The Value of Reactive

The Value Of Reactive
Stephane Maldini - Reactive Engineering @ Pivotal
@smaldini

The Value Of Reactive
What is it ? Where is the value ?

3
No, I do not have a medium blog
=+
@smaldini

Reactive
Programming
● The next frontier for high-efficiency applications
● Non-blocking and allows for concurrent executions
● Often associated with functional programming
● Have no opinion on async and many flows are totally
synchronous
● Resilient with graceful error handling and interruptions
(producer or consumer related)
😴

A reactive API primer
6
@GetMapping("/health")
public Mono<Health> compositeHealth() {
return Mono.zip(
webClient.get()
.uri(“https://alpha-service/health")
.retrieve()
.bodyToMono(Health.class),
webClient.get()
.uri("https://bravo-service/health")
.retrieve()
.bodyToMono(Health.class),
(alpha, bravo) -> composite(alpha, bravo))
.switchIfEmpty(emptyComposite());
}

Is declarative style too disruptive
to scale across dev teams ?
7

Debugging Reactive flows
8
java.lang.RuntimeException: Am I looking like a nice stacktrace friends ?
at io.spring.workshop.tradingservice.TradingCompanyClient.lambda$getTradingCompany$0(TradingCompanyClient.java:38) ~[classes/:na]
at reactor.core.publisher.FluxPeekFuseable$PeekFuseableSubscriber.onNext(FluxPeekFuseable.java:190) ~[reactor-core-3.3.0]
at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1575) ~[reactor-core-3.3.0]
at reactor.core.publisher.MonoFlatMap$FlatMapInner.onNext(MonoFlatMap.java:241) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:349) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:121) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxContextStart$ContextStartSubscriber.onNext(FluxContextStart.java:103) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxMapFuseable$MapFuseableConditionalSubscriber.onNext(FluxMapFuseable.java:287) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxFilterFuseable$FilterFuseableConditionalSubscriber.onNext(FluxFilterFuseable.java:331) ~[reactor-core-3.3.0]
at reactor.core.publisher.MonoCollectList$MonoCollectListSubscriber.onComplete(MonoCollectList.java:121) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:136) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:252) ~[reactor-core-3.3.0]
at reactor.netty.channel.FluxReceive.terminateReceiver(FluxReceive.java:391) ~[reactor-netty-0.9.0]
at reactor.netty.channel.FluxReceive.drainReceiver(FluxReceive.java:197) ~[reactor-netty-0.9.0]
at reactor.netty.channel.FluxReceive.onInboundComplete(FluxReceive.java:338) ~[reactor-netty-0.9.0]
at reactor.netty.channel.ChannelOperations.onInboundComplete(ChannelOperations.java:350) ~[reactor-netty-0.9.0]
at reactor.netty.channel.ChannelOperations.terminate(ChannelOperations.java:399) ~[reactor-netty-0.9.0]
at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:555) ~[reactor-netty-0.9.0]
…

Debugging Reactive flows
9
java.lang.RuntimeException: Am I looking like a nice stacktrace friends ?
at io.spring.workshop.tradingservice.TradingCompanyClient.lambda$getTradingCompany$0(TradingCompanyClient.java:38) ~[classes/:na]
at reactor.core.publisher.FluxPeekFuseable$PeekFuseableSubscriber.onNext(FluxPeekFuseable.java:190) ~[reactor-core-3.3.0]
at reactor.core.publisher.MonoFlatMap$FlatMapInner.onNext(MonoFlatMap.java:241) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:349) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:121) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxContextStart$ContextStartSubscriber.onNext(FluxContextStart.java:103) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxMapFuseable$MapFuseableConditionalSubscriber.onNext(FluxMapFuseable.java:287) ~[reactor-core-3.3.0]
at reactor.core.publisher.FluxFilterFuseable$FilterFuseableConditionalSubscriber.onNext(FluxFilterFuseable.java:331) ~[reactor-core-3.3.0]
at reactor.core.publisher.MonoCollectList$MonoCollectListSubscriber.onComplete(MonoCollectList.java:121) ~[reactor-core-3.3.0]
at reactor.netty.channel.FluxReceive.terminateReceiver(FluxReceive.java:391) ~[reactor-netty-0.9.0]
at reactor.netty.channel.FluxReceive.drainReceiver(FluxReceive.java:197) ~[reactor-netty-0.9.0]
at reactor.netty.channel.FluxReceive.onInboundComplete(FluxReceive.java:338) ~[reactor-netty-0.9.0]
at reactor.netty.channel.ChannelOperations.onInboundComplete(ChannelOperations.java:350) ~[reactor-netty-0.9.0]
at reactor.netty.channel.ChannelOperations.terminate(ChannelOperations.java:399) ~[reactor-netty-0.9.0]
at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:555) ~[reactor-netty-0.9.0]
…
You ?

