Don’t be Homer Simpson with your Reactor! - microXchg 2019

https://github.com/reactor/BlockHound/
https://github.com/reactor/reactor-tools/
https://spring.io/blog/2019/03/28/reactor-debugging-experience

Transcript

1. Don’t be Homer Simpson 
 with your Reactor! Sergei Egorov, Pivotal @bsideup https://simpsonswiki.com/wiki/File:Springfield_Nuclear_Power_Plant_6.png
2. Safe Harbor Statement The following is intended to outline the general direction of Pivotal's offerings. It is intended for information purposes only and may not be incorporated into any contract. Any information regarding pre-release of Pivotal offerings, future updates or other planned modifications is subject to ongoing evaluation by Pivotal and is subject to change. This information is provided without warranty or any kind, express or implied, and is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions regarding Pivotal's offerings. These purchasing decisions should only be based on features currently available. The development, release, and timing of any features or functionality described for Pivotal's offerings in this presentation remain at the sole discretion of Pivotal. Pivotal has no obligation to update forward looking information in this presentation.
3. About me • Staff Engineer at Pivotal’s Spring R&D, working on Project Reactor ⚛ • Testcontainers co-maintainer • Developer tools geek • … although spent most of my career building
 highly scalable backend services @bsideup
4. My first experience with
 reactive programming was like…
5. @bsideup
6. alright… alright…
7. @bsideup
8. Mono.fromRunnable()
9. Mono.fromRunnable() @bsideup
10. Mono.fromRunnable() My code @bsideup
11. Mono.fromRunnable() My code My code @bsideup
12. Mono.fromRunnable() My code My code My code Work! @bsideup
13. Mono.fromRunnable().subscribe() @bsideup
14. 1 week later…
15. I agree with Heinrich Apfelmus that the essence of functional reactive programming is to specify the dynamic behavior of a value completely at the time of declaration. “Reactive Sir” @bsideup
16. 1 week of production later…
17. @bsideup
18. What could go wrong
19. Whoa #1: exceptions
20. // com/example/demo/Example.java Flux.range(0, 5) .single() .subscribeOn(Schedulers.parallel()) .subscribe(); @bsideup
21. // com/example/demo/Example.java Flux.range(0, 5) .single() .subscribeOn(Schedulers.parallel()) .subscribe(); java.lang.IndexOutOfBoundsException: Source emitted more than one item at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(MonoSingle.java:129) at reactor.core.publisher.FluxRange$RangeSubscription.fastPath(FluxRange.java:129) at reactor.core.publisher.FluxRange$RangeSubscription.request(FluxRange.java:107) at reactor.core.publisher.MonoSingle$SingleSubscriber.request(MonoSingle.java:94) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.trySchedule(MonoSubscribeOn.java:186) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.onSubscribe(MonoSubscribeOn.java:131) at reactor.core.publisher.MonoSingle$SingleSubscriber.onSubscribe(MonoSingle.java:114) at reactor.core.publisher.FluxRange.subscribe(FluxRange.java:68) at reactor.core.publisher.MonoSingle.subscribe(MonoSingle.java:58) at reactor.core.publisher.Mono.subscribe(Mono.java:3711) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.run(MonoSubscribeOn.java:123) at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:84) at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:37) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) @bsideup
