Spring I/O 2018 でお話があった以下のセッションについて自分なりにまとめてみました。
- Flight of the Flux
https://speakerdeck.com/simonbasle/flight-of-the-flux
- Under the hood of Reactive Data Access
https://speakerdeck.com/mp911de/under-the-hood-of-reactive-data-access-1
- REST beyond the obvious
https://speakerdeck.com/olivergierke/rest-beyond-the-obvious-api-design-for-ever-evolving-systems
11. Flight of the Flux: A look at Reactor execution model
Nothing happens until you subscribe
Assembly & Execution Time
Debug
Hot&Cold Publisher(例例外)
Concurrency Agnosticだけどスレッドを使う
publishOn&subscribeOn
work stealing
その他のよしなに系処理理
macro & micro fusion
!11
26. Assembly Time / Execution Time はタイミングが違う
java.lang.IndexOutOfBoundsException: Source emitted more than one item
at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(MonoSingle.java:129)
at reactor.core.publisher.FluxFlatMap$FlatMapMain.tryEmitScalar(FluxFlatMap.java:445)
at reactor.core.publisher.FluxFlatMap$FlatMapMain.onNext(FluxFlatMap.java:379)
at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:121)
at reactor.core.publisher.FluxRange$RangeSubscription.slowPath(FluxRange.java:154)
at reactor.core.publisher.FluxRange$RangeSubscription.request(FluxRange.java:109)
at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:162)
at reactor.core.publisher.FluxFlatMap$FlatMapMain.onSubscribe(FluxFlatMap.java:332)
at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:
90)
at reactor.core.publisher.FluxRange.subscribe(FluxRange.java:68)
at reactor.core.publisher.FluxMapFuseable.subscribe(FluxMapFuseable.java:63)
at reactor.core.publisher.FluxFlatMap.subscribe(FluxFlatMap.java:97)
at reactor.core.publisher.MonoSingle.subscribe(MonoSingle.java:58)
at reactor.core.publisher.Mono.subscribe(Mono.java:3096)
at reactor.core.publisher.Mono.subscribeWith(Mono.java:3204)
at reactor.core.publisher.Mono.subscribe(Mono.java:3090)
at reactor.core.publisher.Mono.subscribe(Mono.java:3057)
at reactor.core.publisher.Mono.subscribe(Mono.java:3029)
at reactor.guide.GuideTests.debuggingCommonStacktrace(GuideTests.java:995)
→ stacktraceが追いづらい
!26
27. Hooks.onOperatorDebug();
Assembly timeの機構を利利⽤用
アプリ起動時(Flux,Monoのインスタンス
化前)に⾏行行われる
java.lang.IndexOutOfBoundsException: Source emitted more than one item
at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(MonoSingle.java:120)
at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:314)
...
...
at reactor.core.publisher.Mono.subscribeWith(Mono.java:2668)
at reactor.core.publisher.Mono.subscribe(Mono.java:2629)
at reactor.core.publisher.Mono.subscribe(Mono.java:2604)
at reactor.core.publisher.Mono.subscribe(Mono.java:2582)
at reactor.guide.GuideTests.debuggingActivated(GuideTests.java:727)
Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException:
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)
org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:55)
org.junit.rules.RunRules.evaluate(RunRules.java:20)
Error has been observed by the following operator(s):
|_ Flux.single(TestWatcher.java:55)
Debugモードにする魔法
エラーが起きるとFluxがnewされた箇所を
Assembly Timeに解析した内容を元に
追記してくれる
(がコストが⾼高い)!27
28. checkpoint()
Debugの仕⽅方2
!28
public void checkpointWithDescriptionIsLight() {
StringWriter sw = new StringWriter();
Flux<Integer> tested = Flux.range(1, 10)
.map(i -> i < 3 ? i : null)
.filter(i -> i % 2 == 0)
.checkpoint("foo")
.doOnError(t -> t.printStackTrace(new PrintWriter(sw)));
StepVerifier.create(tested)
.expectNext(2)
.verifyError();
String debugStack = sw.toString();
}
Assembly site of producer [reactor.core.publisher.FluxFilterFuseable] is
identified by light checkpoint [foo].
