使用非流应用程序/ json的Spring WebFlux Flux行为

2019-10-02 09:21:04 阅读：205 来源： 互联网

我正在使用Spring Webflux进行评估,但我们必须支持期望application / json的客户端,而不是application / stream json.我不清楚Spring WebFlux如何处理需要application / json的客户端序列化Flux.

如果一个Flux被序列化为application / json而不是application / stream json,它是一个阻塞操作吗？

下面我整理了一个样本控制器来演示我所看到的内容.当流是无限的并且生成application / json时,没有任何内容返回给浏览器.这似乎是合理的,因为它可能正在等待流终止.当流是无限的并且生成应用程序/流json时,我按预期在浏览器中连续看到JSON对象.当Flux是有限的时,比如100个元素,类型是application / json,它会一次性地呈现出来.问题是,它是否必须等待Flux在序列化之前终止,并且这会导致阻塞操作.返回正常的application / json时,使用Flux对性能和可伸缩性有什么影响？

@RestController
public class ReactiveController {

    /* Note: In the browser this sits forever and never renders */
    @GetMapping(path = "/nonStreaming", produces = MediaType.APPLICATION_JSON_VALUE)
    public Flux<Person> getPeopleNonStreaming() {
        return Flux.interval(Duration.ofMillis(100))
                .map(tick -> new Person("Dude", "Dude", tick));
    }

    /* Note: This renders in the browser in chunks forever */
    @GetMapping(path = "/streaming", produces = MediaType.APPLICATION_STREAM_JSON_VALUE)
    public Flux<Person> getPeopleStreaming() {
        return Flux.interval(Duration.ofMillis(100))
                .map(tick -> new Person("Dude", "Dude", tick));
    }

    /* Note: This returns, but I can't tell if it is done in a non blocking manner. It
     * appears to gather everything before serializing. */
    @GetMapping(path = "/finiteFlux", produces = MediaType.APPLICATION_JSON_VALUE)
    public Flux<Person> finiteFlux() {
        return Flux.range(0, 100)
                .map(tick -> new Person("Dude", "Dude", tick));
    }
}

更新：

我在下面添加了其他日志记录信息：

流式传输似乎使用两个不同的线程

2019-02-13 16:53:07.363 DEBUG 3416 --- [ctor-http-nio-2] o.s.w.s.adapter.HttpWebHandlerAdapter    : [dac80fd4] HTTP GET "/streaming"
2019-02-13 16:53:07.384 DEBUG 3416 --- [ctor-http-nio-2] s.w.r.r.m.a.RequestMappingHandlerMapping : [dac80fd4] Mapped to public reactor.core.publisher.Flux<io.jkratz.reactivedemo.Person> io.jkratz.reactivedemo.ReactiveController.getPeopleStreaming()
2019-02-13 16:53:07.398 DEBUG 3416 --- [ctor-http-nio-2] o.s.w.r.r.m.a.ResponseBodyResultHandler  : Using 'application/stream+json;q=0.8' given [text/html, application/xhtml+xml, image/webp, image/apng, application/xml;q=0.9, */*;q=0.8] and supported [application/stream+json]
2019-02-13 16:53:07.398 DEBUG 3416 --- [ctor-http-nio-2] o.s.w.r.r.m.a.ResponseBodyResultHandler  : [dac80fd4] 0..N [io.jkratz.reactivedemo.Person]
2019-02-13 16:53:07.532 DEBUG 3416 --- [     parallel-1] o.s.http.codec.json.Jackson2JsonEncoder  : [dac80fd4] Encoding [io.jkratz.reactivedemo.Person@6b3e843d]
2019-02-13 16:53:07.566 DEBUG 3416 --- [ctor-http-nio-2] r.n.channel.ChannelOperationsHandler     : [id: 0xdac80fd4, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:52398] Writing object DefaultHttpResponse(decodeResult: success, version: HTTP/1.1)
HTTP/1.1 200 OK
transfer-encoding: chunked
Content-Type: application/stream+json;q=0.8;charset=UTF-8
2019-02-13 16:53:07.591 DEBUG 3416 --- [ctor-http-nio-2] r.n.channel.ChannelOperationsHandler     : [id: 0xdac80fd4, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:52398] Writing object 
2019-02-13 16:53:07.629 DEBUG 3416 --- [     parallel-1] o.s.http.codec.json.Jackson2JsonEncoder  : [dac80fd4] Encoding [io.jkratz.reactivedemo.Person@217d62db]
2019-02-13 16:53:07.630 DEBUG 3416 --- [ctor-http-nio-2] r.n.channel.ChannelOperationsHandler     : [id: 0xdac80fd4, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:52398] Writing object 
2019-02-13 16:53:07.732 DEBUG 3416 --- [     parallel-1] o.s.http.codec.json.Jackson2JsonEncoder  : [dac80fd4] Encoding [io.jkratz.reactivedemo.Person@741c0c88]
2019-02-13 16:53:07.732 DEBUG 3416 --- [ctor-http-nio-2] r.n.channel.ChannelOperationsHandler     : [id: 0xdac80fd4, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:52398] Writing object 
2019-02-13 16:53:07.832 DEBUG 3416 --- [     parallel-1] o.s.http.codec.json.Jackson2JsonEncoder  : [dac80fd4] Encoding [io.jkratz.reactivedemo.Person@7b8532e5]

虽然有限的JSON只使用单个线程.