22. // com/example/demo/Example.java Flux.range(0, 5) .single() .subscribeOn(Schedulers.parallel()) .subscribe(); java.lang.IndexOutOfBoundsException: Source emitted more than one item at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(MonoSingle.java:129) at reactor.core.publisher.FluxRange$RangeSubscription.fastPath(FluxRange.java:129) at reactor.core.publisher.FluxRange$RangeSubscription.request(FluxRange.java:107) at reactor.core.publisher.MonoSingle$SingleSubscriber.request(MonoSingle.java:94) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.trySchedule(MonoSubscribeOn.java:186) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.onSubscribe(MonoSubscribeOn.java:131) at reactor.core.publisher.MonoSingle$SingleSubscriber.onSubscribe(MonoSingle.java:114) at reactor.core.publisher.FluxRange.subscribe(FluxRange.java:68) at reactor.core.publisher.MonoSingle.subscribe(MonoSingle.java:58) at reactor.core.publisher.Mono.subscribe(Mono.java:3711) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.run(MonoSubscribeOn.java:123) at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:84) at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:37) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) @bsideup
23. // com/example/demo/Example.java Flux.range(0, 5) .single() .subscribeOn(Schedulers.parallel()) .subscribe(); java.lang.IndexOutOfBoundsException: Source emitted more than one item at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(MonoSingle.java:129) at reactor.core.publisher.FluxRange$RangeSubscription.fastPath(FluxRange.java:129) at reactor.core.publisher.FluxRange$RangeSubscription.request(FluxRange.java:107) at reactor.core.publisher.MonoSingle$SingleSubscriber.request(MonoSingle.java:94) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.trySchedule(MonoSubscribeOn.java:186) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.onSubscribe(MonoSubscribeOn.java:131) at reactor.core.publisher.MonoSingle$SingleSubscriber.onSubscribe(MonoSingle.java:114) at reactor.core.publisher.FluxRange.subscribe(FluxRange.java:68) at reactor.core.publisher.MonoSingle.subscribe(MonoSingle.java:58) at reactor.core.publisher.Mono.subscribe(Mono.java:3711) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.run(MonoSubscribeOn.java:123) at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:84) at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:37) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Which source? @bsideup
24. // com/example/demo/Example.java Flux.range(0, 5) .single() .subscribeOn(Schedulers.parallel()) .subscribe(); java.lang.IndexOutOfBoundsException: Source emitted more than one item at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(MonoSingle.java:129) at reactor.core.publisher.FluxRange$RangeSubscription.fastPath(FluxRange.java:129) at reactor.core.publisher.FluxRange$RangeSubscription.request(FluxRange.java:107) at reactor.core.publisher.MonoSingle$SingleSubscriber.request(MonoSingle.java:94) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.trySchedule(MonoSubscribeOn.java:186) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.onSubscribe(MonoSubscribeOn.java:131) at reactor.core.publisher.MonoSingle$SingleSubscriber.onSubscribe(MonoSingle.java:114) at reactor.core.publisher.FluxRange.subscribe(FluxRange.java:68) at reactor.core.publisher.MonoSingle.subscribe(MonoSingle.java:58) at reactor.core.publisher.Mono.subscribe(Mono.java:3711) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.run(MonoSubscribeOn.java:123) at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:84) at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:37) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Which source? Where is “com.example.demo” package? @bsideup
