如何在Spring WebFlux中记录请求和响应正文

问题描述：

我想在带有Kotlin的Spring WebFlux上的REST API中集中记录请求和响应.到目前为止，我已经尝试过这种方法

I want to have centralised logging for requests and responses in my REST API on Spring WebFlux with Kotlin. So far I've tried this approaches

@Bean
fun apiRouter() = router {
    (accept(MediaType.APPLICATION_JSON) and "/api").nest {
        "/user".nest {
            GET("/", userHandler::listUsers)
            POST("/{userId}", userHandler::updateUser)
        }
    }
}.filter { request, next ->
    logger.info { "Processing request $request with body ${request.bodyToMono<String>()}" }
    next.handle(request).doOnSuccess { logger.info { "Handling with response $it" } }
}

这里请求方法和路径已成功记录，但正文为Mono，那么我应该如何记录呢?是否应该相反，我必须订阅请求正文Mono并将其记录在回调中? 另一个问题是，这里的ServerResponse接口无法访问响应主体.我怎么在这里买?

Here request method and path log successfully but the body is Mono, so how should I log it? Should it be the other way around and I have to subscribe on request body Mono and log it in the callback? Another problem is that ServerResponse interface here doesn't have access to the response body. How can I get it here?

我尝试过的另一种方法是使用WebFilter

Another approach I've tried is using WebFilter

@Bean
fun loggingFilter(): WebFilter =
        WebFilter { exchange, chain ->
            val request = exchange.request
            logger.info { "Processing request method=${request.method} path=${request.path.pathWithinApplication()} params=[${request.queryParams}] body=[${request.body}]"  }

            val result = chain.filter(exchange)

            logger.info { "Handling with response ${exchange.response}" }

            return@WebFilter result
        }

这里有同样的问题:请求正文是Flux，没有响应正文.

Same problem here: request body is Flux and no response body.

是否可以通过某些过滤器访问完整的请求和响应以进行日志记录?我不明白吗?

Is there a way to access full request and response for logging from some filters? What don't I understand?

答

这与Spring MVC中的情况或多或少相似.

This is more or less similar to the situation in Spring MVC.

在Spring MVC中，可以使用AbstractRequestLoggingFilter过滤器和ContentCachingRequestWrapper和/或ContentCachingResponseWrapper.这里有很多折衷:

In Spring MVC, you can use a AbstractRequestLoggingFilter filter and ContentCachingRequestWrapper and/or ContentCachingResponseWrapper. Many tradeoffs here:

如果您想访问servlet请求属性，则需要实际读取并解析请求正文
记录请求正文意味着缓冲请求正文，这可能会占用大量内存
如果要访问响应正文，则需要包装响应并在编写响应正文时对其进行缓冲，以供以后检索

ContentCaching*Wrapper类在WebFlux中不存在，但是您可以创建类似的类.但是请记住这里的其他要点:

ContentCaching*Wrapper classes don't exist in WebFlux but you could create similar ones. But keep in mind other points here:

在内存中缓冲数据以某种方式违反了反应堆，因为我们正在尝试使用可用资源来提高效率
您不应该篡改实际的数据流，并且不应该频繁/频繁地刷新数据，否则就有可能破坏流式传输用例的风险
中，您只能访问DataBuffer实例，这些实例(大约)是内存有效的字节数组.这些属于缓冲池，并被回收以用于其他交换.如果未正确保留/释放这些内存，则会造成内存泄漏(并且缓冲数据以供日后使用肯定适合这种情况)

buffering data in memory somehow goes against the reactive stack, since we're trying there to be very efficient with the available resources
you should not tamper with the actual flow of data and flush more/less often than expected, otherwise you'd risk breaking streaming uses cases
at that level, you only have access to DataBuffer instances, which are (roughly) memory-efficient byte arrays. Those belong to buffer pools and are recycled for other exchanges. If those aren't properly retained/released, memory leaks are created (and buffering data for later consumption certainly fits that scenario)
again at that level, it's only bytes and you don't have access to any codec to parse the HTTP body. I'd forget about buffering the content if it's not human-readable in the first place

您问题的其他答案:

是的，WebFilter可能是最好的方法
不，您不应该订阅请求正文，否则您将消耗处理程序将无法读取的数据；您可以在请求上flatMap并在doOn运算符中缓冲数据
包装响应应该使您可以访问正在编写的响应正文；不过不要忘记内存泄漏

yes, the WebFilter is probably the best approach
no, you shouldn't subscribe to the request body otherwise you'd consume data that the handler won't be able to read; you can flatMap on the request and buffer data in doOn operators
wrapping the response should give you access to the response body as it's being written; don't forget about memory leaks, though

如何在Spring WebFlux中记录请求和响应正文

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