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the
Agenda
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101
Reactive
Programming
types &
operators
Reactor 3
and Spring
Reactor
debugging
testing
and
other beasts
backpressure
and
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101
Reactive
Programming
types &
operators
Reactor 3
and Spring
Reactor
debugging
testing
and
reactor-netty
other beasts
backpressure
and
reactor-kafka...
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Reactive Programming 101
what does it bring to the table?
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WHY?
because blocking is evil
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sync/blocking
main thread processing
resumes
I/O
BAD
! app does
nothing
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async & blocking
main thread wait &
join
! new
threads,
costly
! complex
BAD
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async & nonblocking
“event loop”
in non-blocking
processing
chunks
no more threads
than needed
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how do you achieve that
without losing your mind ?
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Reactive Programming
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Composing asynchronous
& event-based sequences,
using non-blocking operators
“
”
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without sacrifice
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without sacrifice
Callbacks ?
Futures ?
easy to block
hard to compose
callback hell !
not readable
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Pull? Push!
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Pull? Push!
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Pull? Push!
(or actually a little bit of Both)
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vs
Iterable
-
Iterator
Publisher
-
Subscriber
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Data in Flux
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Publisher Subscriber
push events
produces consumes
feedback
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interfaces from
Reactive Streams
spec
Publisher Subscriber
feedback
consumes
push events
produces
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Publisher Subscriber
push events
produces consumes
feedback
Subscriber
onNext(T)
onComplete();
onError(Throwable);
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Publisher Subscriber
produces consumes
feedback
0..N elements
+
0..1 (complete | error)
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Publisher Subscriber
push events
produces consumes
feedback
backpressure
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Publisher Subscriber
push events
produces consumes
feedback
can I have an
API though?
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Publisher Subscriber
push events
produces consumes
feedback
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Reactor 3
types and operators
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Flux
for 0..N elements
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Mono
for at most 1 element
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Reactive Streams
all the way
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focus on Java 8
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focus on Java 8
Duration, CompletableFuture, Streams
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an Rx-inspired API
with a vocabulary of operators similar to RxJava...
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an Rx-inspired API
...but not exactly the same
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Flux/Mono
generator
operator
operator
operator
nothing
happens
until you
subscribe
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Flux/Mono
generator
Subscriber
operator
operator
operator
nothing
happens
until you
subscribe
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Flux/Mono
generator
Subscriber
operator
operator
operator
per
Subscription
state
Sub
Sub
Sub
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Flux/Mono
generator
Subscriber
operator
operator
operator
data
flows
Sub
Sub
Sub
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examples
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Flux.range
Subscriber
map
filter
buffer
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Flux.range(5, 3)
.map(i -> i + 3)
.filter(i -> i % 2 == 0)
.buffer(3)
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Flux.range
Subscriber
map
filter
buffer
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Flux.range
Subscriber
map
filter
buffer
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Flux.range
Subscriber
map
filter
buffer
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Flux.range
Subscriber
map
filter
buffer
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Flux.range
Subscriber
map
filter
buffer
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Flux.range
Subscriber
map
filter
buffer
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Flux.range
Subscriber
map
filter
buffer
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Flux.range(5, 3)
.map(i -> i + 3)
.filter(i -> i % 2 == 0)
.buffer(3)
5, 6, 7 |
8, 9, 10 |
8, 10 |
[8,10]|
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Flux.from
Subscriber
map
filter
retry
Publisher from
HTTP reactive
client
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Flux.from
Subscriber
map
filter
retry
Publisher from
HTTP reactive
client
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Flux.from
Subscriber
map
filter
retry
Publisher from
HTTP reactive
client
resubscribe
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go DEEPER!
async sub-processes with flatMap
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flatMap(user -> tweetStream(user))
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flatMap(user -> tweetStream(user))
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flatMap(user -> tweetStream(user))
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flatMap(user -> tweetStream(user))
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& much
more...
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threading
contexts
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Reactor
is
agnostic
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however it
facilitates switching
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Schedulers
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Schedulers
elastic, parallel, single, timer...