25. // com/example/demo/Example.java Flux.range(0, 5) .single() .subscribeOn(Schedulers.parallel()) .subscribe(); java.lang.IndexOutOfBoundsException: Source emitted more than one item at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(MonoSingle.java:129) at reactor.core.publisher.FluxRange$RangeSubscription.fastPath(FluxRange.java:129) at reactor.core.publisher.FluxRange$RangeSubscription.request(FluxRange.java:107) at reactor.core.publisher.MonoSingle$SingleSubscriber.request(MonoSingle.java:94) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.trySchedule(MonoSubscribeOn.java:186) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.onSubscribe(MonoSubscribeOn.java:131) at reactor.core.publisher.MonoSingle$SingleSubscriber.onSubscribe(MonoSingle.java:114) at reactor.core.publisher.FluxRange.subscribe(FluxRange.java:68) at reactor.core.publisher.MonoSingle.subscribe(MonoSingle.java:58) at reactor.core.publisher.Mono.subscribe(Mono.java:3711) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber.run(MonoSubscribeOn.java:123) at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:84) at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:37) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Which source? Where is “com.example.demo” package? Does anyone rent an apartment in Prenzlauer Berg? @bsideup
26. Assembly vs Subscription
27. Flux.range(0, 5) Assembly @bsideup
28. Flux.range(0, 5) .filter(it -> it > 3) Assembly @bsideup
29. Flux.range(0, 5) .filter(it -> it > 3) .map(it -> it.toString()) Assembly @bsideup
30. Flux.range(0, 5) .filter(it -> it > 3) .map(it -> it.toString()) .single() Assembly @bsideup
31. Flux.range(0, 5) .filter(it -> it > 3) .map(it -> it.toString()) .single() .subscribeOn(Schedulers.parallel()) Assembly @bsideup
32. Flux.range(0, 5) .filter(it -> it > 3) .map(it -> it.toString()) .single() .subscribeOn(Schedulers.parallel()) .subscribe() Assembly @bsideup
33. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 @bsideup
34. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 * = subscriber @bsideup
35. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 @bsideup
36. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 @bsideup
37. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 @bsideup
38. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 @bsideup
39. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 .onSubscribe( ) * = subscription @bsideup
40. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 @bsideup
41. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 @bsideup
42. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 @bsideup
43. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 @bsideup
44. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 .request(max) @bsideup
45. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 .request(max) @bsideup
46. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 .request(max) @bsideup
47. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 .request(max) @bsideup
48. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 .request(max) @bsideup
49. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Subscription current thread parallel-1 .request(max) @bsideup
50. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Execution current thread parallel-1 .onNext(0) @bsideup
51. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Execution current thread parallel-1 .onNext(0) @bsideup
52. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Execution current thread parallel-1 .onNext(0) @bsideup
53. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Execution current thread parallel-1 .onNext(0) @bsideup
54. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Execution current thread parallel-1 .onNext(0) @bsideup
55. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Execution current thread parallel-1 .onNext(1) @bsideup
56. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Execution current thread parallel-1 .onNext(1) @bsideup
57. FluxRange FluxFilter FluxMap MonoSingle MonoSubscribeOn Execution current thread parallel-1 .onNext(1) java.lang.IndexOutOfBoundsException: Source emitted more than one item at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(Mono at reactor.core.publisher.FluxRange$RangeSubscription.fastPath(Flux at reactor.core.publisher.FluxRange$RangeSubscription.request(FluxR at reactor.core.publisher.MonoSingle$SingleSubscriber.request(Mono at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber. at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber. at reactor.core.publisher.MonoSingle$SingleSubscriber.onSubscribe(M at reactor.core.publisher.FluxRange.subscribe(FluxRange.java:68) at reactor.core.publisher.MonoSingle.subscribe(MonoSingle.java:58) at reactor.core.publisher.Mono.subscribe(Mono.java:3711) at reactor.core.publisher.MonoSubscribeOn$SubscribeOnSubscriber. @bsideup