Using blocking code in reactive callbacks
10
TradingCompany tradingCompany = this.restTemplate.exchange(
get("http://localhost:8082/details/{ticker}", ticker),
TradingCompany.class)
.getBody();

Using blocking code in reactive callbacks
11
someMono.doOnSuccess(data -> {
.getBody();
return tradingCompany;
});
💩

What are you priorities ?
13
Time To Market / Dev Productivity

14
Day 2 Operations / Observability

15
[…]

16
Running costs / efficiency
[…]

17
Reactive ?Running costs / efficiency
[…]

Give me
18
Reasons
To use this stuff

19
Order(s) of Magnitude  
more efficient
🤑

• Lower Number of processes/threads used by instance
• Lower Memory Pressure and associated costs (Garbage collectors)
• Lower Hardware specification requirements
• Lower Startup time
20
more efficient

Show me some numbers
21
more efficient

22
more efficient
Spring WebFlux.Fn - Reactor Netty - 4 threads
&
Spring MVC - Tomcat - 200 threads
With a simple hello world String rendering
128 / steps up to 4000 20s 20min

23
more efficient

24
more efficient MVCWebFlux

25
more efficient
😎
🤒

26
more efficient
Moar Old Gen
Moar Young Gen

27
more efficient

28
more efficient
x2

29
more efficient
😎 ⏰

30
Designed for  
connection volume scalability
📱Order(s) of Magnitude  
more efficient

• Lower Number of instances running a same application
• Lower Impact from traffic latency diversity
• Lower Impact from persistent http traffic (websocket, sse, http2…)
31
Designed for  

32
Spring WebFlux.Fn - Reactor Netty - 4 threads
&
Spring MVC - Tomcat - 200 threads
With a 100ms delayed hello world String rendering
128 / steps up to 4000 20s 20min
Designed for  

Designed for  
33
MVC (async)WebFlux

Designed for  
34🤢

35
Designed for  

36
x4
Designed for  

37
⏰⏰
Designed for  

How does the response delay impact each model ?
38
Designed for  

39
Designed for  
WebFlux WebFlux (with response delay)

40
Designed for  

41
Designed for  
No major impact from backend delays

42
Designed for  
WebMVC (with response delay)WebMVC

43
Designed for  
WebMVC (with response delay)WebMVC
Rapidly degrading running conditions

44
Designed for  
WebMVC WebMVC (with response delay)

45
Designed for  
WebMVC WebMVC (with response delay)
x4 slower due to backend delays

46
Designed for  
📱Order(s) of Magnitude  
more efficient

47
Sleep Well, 
get less paged
📟
more efficient Designed for  

Sleep Well, 
get less paged
• Greater resilience to runtime errors, including memory issues
• Greater availability at any point in time, specially under stress
• Easier resources use modeling
48

Sleep Well, 
get less paged
49
Figure 1.a:  
A blocking JVM HTTP server with no flow control

Sleep Well, 
get less paged
Reactive IO allows reading when application capacity permits
50

Sleep Well, 
get less paged
Reactive IO only writes back application data when client capacity permits
51

52
Sleep Well, 
get less paged

53
Very similar resources use profile
Sleep Well, 
get less paged

Sleep Well, 
get less paged
54
Can reactive programming help with JVM OutOfMemory
exceptions caused by incoming request traffic ?