29. Nothing happens until you subscribe… ですが 例例外あり
Hot Publisher
Cold Publisher
これはこっちの話
subscriptionごとにデータを新しくこさえる
例例:HTTP request
⼀一度でもsubscribeされたら(⼀一度データが流れ出したら)
その後はお構いなく流れていく
途中からsubscribeしたSubscriberはsubscribeするより前に
何かが起こっていることになる
例例:Processorクラスを継承したもの
!29
31. Flux<String> source = Flux.fromIterable(Arrays.asList("blue", "green", "orange", "purple"))
.map(String::toUpperCase);
source.subscribe(d -> System.out.println("Subscriber 1 to Cold Source: "+d));
source.subscribe(d -> System.out.println("Subscriber 2 to Cold Source: "+d));
Subscriber 1 to Cold Source: BLUE
Subscriber 1 to Cold Source: GREEN
Subscriber 1 to Cold Source: ORANGE
Subscriber 1 to Cold Source: PURPLE
Subscriber 2 to Cold Source: BLUE
Subscriber 2 to Cold Source: GREEN
Subscriber 2 to Cold Source: ORANGE
Subscriber 2 to Cold Source: PURPLE
Cold Publisher
!31
32. UnicastProcessor<String> hotSource = UnicastProcessor.create();
Flux<String> hotFlux = hotSource.publish()
.autoConnect()
.map(String::toUpperCase);
hotSource.onNext("blue");
hotSource.onNext("green");
hotFlux.subscribe(d -> System.out.println("Subscriber 1 to Hot Source: "+d));
hotFlux.subscribe(d -> System.out.println("Subscriber 2 to Hot Source: "+d));
hotSource.onNext("orange");
hotFlux.subscribe(d -> System.out.println("Subscriber 3 to Hot Source: "+d));
hotSource.onNext("purple");
hotSource.onComplete();
Hot Publisher
!32
33. Subscriber 1 to Hot Source: BLUE
Subscriber 1 to Hot Source: GREEN
Subscriber 1 to Hot Source: ORANGE
Subscriber 2 to Hot Source: ORANGE
Subscriber 1 to Hot Source: PURPLE
Subscriber 2 to Hot Source: PURPLE
Subscriber 3 to Hot Source: PURPLE
Hot Publisher
UnicastProcessor<String> hotSource = UnicastProcessor.create();
Flux<String> hotFlux = hotSource.publish()
.autoConnect()
.map(String::toUpperCase);
hotSource.onNext("blue");
hotSource.onNext("green");
hotFlux.subscribe(d -> System.out.println("Subscriber 1 to Hot Source: "+d));
hotFlux.subscribe(d -> System.out.println("Subscriber 2 to Hot Source: "+d));
hotSource.onNext("orange");
hotFlux.subscribe(d -> System.out.println("Subscriber 3 to Hot Source: "+d));
hotSource.onNext("purple");
hotSource.onComplete();
!33
45. Spring Data で Reactive に DB アクセスできるもの
•Spring Data Commons
•Spring Data JPA
•Spring Data KeyValue
•Spring Data LDAP
•Spring Data MongoDB
•Spring Data REST
•Spring Data Redis
•Spring Data for Apache Cassandra
•Spring Data for Apache Geode
•Spring Data for Apache Solr
•Spring Data for Pivotal GemFire
•Spring Data Couchbase (community module)
•Spring Data Elasticsearch (community module)
•Spring Data Neo4j (community module)
http://projects.spring.io/spring-data/
ドキュメント指向
Key-Value型
Column型
KVS
!45
アクションログ
46. Spring Data
JDBC
JVM
RDBS
Reactor
MongoDB
Reactive Streams
Java Driver
JVM
MongoDB
Reactor
Lettuce
JVM
Redis
Reactor
DataStax Java driver
for Cassandra
JVM
Cassandra
Reactor
Reactive
Couchbase
JVM
Couchbase
Server
Spring Data JPA
Spring Data
MongoDB
Spring Data
Redis
Spring Data for
Cassandra
Spring Data
Couchbase
Under the hood of ~の話のスコープ
… 各ベンダが⽤用意している DB Driver の Reactive 対応状況
!46
47. Spring Data
JDBC
JVM
RDBS
Reactor
MongoDB
Reactive Streams
Java Driver
JVM
MongoDB
Reactor
Lettuce
JVM
Redis
Reactor
DataStax Java driver
for Cassandra
JVM
Cassandra
Reactor
Reactive
Couchbase
JVM
Couchbase
Server
Spring Data JPA
Spring Data
MongoDB
Spring Data
Redis
Spring Data for
Cassandra
Spring Data
Couchbase
Under the hood of ~の話のスコープ
… 各ベンダが⽤用意している DB Driver の Reactive 対応状況
Fully blocking API
ADBA,R2DBCなどがnon-blocking api
!47