Actors Unleashed: Reactive Systems, DDD, and the Ubiquitous … · 2017-06-02 · What Donald Knuth...
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Actors Unleashed: Reactive Systems, DDD, and the Ubiquitous Language @VaughnVernon Copyright © 2012-2017 for{comprehension} All rights reserved.
Transcript of Actors Unleashed: Reactive Systems, DDD, and the Ubiquitous … · 2017-06-02 · What Donald Knuth...
Actors Unleashed: ReactiveSystems, DDD, and theUbiquitous Language
@VaughnVernonCopyright © 2012-2017 for{comprehension} All rights reserved.
Rear AdmiralGrace Hopper
and the nanosecond...
Donald Knuth
“Premature optimization is the root of all evil.”
WhatDonald KnuthActually Said:
“We should forget about small efficiencies,say about 97% of the time: prematureoptimization is the root of all evil. Yet weshould not pass up our opportunities in thatcritical 3%.”
AndDonald Knuth
Also Said:“People who are more than casuallyinterested in computers should have at leastsome idea of what the underlying hardware islike. Otherwise the programs they write willbe pretty weird.”
Objects
1973 - 2003
Cores Matter
More cores, not (much) faster cores
Threading Is Easy!
Threading Is Hard!
Actor Model
Alan Kay: “The big idea is messaging...”
Dr. Carl Hewitt
Carl Hewitt, 1973
Joe Armstrong, Erlang
1986
Jonas Bonér, Akka
2009
José Valim, Elixir
2011
Actors AreReactive
Reactive Is
Reactive Is
Reactive Is
Reactive Is
Why the Actor Model Now?
#IoT
Because Cores
88 / 200+ cores with Xeon Phi co-processors
EmbraceLatency
MoreWithLess
Direct Asynchronous Messaging
Lock-Free, Share Nothing
Become:Prepare for Next Message
Actor System
Actor Concurrency
How Many Actors?
50+
100+
1,000,000+
Typical Architecture
Complexity Stack
Simplicity Stack
Eric Evans, DDD
Essence of DDD
Context Mapping
Responding to RapidNew Business Direction
DDD enables necessaryknowledge crunching
Actors and messages enablesrapid implementation and
clear understanding
Actors and DDD
Alan Kay: “The big idea is messaging...”
Alan Kay: “The Actor model retained moreof what I thought were the good
features of the object idea.”
UbiquitousLanguageAs Actors and messages...
Actor
Command Event
Actor
Command Event
Event StormingTime
Use design-level storming
Aggregates
Transactional Consistency Boundary
Aggregate
● Immutable state object/record
Implementation
● Transition and replace stateupon command/event
● Emit corresponding event
class Product(productId: String) extends PersistentActor {
override def persistenceId = productId var state: Option[ProductState] = None override def receiveCommand: Receive = { case c: CreateProduct =>
val event = ProductCreated(productId, c.name, ...)
persist(event) { persistedEvent => updateWith(persistedEvent) sender ! CreateProductResult(productId, c.name, ...) } ... } override def receiveRecover: Receive = { case e: ProductCreated => updateWith(e) ... } def updateWith(e: ProductCreated) { state = Option(ProductState(e.name, e.description, false, None)) }}
val product = Product.newInstance()
product ! CreateProduct("Weeble", "A weeble.")
Client
Reactive Systems
Welcome,Uncertainty!
Fortress
Activity
Model
Resources
https://github.com/VaughnVernon/DDDwithActors
