building reactive applications with akka
Post on 02-Jul-2015
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Building Reactive applicationsusing Akka
Nilanjan Raychaudhuri@nraychaudhuri
Reactive Applications
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@nraychaudhuri
Essence of Reactive applications
Reactive Traits
Akka is enabler of Reactive applications
Reactive Applications
• Individual entities that can only communicate by passing messages
• Excellent for isolating mutable state and protecting it without locks
• Location transparency for remote and clustered topologies
• Supervision
• Well-suited for creating state machines
• Fault tolerance via Supervision
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Reactive Applications
Reference Architecture
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Play Server
Play Server
Play Server
Play Server
Web Tier (Play) Work Tier (Akka)
Akka Master Router
Akka Router Standby
Akka Worker
Akka Worker
Akka Worker
Akka Worker
Akka Worker
responsive event drivenscalableresilient
Message-driven
Reactive applications are architected based on loosely coupled design
Reactive Applications
Message-Driven• Loosely coupled architecture, easier to extend, maintain, evolve
• Asynchronous and non-blocking• Concurrent by design, immutable state• Lower latency and higher throughput
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“Clearly, the goal is to do these operations concurrently and non-blocking, so that entire blocks of seats or sections are not locked.
We’re able to find and allocate seats under load in less than 20ms without trying very hard to achieve it.”
Andrew Headrick, Platform Architect, Ticketfly
Introducing Actor Model
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A computational model that embodies:
✓ Processing
✓ Storage
✓ Communication
Supports 3 axioms—when an Actor receives a message it can:
1.Create new Actors
2.Send messages to Actors it knows
3.Designate how it should handle the next message it receives
Actor model
Thread pool
Actor modelActor model
Actor Actor
Akka actor -‐ Definition
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Akka actor -‐ Create
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Akka actor -‐ Send
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Elastic
Reactive applications scale up and down to meet demand
Elastic• Scalability and elasticity to embrace the Cloud
• Leverage all cores via asynchronous programming• Clustered servers support joining and leaving of nodes• More cost-efficient utilization of hardware
“Our traffic can increase by as much as 100x for 15 minutes each day. Until a couple of years ago, noon was a stressful time.
Nowadays, it’s usually a non-event.”
Eric Bowman, VP Architecture, Gilt Groupe
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FlightSearchActor
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FlightSearch Actor - I
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FlightSearch Actor - II
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FlightSearchActor
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SearchWorker - I
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SearchWorker - II
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ProviderProxyActor
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ProviderProxy - I
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ProviderProxy - II
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Flight search flow
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Let it crash
Reactive applications are architected to handle failure at all levels.
Resilient• Failure is embraced as a natural state in the app lifecycle
• Resilience is a first-class construct• Failure is detected, isolated, and managed• Applications self heal
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“The Typesafe Reactive Platform helps us maintain a very aggressive development and deployment cycle, all in a fail-forward manner.
It’s now the default choice for developing all new services.”
Peter Hausel, VP Engineering, Gawker Media
Failure?
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Think Vending Machine
Coffee MachineProgrammer
Inserts coins
Gets coffee
Add more coins
Think Vending Machine
Coffee MachineProgrammer
Service Guy
Inserts coins
Gets coffee
Out of coffee beans
error
Adds more beans
Think Vending Machine
Out of coffee beans errorWrong
The Right Way
ServiceClient
Supervisor
Request
Response
Validation Error
Application Error
Manages Failure
Supervision
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A
B
BarFoo
C
BE
A
C
system.actorOf(Props[Foo], “Foo”)
context.actorOf(Props[A], “A”)
Actor Topology
OneForOne
AllForOne
Reactive Applications
Isolate failure at all levels• Within one node
• Across many nodes (JVMs)
• Across many physical servers
• Across data centers
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Scale out
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Akka clustering
Reactive Applications
IoT
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Reactive Applications
Precision Farming
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Akka ClusterJournal
Code
Q & Option[A]
@nraychaudhuri
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