2019-02-13 16:55:34.431 DEBUG 3416 --- [ctor-http-nio-3] o.s.w.s.adapter.HttpWebHandlerAdapter    : [5b048f46] HTTP GET "/finiteFlux"
2019-02-13 16:55:34.432 DEBUG 3416 --- [ctor-http-nio-3] s.w.r.r.m.a.RequestMappingHandlerMapping : [5b048f46] Mapped to public reactor.core.publisher.Flux<io.jkratz.reactivedemo.Person> io.jkratz.reactivedemo.ReactiveController.finiteFlux()
2019-02-13 16:55:34.434 DEBUG 3416 --- [ctor-http-nio-3] o.s.w.r.r.m.a.ResponseBodyResultHandler  : Using 'application/json;q=0.8' given [text/html, application/xhtml+xml, image/webp, image/apng, application/xml;q=0.9, */*;q=0.8] and supported [application/json]
2019-02-13 16:55:34.435 DEBUG 3416 --- [ctor-http-nio-3] o.s.w.r.r.m.a.ResponseBodyResultHandler  : [5b048f46] 0..N [io.jkratz.reactivedemo.Person]
2019-02-13 16:55:34.439 DEBUG 3416 --- [ctor-http-nio-3] o.s.http.codec.json.Jackson2JsonEncoder  : [5b048f46] Encoding [[io.jkratz.reactivedemo.Person@425c8296, io.jkratz.reactivedemo.Person@22ae73df, io.jkratz.reactived (truncated)...]
2019-02-13 16:55:34.448 DEBUG 3416 --- [ctor-http-nio-3] r.n.channel.ChannelOperationsHandler     : [id: 0x5b048f46, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:52991] Writing object DefaultHttpResponse(decodeResult: success, version: HTTP/1.1)
HTTP/1.1 200 OK
transfer-encoding: chunked
Content-Type: application/json;q=0.8;charset=UTF-8
2019-02-13 16:55:34.448 DEBUG 3416 --- [ctor-http-nio-3] r.n.channel.ChannelOperationsHandler     : [id: 0x5b048f46, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:52991] Writing object 
2019-02-13 16:55:34.450 DEBUG 3416 --- [ctor-http-nio-3] o.s.w.s.adapter.HttpWebHandlerAdapter    : [5b048f46] Completed 200 OK
2019-02-13 16:55:34.450 DEBUG 3416 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations     : [id: 0x5b048f46, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:52991] Last HTTP response frame
2019-02-13 16:55:34.450 DEBUG 3416 --- [ctor-http-nio-3] r.n.channel.ChannelOperationsHandler     : [id: 0x5b048f46, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:52991] Writing object EmptyLastHttpContent
2019-02-13 16:55:34.450 DEBUG 3416 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations     : [id: 0x5b048f46, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:52991] Decreasing pending responses, now 0
2019-02-13 16:55:34.451 DEBUG 3416 --- [ctor-http-nio-3] r.n.channel.ChannelOperationsHandler     : [id: 0x5b048f46, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:52991] No ChannelOperation attached. Dropping: EmptyLastHttpContent

解决方法:

在流式mimetype(应用程序/流json)的情况下,Spring WebFlux中默认配置的JSON编解码器将序列化为JSON并在网络上刷新Flux输入的每个元素.当流是无限的时,或者当您希望在可用时立即将信息推送到客户端时,此行为很方便.请注意,这会产生性能成本,因为调用序列化程序并多次刷新会占用资源.

在非流式类型(application / json)的情况下,Spring WebFlux中默认配置的JSON编解码器将序列化为JSON并一次性刷新到网络.它将缓冲Flux< YourObject>在内存中并一次性序列化它.
这并不意味着操作是阻塞的,因为得到的Flux< Databuffer>以反应的方式写入网络.这里什么都没有阻止.

这只是“流数据和使用更多资源”与“更有效地缓冲和使用资源”之间的权衡.

在流式传输的情况下,事物更可能由不同的工作线程处理,因为工作项以不同的间隔可用.在简单的JSON响应的情况下 – 它也可能由一个或多个线程处理：它取决于有效负载大小,如果远程客户端是否缓慢.

标签：spring-webflux,reactor,spring
来源： https://codeday.me/bug/20191002/1842082.html

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使用非流应用程序/ json的Spring WebFlux Flux行为