What's new in Reactor Californium, the 3rd release train (3.2.x) of Project Reactor.

1. Reactor Californium
Stephane Maldini - @smaldini

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But Really ?
Californium ?

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Just Released
5

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Reactor Core 3.2
Reactor Addons 3.2
Reactor Netty 0.8
6

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Used by
Spring Framework
5.1

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Used by
Spring Framework
5.1
8
(And Soon®
Spring Boot 2.1)

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Reactor Core 3.2

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Initial Micrometer Support
10
Monitor Flux and Mono

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Initial Micrometer Support
11
New metric() operator
with auto detection for name() and tag()

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Initial Micrometer Support
12
Noop if Micrometer not on class path

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Initial Micrometer Support
13
Flux.range(1, 1000)
.delayUntil(i -> Mono.delay(Duration.ofMillis(100*(i % 10))))
.name("test-flow")
.log()
.metrics()
.limitRate(10)
.repeat()
.blockLast();

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Initial Micrometer Support
14
Flux.range(1, 1000)
.delayUntil(i -> Mono.delay(Duration.ofMillis(100*(i % 10))))
.name("test-flow")
.log()
.metrics()
.limitRate(10)
.repeat()
.blockLast();
Identify the flux for meaningful metrics

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Initial Micrometer Support : Good to know
15
Time delays between start and data signals…
…Then between each data signals
Time full flow duration if finite
Tag by signal type
Detect Malformed Reactive Signals

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Initial Micrometer Support w/ Spring Boot
16
compile "io.projectreactor:reactor-core:3.2.0.RELEASE"
compile "org.springframework.boot:spring-boot-starter-webflux"
compile "org.springframework.boot:spring-boot-starter-actuator"
compile "io.micrometer:micrometer-registry-prometheus"

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Initial Micrometer Support w/ Spring Boot
17
compile "io.projectreactor:reactor-core:3.2.0.RELEASE"
compile "org.springframework.boot:spring-boot-starter-webflux"
compile "org.springframework.boot:spring-boot-starter-actuator"
compile "io.micrometer:micrometer-registry-prometheus"

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reactor.util.context.Context: reactive flow attributes
19
Reward end-to-end users with unique features in 3.2

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reactor.util.context.Context: reactive flow attributes
20
Immutable container using optimized copy-on-write

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reactor.util.context.Context: reactive flow attributes
21
Propagate at subscribe time
from the subscribing side to the producing side.

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reactor.util.context.Context: reactive flow attributes
22
StepVerifier.create(
Mono.subscriberContext()
.subscriberContext(Context.of("initial", "value"))
)
.expectNextMatches(c -> c.hasKey("initial"))
.verifyComplete();

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reactor.util.context.Context: reactive flow attributes
23
StepVerifier.create(
Mono.subscriberContext()
.subscriberContext(Context.of("initial", "value"))
)
.expectNextMatches(c -> c.hasKey("initial"))
.verifyComplete();
Read from the current subscription Write during current subscription

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reactor.util.context.Context: reactive flow attributes
24
StepVerifier.create(
Flux.just("foo")
.flatMap(v -> Mono.subscriberContext())
.subscriberContext(Context.of("initial", "value"))
)
.expectNextMatches(c -> c.hasKey("initial"))
.verifyComplete();

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reactor.util.context.Context: reactive flow attributes
25
StepVerifier.create(
Flux.just("foo")
.flatMap(v -> Mono.subscriberContext())
.subscriberContext(Context.of("initial", "value"))
)
.expectNextMatches(c -> c.hasKey("initial"))
.verifyComplete();
Works inside nested flows

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Context: an alternative to Thread-Local
26
Spring Security
Spring Cloud Sleuth
doOnDiscard
onErrorContinue
Spring Data
…

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DoOnDiscard
27
Reroute upstream operators discarded items

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DoOnDiscard
28
Useful to build strongly consistent reactive flows
Even more useful to release resources
such as pooled buffers (hello netty!)