Sleep Well, 
get less paged
• Yes, using a reactive IO runtime, request body overflow is isolated
• A Connection Read causing an OutOfMemory will be rejected
55

Sleep Well, 
get less paged
• Yes, using a reactive IO runtime, request body overflow is isolated
• A Connection Read causing an OutOfMemory will be rejected
• With a blocking IO runtime, request body overflow will be fatal
• The entire application will crash or be in unrecoverable state
56

57
Sleep Well, 
get less paged
more efficient
Designed for  

58
Sleep Well, 
get less paged
more efficient
Designed for  
Event-Driven
Less Threads - Memory
Start quicker
Improve Latency*
Unlocks hyper concurrency
Connected Experience
Slow/Fast traffic
Near-Always Available
Flow Control
Predictable load
Resilient

59
What do you do with these
qualities ?
🤓

60
Write Any Microservice
Resilient
Smaller resources footprint
Remote calls parallelization
Hedge Clients

61
Write Any Microservice
Resilient
Smaller resources footprint
Hedge Clients

62
With Spring, you can start writing your app with WebMVC,
introduce WebClient to improve backend calls workflows,
then consider moving to WebFlux

63
Write an Edge API
Available
Traffic Control
Volume of Connections

64
Write an Edge API
Available
Traffic Control
Volume of Connections

65
Traffic Control
A reactive runtime will isolate ingress/egress traffic latency
and exceptions.
Given this isolation property, a reactive Edge API should
always be able to route traffic, even limit it or short-circuit
when required.

66
Mobile Backend
Scale with different traffic latency
Connected experience (notifications…)
Volume of clients

67
Mobile IoT Backend
Scale with different traffic latency
Volume of clients

Ok sounds cool, but what about the
developer experience ?
68
😷

69
Error has been observed at the following site(s):
|_ checkpoint ⇢ Handler io.spring.workshop.tradingservice.QuotesController#quotesDetails(String) [DispatcherHandler]
|_ checkpoint ⇢ org.springframework.security.web.server.authorization.AuthorizationWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.authorization.ExceptionTranslationWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.authentication.logout.LogoutWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.savedrequest.ServerRequestCacheWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.context.SecurityContextServerWebExchangeWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.ui.LogoutPageGeneratingWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.ui.LoginPageGeneratingWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.authentication.AuthenticationWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.authentication.AuthenticationWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.context.ReactorContextWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.csrf.CsrfWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.header.HttpHeaderWriterWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.conﬁg.web.server.ServerHttpSecurity$ServerWebExchangeReactorContextWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.security.web.server.WebFilterChainProxy [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.boot.web.reactive.ﬁlter.OrderedHiddenHttpMethodFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.boot.actuate.metrics.web.reactive.server.MetricsWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ HTTP GET "/quotes/summary/MSFT" [ExceptionHandlingWebHandler]
Exceptions since Spring Framework 5.2
Actionable stacktraces

70
|_ Mono.doOnNext ⇢ at io.spring.workshop.tradingservice.TradingCompanyClient.getTradingCompany(TradingCompanyClient.java:38)
|_ Mono.switchIfEmpty ⇢ at io.spring.workshop.tradingservice.TradingCompanyClient.getTradingCompany(TradingCompanyClient.java:39)
|_ Mono.zipWith ⇢ at io.spring.workshop.tradingservice.QuotesController.quotesDetails(QuotesController.java:39)
|_ Mono.switchIfEmpty ⇢ at org.springframework.http.codec.EncoderHttpMessageWriter.write(EncoderHttpMessageWriter.java:119)
|_ Mono.flatMap ⇢ at org.springframework.http.codec.EncoderHttpMessageWriter.write(EncoderHttpMessageWriter.java:123)
|_ Mono.flatMap ⇢ at org.springframework.web.reactive.DispatcherHandler.lambda$handleResult$5(DispatcherHandler.java:172)
|_ Mono.onErrorResume ⇢ at org.springframework.web.reactive.DispatcherHandler.handleResult(DispatcherHandler.java:171)
|_ Mono.flatMap ⇢ at org.springframework.web.reactive.DispatcherHandler.handle(DispatcherHandler.java:147)
|_ Mono.defer ⇢ at org.springframework.web.server.handler.DefaultWebFilterChain.filter(DefaultWebFilterChain.java:119)
|_ Mono.switchIfEmpty ⇢ at org.springframework.security.web.server.authorization.AuthorizationWebFilter.filter(AuthorizationWebFilter.java:46)
|_ FluxMap$MapSubscriber.onComplete ⇢ at reactor.netty.channel.FluxReceive.terminateReceiver(FluxReceive.java:391)
Exceptions with debug mode enabled