58. Demo http://eskipaper.com/homer-jay-simpson-cartoon.html
59. Demo outcomes • Use .checkpoint(“something”) to “mark” reactive “milestones” • Read about Hooks.onOperatorDebug()… • … but use reactor-tools’ ReactorDebugAgent (works in prod too) • https://spring.io/blog/2019/03/06/flight-of-the-flux-1-assembly-vs- subscription - great article from Simon Basle about the internals @bsideup
60. Whoa #2: Blocking calls! https://blog.tfd.co.uk/2010/10/15/jackrabbit-performance/ @bsideup
61. How Reactor works @bsideup
62. Default thread pools Schedulers.parallel() - N threads, where N matches the CPUs count. Schedulers.single() - 1 thread handling all submitted tasks Schedulers.elastic() - dynamic, thread caching pool @bsideup
63. Mono.delay(ofSeconds(1)) @bsideup
64. Mono.delay(ofSeconds(1)) Mono.delay(ofSeconds(1), Schedulers.parallel()) @bsideup
65. Mono.delay(ofSeconds(1)) Mono.delay(ofSeconds(1), Schedulers.parallel()) Every non-instant operation 
 runs on the parallel scheduler
 by default! @bsideup
66. parallel-1 parallel-2 parallel-3 parallel-4 Non-blocking execution @bsideup
67. parallel-1 parallel-2 parallel-3 parallel-4 Non-blocking execution @bsideup
68. parallel-1 parallel-2 parallel-3 parallel-4 Non-blocking execution @bsideup
69. parallel-1 parallel-2 parallel-3 parallel-4 Non-blocking execution @bsideup
70. parallel-1 parallel-2 parallel-3 parallel-4 Non-blocking execution @bsideup
71. parallel-1 parallel-2 parallel-3 parallel-4 Blocking execution @bsideup
72. parallel-1 parallel-2 parallel-3 parallel-4 Blocking execution @bsideup
73. parallel-1 parallel-2 parallel-3 parallel-4 Blocking execution @bsideup
74. parallel-1 parallel-2 parallel-3 parallel-4 Blocking execution @bsideup
75. parallel-1 parallel-2 parallel-3 parallel-4 Blocking execution @bsideup
76. parallel-1 parallel-2 parallel-3 parallel-4 Blocking execution @bsideup
77. parallel-1 parallel-2 parallel-3 parallel-4 Blocking execution @bsideup
78. parallel-1 parallel-2 parallel-3 parallel-4 Blocking execution @bsideup
79. parallel-1 parallel-2 parallel-3 parallel-4 Blocking execution @bsideup
80. parallel-1 parallel-2 parallel-3 parallel-4 Blocking execution ⚠ no more tasks scheduled 
 until this task returns @bsideup
81. How to fix?
82. Use non-blocking APIs, or…
83. parallel-1 parallel-2 parallel-3 parallel-4 Custom thread pool! custom-1 custom-2 @bsideup
84. parallel-1 parallel-2 parallel-3 parallel-4 Custom thread pool! custom-1 custom-2 @bsideup
85. parallel-1 parallel-2 parallel-3 parallel-4 Custom thread pool! custom-1 custom-2 @bsideup
86. parallel-1 parallel-2 parallel-3 parallel-4 Custom thread pool! custom-1 custom-2 @bsideup
87. parallel-1 parallel-2 parallel-3 parallel-4 Custom thread pool! custom-1 custom-2 @bsideup
88. parallel-1 parallel-2 parallel-3 parallel-4 Custom thread pool! custom-1 custom-2 @bsideup
89. parallel-1 parallel-2 parallel-3 parallel-4 Custom thread pool! custom-1 custom-2 @bsideup
90. parallel-1 parallel-2 parallel-3 parallel-4 Custom thread pool! custom-1 custom-2 @bsideup
91. parallel-1 parallel-2 parallel-3 parallel-4 Custom thread pool! custom-1 custom-2 @bsideup
92. Demo http://eskipaper.com/homer-jay-simpson-cartoon.html
93. Demo outcomes • Blocking calls are bad, m’kay? • They may sneak into your production system • Use https://github.com/reactor/BlockHound to detect them • Use a dedicated pool for the necessary blocking calls, or schedule them on the Schedulers.elastic() built-in pool if they happen rarely @bsideup
94. “I use async APIs and I am safe!”