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DoOnDiscard : react to filtered items
29
AtomicInteger discardNumberCount = new AtomicInteger();
Flux.range(1, 12)
.filter(i -> i % 2 == 0)
.doOnDiscard(Number.class, i -> discardNumberCount.incrementAndGet())
.subscribe();
Assertions.assertThat(discardNumberCount).hasValue(6);

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DoOnDiscard : react to partial collections
30
DirectProcessor<String> p = DirectProcessor.create();
Disposable d = p.collectList()
.doOnDiscard(String.class, System.out::println)
.subscribe();
p.onNext("a");
p.onNext("b");
p.onNext("c");
d.dispose();

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DoOnDiscard : react to cancelled items
31
DirectProcessor<String> p = DirectProcessor.create();
Disposable d = p.collectList()
.doOnDiscard(String.class, System.out::println)
.subscribe();
p.onNext("a");
p.onNext("b");
p.onNext("c");
d.dispose(); a
b
c
Console Output

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DoOnDiscard : testable behavior
32
StepVerifier.create(Flux.range(1, 12)
.filter(i -> i % 2 == 0)
)
.expectNext(2, 4, 6, 8, 10, 12)
.expectComplete()
.verifyThenAssertThat()
.hasDiscarded(1, 3, 5, 7, 9, 11);

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DoOnDiscard : scope of work
33
Limited number of supported operators
Planning to add more during 3.2.x

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DoOnDiscard : scope of work
34
Limited number of supported operators
Planning to add more during 3.2.x
Look for this in JavaDoc

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DoOnDiscard : scope of work
35
Does not guarantee exactly-once callback invocation
combineLatest
overlapping buffers
overlapping windows

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DoOnDiscard : scope of work
36
Use your own de-duplication if you need exactly-once
semantics

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onErrorContinue
37
Reroute upstream operators selected errors

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onErrorContinue
38
Useful to build more resilient reactive flows
Even more useful to messaging use cases
such as data processing pipelines

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onErrorContinue : keep things running
39
Flux.just(0, 1)
.map(i -> 1 / i)
.onErrorContinue((e, data) -> System.out.println(e.getMessage() + " - " + data))
.log()
.subscribe();

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onErrorContinue : keep things running
40
Flux.just(0, 1)
.map(i -> 1 / i)
.onErrorContinue((e, data) -> System.out.println(e.getMessage() + " - " + data))
.log()
.subscribe();
A Door left open for errors

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onErrorContinue : keep things running
41
Flux.just(0, 1)
.map(i -> 1 / i)
.onErrorContinue((e, data) -> System.out.println(e.getMessage() + " - " + data))
.log()
.subscribe();
Console Output
[main] INFO reactor.Flux.ContextStart.1 - | onSubscribe([Fuseable] FluxContextStart.ContextStartSubscriber)
[main] INFO reactor.Flux.ContextStart.1 - | request(unbounded)
/ by zero - 0
[main] INFO reactor.Flux.ContextStart.1 - | onNext(1)
[main] INFO reactor.Flux.ContextStart.1 - | onComplete()

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onErrorContinue : keep things running
42
Flux.just(0, 1)
.map(i -> 1 / i)
.onErrorContinue((e, data) -> System.out.println(e.getMessage() + " - " + data))
.log()
.subscribe();
Console Output
[main] INFO reactor.Flux.ContextStart.1 - | onSubscribe([Fuseable] FluxContextStart.ContextStartSubscriber)
[main] INFO reactor.Flux.ContextStart.1 - | request(unbounded)
/ by zero - 0
[main] INFO reactor.Flux.ContextStart.1 - | onNext(1)
[main] INFO reactor.Flux.ContextStart.1 - | onComplete()
/ by zero - 0