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publishOn
switch rest of the flux on a thread
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subscribeOn
make the subscription and request happen
on a particular thread
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Flux/Mono
generator
operator
subscribeO
n
operator
publishOn
operator
operator
Subscriber
Sub
Sub
Sub
Sub
Sub
Sub
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Flux/Mono
generator
operator
subscribe
On
operator
publish
On
operator
operator
Subscriber
Sub
Sub
Sub
Sub
Sub
Sub
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Flux/Mono
generator
operator
subscribeO
n
operator
publishOn
operator
operator
Subscriber
Sub
Sub
Sub
Sub
Sub
Sub
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Flux/Mono
generator
operator
subscribeO
n
operator
publishOn
operator
operator
Subscriber
Sub
Sub
Sub
Sub
Sub
Sub
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Flux/Mono
generator
operator
subscribeO
n
operator
publishOn
operator
operator
Subscriber
Sub
Sub
Sub
Sub
Sub
Sub
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Flux/Mono
generator
operator
subscribeO
n
operator
publishOn
operator
operator
Subscriber
Sub
Sub
Sub
Sub
Sub
Sub
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Testing & Debugging
in an asynchronous world
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Testing a Publisher
StepVerifier
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Testing a Publisher
with Virtual Time support
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Simulate a source
TestPublisher
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Debugging Issues
stacktraces get hard to decipher
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usually just show
where Subscription happens
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java.lang.IndexOutOfBoundsException: Source emitted more than one item
at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(MonoSingle.java:120)
at
reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:314)
...
...
at reactor.core.publisher.Mono.subscribeWith(Mono.java:2668)
at reactor.core.publisher.Mono.subscribe(Mono.java:2629)
at reactor.core.publisher.Mono.subscribe(Mono.java:2604)
at reactor.core.publisher.Mono.subscribe(Mono.java:2582)
at reactor.guide.GuideTests.debuggingActivated(GuideTests.java:727)
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Find where the Flux
was instantiated (assembly)
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Checkpoint()
or full assembly tracing
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costly!
Checkpoint()
or full assembly tracing
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Assembly trace from producer [reactor.core.publisher.MonoSingle] :
reactor.core.publisher.Flux.single(Flux.java:5335)
reactor.guide.GuideTests.scatterAndGather(GuideTests.java:689)
reactor.guide.GuideTests.populateDebug(GuideTests.java:702)
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BACKPRESSURE
and other beasts
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Publisher Subscriber
subscribe
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Publisher Subscriber
push data as fast as possible
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Publisher Subscriber
subscribe
with small request
(eg. 1)
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Publisher Subscriber
1 onNext
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Publisher Subscriber
request more
(eg. 2)
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Publisher Subscriber
2 onNext
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Publisher Subscriber
backpressure
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other ways of dealing with backpressure
eg. drop, buffer...
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internal
optimisations
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macro FUSION
avoids unnecessary request back-and-forth
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micro FUSION
share internal structures for less allocation
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lock free operators
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lock free operators
and Work Stealing
cpu 1
cpu 2
cpu 3
cpu 4
cpu 5
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Reactor and
Spring
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Reactor and
Spring
and do I need Spring to use Reactor ?
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NO philosoraptor you don’t
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Reactor 3
is a dependency of
Spring 5
not the other way around
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5
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Java 8
baseline
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reactive
focus
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new WEB stack
WebFlux
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@RestController(“/user”)
public class UserController {
@GetMapping(“/{id}”)
Mono getUser(String id) {...}
}
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functional option
for Routing
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Spring Data
reactive repositories
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@GetMapping(“/{id}”)
Mono getUser(String id) {
return reactiveRepo.findOne(id);
}
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Reactor and the Network
reactor-netty
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reactor-netty
builds on Netty to provide
reactive I/O
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Client / Server
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TCP
or udp
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Http
and WebSockets
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HttpServer.create(0)
.newHandler((in, out) -> out
.sendWebsocket((i, o) ->
o.options(opt -> opt.flushOnEach())
.sendString(Flux.just("test")
.delayElementsMillis(100)
.repeat())
)
)
.block();
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still a bit low level
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still a bit low level
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reactor-kafka
topics as
Flux
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reactive API
over Kafka Producer / Consumer
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send(Flux)
into Kafka
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Flux receive()
from Kafka
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(currently in MILESTONE 1)
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Credits
● Springfield Plant: copyright FOX
● Raised Hand: CC0 (via Pixabay)
● Checklist: CC-By Crispy (via Flickr)
● Robot Devil: copyright FOX
● Volume Knob: CC0 (via Pixabay)
● Camel Shape: CC0 (via Pixabay)
● Dromedary Shape: CC-By-SA USPN,Whidou (via Wikimedia)
● Dam: CC-By-SA Matthew Hatton (via geograph.org.uk)
● Cogs: CC0 (via publicdomainpictures.net)
● Thread Balls: CC0 (via Pixabay)
● The Fortune Teller: Georges de la Tour (public domain)
● Microphone: CC0 (via Pexels)
● End Sands: CC0 (via Pixabay)
● logos: Pivotal, Spring, Twitter and Github logo copyright their
respective companies.