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Rossen Stoyanchev
S e r v l e t v s R e a c t i v e
5 use cases
stacks
in
Servlet Stack
- Servlet container
- Servlet API
- Spring MVC
Reactive Stack
- Netty, Servlet 3.1+, Undertow
- Reactive Streams
- Spring WebFlux
S e r v l e t v s R e a c t i v e in 5 use cases - - PowerPoint PPT Presentation
S e r v l e t v s R e a c t i v e in 5 use cases - - PowerPoint PPT Presentation
stacks S e r v l e t v s R e a c t i v e in 5 use cases Rossen Stoyanchev Servlet Stack Reactive Stack Servlet container Netty, Servlet 3.1+, Undertow Servlet API Reactive Streams Spring MVC Spring
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Reactive Spring
Reactive starters in Spring Boot 2.0 Spring Framework 5 WebFlux endpoints + reactive WebClient Reactive Spring Data Kay repositories Spring Security and more…
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Servlet Stack
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Filter Filter Controller Spring MVC
Servlet API
container thread
SERVLET STACK
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Synchronous API Filter, Servlet … void
SERVLET STACK
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Blocking I/O InputStream, OutputStream
SERVLET STACK
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servletRequest.startAsync()
SERVLET STACK
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Filter Controller Filter Servlet
SERVLET STACK SERVLET STACK
Filter Controller Filter Servlet
… do work or receive event + dispatch()…
container- thread-1 container- thread-2
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Servlet API Container thread pool Controller
SERVLET STACK
can use reactive clients
Input & OutputStream startAsync()
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Concurrency models Concurrency Concurrency Concurrency
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“elastic” thread pool “parallel” thread pool
100s, 1000s waiting blocked threads ~ per CPU core busy worker threads
Synchronous APIs Non-blocking code
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What does it take to not block ?
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event loop at the core
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event driven architecture message passing
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means to compose async logic
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bonus: back pressure (a.k.a flow control)
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Reactive Stack
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Spring WebFlux Web Filter NO BLOCKING ANY TIME Controller Reactive Server Adapter Web Filter
HTTP Server Event Loop
REACTIVE STACK
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Asynchronous API WebFilter, WebHandler… Mono<Void>
REACTIVE STACK
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REACTIVE STACK
Reactor Mono Reactive Streams Publisher 0..1 elements
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Non-blocking read: Flux<DataBuffer> getBody()
REACTIVE STACK
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Non-blocking write: writeWith(Flux<DataBuffer>)
REACTIVE STACK
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REACTIVE STACK
Reactor Flux Reactive Streams Publisher 0..N elements
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request(1)
- nNext(item)
Flux
Reactive Streams back pressure
request(1)
- nNext(item)
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request(n)
- nNext(item)
F
Mono
E
Flux
D
Mono
C
Mono
B
Controller Spring WebFlux WebFilter
Composition of async logic
Mono
A A B C E F D Actual processing
HTTP Server Event Loop
REACTIVE STACK
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repository
Use Case #1
data Reactive
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Demo
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HTTP GET with reactive data repository
Designed to work on both Spring MVC and Spring WebFlux Simply return reactive type (Flux, Observable) from @Controller
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Flux<T>:
finite collection or infinite stream?
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Use media type to decide
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“application/json”
finite collection (JSON array)
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No back pressure: Flux#collectToList (request all + buffer)
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Use Case #2
back pressure
with
R e s p
- n
s e s t r e a m
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“text/event-stream”, “application/stream+json”
infinite stream
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Back pressure:
request(n), write, flush, repeat
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HTTP GET with streaming response
Simply return reactive type (Flux, Observable) from @Controller Back pressure on Spring MVC and WebFlux
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Servlet Container Servlet API Spring MVC Flux
Back pressure against blocking OutputStream
Controller Flux Data Repository
- nNext(T)
- nNext(T)
Blocking write on MvcAsync thread pool
request(n) request(1)
SERVLET STACK …
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Servlet 3.1 non-blocking I/O ?
Unlike Servlet 3.0 async, Servlet 3.1 non-blocking is hard to retrofit Requires deeper change Mutually exclusive with rest of the Servlet API
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HTTP Server Server Adapter Flux Spring WebFlux Flux
Response streaming on reactive stack
Controller Flux Data Repo
- nNext(T)
- nNext(T)
- nNext(T)
Non-blocking write back pressure to socket
request(n) request(n) request(n)
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Demo
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Use Case #3
remote service
- r
c h e s t r a t i
- n
Reactive
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Demo
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Orchestrate non-blocking, nested remote service calls with ease Similar to reactive data access Spring MVC and Spring WebFlux
Reactive WebClient
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Use Case #4
request input Reactive
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Back pressure to socket
No reading until reactive demand signalled from upstream Non-blocking Reactive stack only territory !
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HTTP POST with data
@RequestBody argument with reactive type (Mono, Single) Reactive type is not required
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Use Case #5
Data Ingestion back pressure
w i t h
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Media type indicates infinite stream is expected Non-blocking streaming + back pressure
HTTP POST with stream of data
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HTTP Server Server Adapter Flux Spring WebFlux Flux
Data ingestion on reactive stack
Controller
- nNext(T)
- nNext(T)
Non-blocking read back pressure from socket
request(n) request(n)
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Servlet stack summary
Reactive data repository Streaming to the response with back pressure Reactive orchestration of remote services Reactive request input Data ingestion with back pressure
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Reactive stack summary
Reactive data repository Streaming to the response with back pressure Reactive orchestration of remote services Reactive request input Data ingestion with back pressure
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Q & A
@rstoya05