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onErrorContinue : keep things running
43
Flux.just(0, 1)
.map(i -> 1 / i)
.onErrorContinue((e, data) -> System.out.println(e.getMessage() + " - " + data))
.log()
.subscribe();
Console Output
[main] INFO reactor.Flux.ContextStart.1 - | onSubscribe([Fuseable] FluxContextStart.ContextStartSubscriber)
[main] INFO reactor.Flux.ContextStart.1 - | request(unbounded)
/ by zero - 0
[main] INFO reactor.Flux.ContextStart.1 - | onNext(1)
[main] INFO reactor.Flux.ContextStart.1 - | onComplete()
onNext(1)

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onErrorContinue : keep things running
44
Flux.just(0, 1)
.flatMap(f -> Mono.just(f).map(i -> 1/i))
.onErrorContinue((e, data) -> System.out.println(e.getMessage() + " - " + data))
.log()
.subscribe();

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onErrorContinue : keep things running
45
Flux.just(0, 1)
.flatMap(f -> Mono.just(f).map(i -> 1/i))
.onErrorContinue((e, data) -> System.out.println(e.getMessage() + " - " + data))
.log()
.subscribe();
Nested Flows support - Thanks Context !

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onErrorContinue : scope of work
46
Limited number of supported operators
Planning to add more during 3.2.x

47. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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onErrorContinue : scope of work
47
Limited number of supported operators
Planning to add more during 3.2.x

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onErrorContinue : scope of work
48
Error must not be related to
the start or the end of sequence

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onErrorContinue : scope of work
49
Impact the way the flow is working
As the operator usually needs to request an extra item

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onErrorContinue : scope of work
50
Impact the way the flow is working
As the operator usually needs to request an extra item
No use-case for Mono#onErrorContinue

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retryBackoff : pragmatic retry
51
The new retry operator you will want to use all the time

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retryBackoff : pragmatic retry
52
The new retry operator you will want to use all the time
With randomized exponential timeouts

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retryBackoff : pragmatic retry
53
The new retry operator you will want to use all the time
With randomized exponential timeouts
Promoted operator from Reactor Addons 👍

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retryBackoff : pragmatic retry
54
StepVerifier.withVirtualTime(() ->
Mono.error(new IOException("boom retry"))
.doOnError(e -> elapsedList.add(Schedulers.parallel().now(TimeUnit.MILLISECONDS)))
.retryBackoff(4, Duration.ofMillis(100), Duration.ofMillis(2000))
)
.thenAwait(Duration.ofMinutes(1))
.expectErrorSatisfies(e -> assertThat(e).hasMessage("Retries exhausted: 4/4"))
.verify();
System.out.println(elapsedList);

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retryBackoff : pragmatic retry
55
StepVerifier.withVirtualTime(() ->
Mono.error(new IOException("boom retry"))
.doOnError(e -> elapsedList.add(Schedulers.parallel().now(TimeUnit.MILLISECONDS)))
.retryBackoff(4, Duration.ofMillis(100), Duration.ofMillis(2000))
)
.thenAwait(Duration.ofMinutes(1))
.expectErrorSatisfies(e -> assertThat(e).hasMessage("Retries exhausted: 4/4"))
.verify();
System.out.println(elapsedList);
pro-tip: use virtual time to instant-test time driven sequences

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retryBackoff : pragmatic retry
56
StepVerifier.withVirtualTime(() ->
Mono.error(new IOException("boom retry"))
.doOnError(e -> elapsedList.add(Schedulers.parallel().now(TimeUnit.MILLISECONDS)))
.retryBackoff(4, Duration.ofMillis(100), Duration.ofMillis(2000))
)
.thenAwait(Duration.ofMinutes(1))
.expectErrorSatisfies(e -> assertThat(e).hasMessage("Retries exhausted: 4/4"))
.verify();
System.out.println(elapsedList); Console Output
[0, 129, 386, 749, 1463]