71
|_ Mono.doOnNext ⇢ at io.spring.workshop.tradingservice.TradingCompanyClient.getTradingCompany(TradingCompanyClient.java:38)
|_ Mono.switchIfEmpty ⇢ at io.spring.workshop.tradingservice.TradingCompanyClient.getTradingCompany(TradingCompanyClient.java:39)
|_ Mono.zipWith ⇢ at io.spring.workshop.tradingservice.QuotesController.quotesDetails(QuotesController.java:39)
|_ Mono.switchIfEmpty ⇢ at org.springframework.http.codec.EncoderHttpMessageWriter.write(EncoderHttpMessageWriter.java:119)
|_ Mono.flatMap ⇢ at org.springframework.http.codec.EncoderHttpMessageWriter.write(EncoderHttpMessageWriter.java:123)
|_ Mono.flatMap ⇢ at org.springframework.web.reactive.DispatcherHandler.lambda$handleResult$5(DispatcherHandler.java:172)
|_ Mono.onErrorResume ⇢ at org.springframework.web.reactive.DispatcherHandler.handleResult(DispatcherHandler.java:171)
|_ Mono.flatMap ⇢ at org.springframework.web.reactive.DispatcherHandler.handle(DispatcherHandler.java:147)
|_ Mono.switchIfEmpty ⇢ at org.springframework.security.web.server.authorization.AuthorizationWebFilter.filter(AuthorizationWebFilter.java:46)
|_ FluxMap$MapSubscriber.onComplete ⇢ at reactor.netty.channel.FluxReceive.terminateReceiver(FluxReceive.java:391)
Exceptions with debug mode enabled
Reactive Developer productivity

72
Soon coming as a jvm agent
Mobile Backend
Scale even with different traffic latency
Volume of clients

73
Soon coming as a jvm agent
Mobile Backend
Volume of clients
Speaking of which…

74
BlockHound !
Mobile Backend
Volume of clients
https://github.com/reactor/BlockHound

Detecting blocking code in reactive stack
75
BlockHound.install();
.getBody();
});

Detecting blocking code in reactive stack
76
BlockHound.install();
.getBody();
});
java.lang.Error: Blocking call! java.net.Socket#connect
at reactor.blockhound.BlockHound$Builder.lambda$new$0(BlockHound.java:154)
~[blockhound-1.0.0.jar:na]
at reactor.blockhound.BlockHound$Builder.lambda$install$8(BlockHound.java:254)
at reactor.blockhound.BlockHoundRuntime.checkBlocking(BlockHoundRuntime.java:43)
at java.net.Socket.connect(Socket.java) ~[na:1.8.0_144]
at sun.net.NetworkClient.doConnect(NetworkClient.java:180) ~[na:1.8.0_144]
at sun.net.www.http.HttpClient.openServer(HttpClient.java:463) ~[na:1.8.0_144]
at sun.net.www.http.HttpClient.openServer(HttpClient.java:558) ~[na:1.8.0_144]
at sun.net.www.http.HttpClient.<init>(HttpClient.java:242) ~[na:1.8.0_144]
at sun.net.www.http.HttpClient.New(HttpClient.java:339) ~[na:1.8.0_144]
at sun.net.www.http.HttpClient.New(HttpClient.java:357) ~[na:1.8.0_144]
Quickly detect during pre-production
workflows that will likely degrade your
reactive stack experience

More reactive microservices ?
77
🤗

~80% of apps generated by start.spring.io are using a SQL driver
78

~80% of apps generated by start.spring.io are using a SQL driver
79
r2dbc.io

What should I look after I successfully have written my first Reactive apps ?
80

Monitoring with Micrometer
81
micrometer.io

82
Networking with RSocket
rsocket.io

83
Having fun developing with Kotlin
kotlinlang.org

85
[…]
With Reactive
You can actually be more productive in
writing state of the art, scalable
microservices

86
[…]
With Reactive
Your Applications are designed to be
resilient under stress and lower
maintenance

87
[…]
With Reactive
You run more for less

88
[…]

89
Establish the right project to experiment
Reactive Programming with

90
Do it progressively, migrate a few dedicated
backend routes then an entire application
You can already parallelize some workloads
even on your blocking stack

92
Use all the developers tools you can to
accelerate your reactive adoption and
build trust

93
Once the cost of learning has been paid
and the benefits realized- it’s usually
difficult to come back to blocking solutions.

94
In fact it’s difficult in today’s world of
distributed systems to not find a reason
for giving a go to any Reactive stack.

95
In fact it’s difficult in today’s world of
distributed systems to not find a reason
for giving a go to any Reactive stack.
It’s just designed for them

The Value of Reactive

Related slideshows

More Related Content

The Value of Reactive