Beyond the buzzword: a reactive web-appliction in practice

Beyond the buzzword:
a reac%ve web applica*on in prac*ce
Manuel Bernhardt - @elmanu
Enterprise Java User Group Linz - September 2016
Enterprise JUG September 2016 Linz - manuel.bernhardt.io - @elmanu

Agenda
1. Reac've applica'ons: why, what
2. Small Reac've Web Applica'on
3. Deployment & Load tes'ng
If you have a ques-on, shoot!

Manuel Bernhardt
• I help mid-sized telecommunica4ons
and technology companies ge7ng
started with reac4ve microservice-
based systems to speed up and scale IT
delivery
• h=p://manuel.bernhardt.io

Reac%ve applica%ons: why, what

Root cause 1:
evolu&on of so+ware architecture

"Good old days" architecture

"3 $er" architecture

"Cloud" architecture

"Microservices" architecture

=> Increasing amount of network I/O

Root cause 2: evolu.on of hardware

Why reac)ve ?
1. Distributed systems are the rule, not the excep1on
2. Programming needs to acknowledge the existance of many
hardware threads, the lost opportunity of not using it & the cost
of locking

What reac)ve ?

Reac%ve systems are distributed
systems
(they're a subset thereof)

What's the main diﬀerence between
a distributed system and a non-
distributed system?

What's the main diﬀerence between
a distributed system and a non-
distributed system?
Distributed systems fail much more
o-en (and in much stranger ways)
than non-distributed ones

Failure
Failure is a ﬁrst-class ci.zen in reac.ve
systems. They're designed for failure.

Handling failure

Handling failure
• checked excep*ons are a terrible idea in the context of reac*ve /
distributed systems
• languages, tools and pa<erns for streamlining failure handling:
Func*onal Programming, Futures, Message Passing

Don't try to hide the network!
• CORBA, RPC & friends: trying to abstract away the network
• what happens when the network call
• ... fails
• ... is slow
• ... is some%mes slow
• ... someAmes fails, someAmes doesn't

Don't try to hide the
network!
• ignoring of the Fallacies of Distributed
Compu8ng (Deutsch & Gosling)
• ignoring the CAP theorem

Reac%ve architectural pa/ern
h"p://www.reac,vemanifesto.org

Reac%ve Systems - Conclusion
• Reac&ve Systems are designed for failure
• Reac&ve Systems are distributed, replicated accross several
nodes (can scale up and down)

Let's build a small Reac0ve Web
Applica0on

Actors
• lightweight objects
• send and receive messages (mailbox)
• can have children (supervision)
"Long-lived" async computa5on

CODING

Futures
scala.concurrent.Future[T]
• holds a value of type T
• can either fail or succeed
• async code does not block a thread
while wai8ng for comple8on
"Short-lived" async computa6on

Pipe
akka.pattern.pipe
• bridge between Futures and Actors
• implemented as anonymous actor

Circuit Breaker
akka.pattern.CircuitBreaker
• helpful when dealing with legacy / slow
systems & prevents cascading failure
• like an electric circuit breaker, trips
when there's a surge
• trips a=er a given number of failures, for
a given >meout, then a?empts reset

Deployment

Deployment
• stand-alone vs. "elas/c deployment"
• elas/c, fault-tolerant is not trivial
• use a managed service / solu/on

Deployment
• Lightbend ConductR
• automated cluster management for
Play / Akka / ... applica>ons
• automated node failure & network
par++on resolu+on

Deployment
• fully managed opera0ons
• auto scalability feature (horizontal &
ver0cal)
• a<rac0ve pricing

Load tes)ng

Gatling
• open-source load tes0ng framework
• built with Scala, Akka and Ne=y
• two phases: record and run

Gatling simula,on ﬁle
// ...
setUp(
scn.inject(
nothingFor(4 seconds),
rampUsers(100) over(10 seconds),
atOnceUsers(10),
constantUsersPerSec(2) during(15 seconds) randomized,
splitUsers(500) into (
rampUsers(50) over(10 seconds)
) separatedBy(2 seconds)
).protocols(httpProtocol)
)

Bees with machine guns

Configuring all the things
• Installing Python & bees with machine
guns
• AWS console (keys, security group w/
SSH access)
• boto config file

Conﬁguring all the things
~/.boto
[Credentials]
aws_access_key_id = foobar1
aws_secret_access_key = foobar2
[Boto]
debug = 2

A"ack!

Thank you!
Ques%ons & Comments ?
• h#p://manuel.bernhardt.io
• manuel@bernhardt.io
• @elmanu

Beyond the buzzword: a reactive web-appliction in practice

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