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usingWhen : Arbitrary resource lifecycle binding
57
Flux<String> flux = Flux.usingWhen(Mono.fromCallable(TestResource::new),
d -> Flux.just("Transaction started", "work in transaction", "more work in transaction"),
TestResource::commit,
TestResource::rollback);
StepVerifier.create(flux)
.expectNext("Transaction started")
.expectNext("work in transaction")
.expectNext("more work in transaction")
.verifyComplete();

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usingWhen : Arbitrary resource lifecycle binding
58
Flux<String> flux = Flux.usingWhen(Mono.fromCallable(TestResource::new),
d -> Flux.just("Transaction started", "work in transaction", "more work in transaction"),
TestResource::commit,
TestResource::rollback);
StepVerifier.create(flux)
.expectNext("Transaction started")
.expectNext("work in transaction")
.expectNext("more work in transaction")
.verifyComplete();
Commit method will be used

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usingWhen : Arbitrary resource lifecycle binding
59
Flux<String> flux = Flux.usingWhen(Mono.fromCallable(TestResource::new),
d -> Flux.just("Transaction started").concatWith(Mono.error(new Exception("fail"))),
TestResource::commit,
TestResource::rollback);
StepVerifier.create(flux)
.expectNext("Transaction started")
.verifyErrorMessage(“fail");
Rollback method will be used

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usingWhen : Arbitrary resource lifecycle binding
60
Flux<String> flux = Flux.usingWhen(Mono.fromCallable(TestResource::new),
d -> Flux.just("Transaction started").concatWith(Mono.error(new Exception("fail"))),
TestResource::commit,
TestResource::rollback,
TestResource::rollback);
StepVerifier.create(flux)
.expectNext("Transaction started”)
.thenCancel()
.verify();
Rollback method will be used on cancel too

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Learn about all improvements
61
https://github.com/reactor/reactor-core/releases/tag/v3.2.0.RELEASE

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Things that are still in the oven
62
Full Processor API refactoring

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Things that are still in the oven
63
Full Processor API refactoring
Too impacting for now

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Things that are still in the oven
64
Converting Marble Diagrams to SVG
Shout Out to @thekalinga
Metrics for Schedulers
new FluxSink#tryNext
Website improvements

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Learn more from Simon Baslé
3:20 Flight of the Flux: A Look at Reactor Execution Model

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Reactor Netty 0.8

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The API refining continues
67
Aligned HttpClient APIs with WebClient
Merged Options and Stateless builders
into XxxClient/XxxServer

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The API refining continues
68
HttpClient.create()
.wiretap()
.followRedirect(true)
.get()
.uri("https://projectreactor.io")
.responseContent()
.asString()
.limitRate(1)
.reduce(String::concat)
.block(Duration.ofSeconds(30));

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The API refining continues
69
HttpClient.create()
.wiretap()
.followRedirect(true)
.get()
.uri("https://projectreactor.io")
.responseContent()
.asString()
.limitRate(1)
.reduce(String::concat)
.block(Duration.ofSeconds(30));
Single level of nesting

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Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
The API refining continues
70
HttpClient.create()
.wiretap()
.followRedirect(true)
.get()
.uri("https://projectreactor.io")
.responseContent()
.asString()
.limitRate(1)
.reduce(String::concat)
.block(Duration.ofSeconds(30));
Specify client options in the builder

71. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
The API refining continues
71
HttpClient.create()
.wiretap()
.followRedirect(true)
.get()
.uri("https://projectreactor.io")
.responseContent()
.asString()
.limitRate(1)
.reduce(String::concat)
.block(Duration.ofSeconds(30));
Basic decoding OoB

72. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 72
Learn more from Violeta Georgieva
11:30 Reactor Netty, the Default Spring Boot 2.0 Runtime

73. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Next ?

74. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
What’s next ?
74
dysprosium [Dy] ?
Dubnium [Db] ?
Darmstadtium [Ds] ?

75. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Thanks