95. Yeah… sure.
96. Or…
97. Are you sure?
98. KafkaProducer#send(ProducerRecord,Callback) @bsideup
99. KafkaProducer#send(ProducerRecord,Callback) “Asynchronously send a record to a topic and invoke the provided callback when the send has been acknowledged.” - Javadoc @bsideup
100. KafkaProducer#send(ProducerRecord,Callback) “Asynchronously send a record to a topic and invoke the provided callback when the send has been acknowledged.” - Javadoc java.lang.Error: Blocking call! java.lang.Object#wait at reactor.BlockHound$Builder.lambda$new$0(BlockHound.java:154) at reactor.BlockHound$Builder.lambda$install$8(BlockHound.java:254) at reactor.BlockHoundRuntime.checkBlocking(BlockHoundRuntime.java:43) at java.lang.Object.wait(Object.java) at org.apache.kafka.clients.Metadata.awaitUpdate(Metadata.java:181) at org.apache.kafka.clients.producer.KafkaProducer.waitOnMetadata(KafkaProducer.java:938) at org.apache.kafka.clients.producer.KafkaProducer.doSend(KafkaProducer.java:823) at org.apache.kafka.clients.producer.KafkaProducer.send(KafkaProducer.java:803) @bsideup
101. KafkaProducer#send(ProducerRecord,Callback) “Asynchronously send a record to a topic and invoke the provided callback when the send has been acknowledged.” - Javadoc java.lang.Error: Blocking call! java.lang.Object#wait at reactor.BlockHound$Builder.lambda$new$0(BlockHound.java:154) at reactor.BlockHound$Builder.lambda$install$8(BlockHound.java:254) at reactor.BlockHoundRuntime.checkBlocking(BlockHoundRuntime.java:43) at java.lang.Object.wait(Object.java) at org.apache.kafka.clients.Metadata.awaitUpdate(Metadata.java:181) at org.apache.kafka.clients.producer.KafkaProducer.waitOnMetadata(KafkaProducer.java:938) at org.apache.kafka.clients.producer.KafkaProducer.doSend(KafkaProducer.java:823) at org.apache.kafka.clients.producer.KafkaProducer.send(KafkaProducer.java:803) @bsideup
102. KafkaProducer#send(ProducerRecord,Callback) “Asynchronously send a record to a topic and invoke the provided callback when the send has been acknowledged.” - Javadoc java.lang.Error: Blocking call! java.lang.Object#wait at reactor.BlockHound$Builder.lambda$new$0(BlockHound.java:154) at reactor.BlockHound$Builder.lambda$install$8(BlockHound.java:254) at reactor.BlockHoundRuntime.checkBlocking(BlockHoundRuntime.java:43) at java.lang.Object.wait(Object.java) at org.apache.kafka.clients.Metadata.awaitUpdate(Metadata.java:181) at org.apache.kafka.clients.producer.KafkaProducer.waitOnMetadata(KafkaProducer.java:938) at org.apache.kafka.clients.producer.KafkaProducer.doSend(KafkaProducer.java:823) at org.apache.kafka.clients.producer.KafkaProducer.send(KafkaProducer.java:803) https://issues.apache.org/jira/browse/KAFKA-3539 @bsideup
103. long remainingWaitMs = maxWaitMs; long elapsed; // Issue metadata requests until we have metadata for the topic or maxWaitTimeMs is exceeded. // In case we already have cached metadata for the topic, but the requested partition is greater // than expected, issue an update request only once. This is necessary in case the metadata // is stale and the number of partitions for this topic has increased in the meantime. do { log.trace("Requesting metadata update for topic {}.", topic); metadata.add(topic); int version = metadata.requestUpdate(); sender.wakeup(); try { metadata.awaitUpdate(version, remainingWaitMs); } catch (TimeoutException ex) { // Rethrow with original maxWaitMs to prevent logging exception with remainingWaitMs throw new TimeoutException("Failed to update metadata after " + maxWaitMs + " ms."); } cluster = metadata.fetch(); elapsed = time.milliseconds() - begin; if (elapsed >= maxWaitMs) throw new TimeoutException("Failed to update metadata after " + maxWaitMs + " ms."); if (cluster.unauthorizedTopics().contains(topic)) throw new TopicAuthorizationException(topic); remainingWaitMs = maxWaitMs - elapsed; partitionsCount = cluster.partitionCountForTopic(topic); } while (partitionsCount == null); waitOnMetadata(record.topic(), record.partition(), maxBlockTimeMs); Default is “60 seconds” @bsideup
104. @bsideup
105. Tips & tricks http://eskipaper.com/homer-jay-simpson-cartoon.html @bsideup
106. Your Reactor should be like:
107. https://9gag.com/gag/aqKWPwY
108. Takeaways • https://github.com/reactor/reactor-tools • Flux#checkpoint() / Flux#log() • https://github.com/reactor/BlockHound • Async APIs - trust, but verify @bsideup
109. @bsideup bsideup