to going parallel - single writer principal


Exercise ThreeDiamond Dependencies


Recording the Results


Sequence Barriers


Managing Dependencies


• Don’t use the Disruptor Wizard for configuration

• Record results of the game to a different text file

• Optional: add variability to Turret


Task Breakdown

• Remove use of Disruptor.java and wire up manually (mechanitis.examples.disruptor)

• Wire in ResultHandler

• Add missing things from Enemy class


Exercise Three Goals

1. Understand sequence barriers

2. Understand different dependency configurations

3. Understand wiring up without the wizard


Exercise FourPlaytime!!


Slow Consumers?


The Real World





Ticket Purchasing









Other Uses

• Queue replacement

• Single-threading your code

• Filtering

• Coalescing

• Dependency graphs


Questions


Technology

Workshop: Introduction to the Disruptor