spring - Spring WebClient：使用 WebFlux.fn + reactor-addons 重试

Question

我正在尝试WebClient使用 Kotlin Coroutines + WebFlux.fn + reactor-addons 添加条件重试：

suspend fun ClientResponse.asResponse(): ServerResponse =
    status(statusCode())
        .headers { headerConsumer -> headerConsumer.addAll(headers().asHttpHeaders()) }
        .body(bodyToMono(DataBuffer::class.java), DataBuffer::class.java)
        .retryWhen { 
            Retry.onlyIf { ctx: RetryContext<Throwable> -> (ctx.exception() as? WebClientResponseException)?.statusCode in retryableErrorCodes }
                .exponentialBackoff(ofSeconds(1), ofSeconds(5))
                .retryMax(3)
                .doOnRetry { log.error("Retry for {}", it.exception()) }
        )
        .awaitSingle()

还在重试之前添加条件

if (statusCode().isError) {
        body(
            BodyInserters.fromPublisher(
                Mono.error(StatusCodeError(status = statusCode())),
                StatusCodeException::class.java
            )
        )
    } else {
        body(bodyToMono(DataBuffer::class.java), DataBuffer::class.java)
    }

调用看起来像：

suspend fun request(): ServerResponse =
           webClient/*...*/
                    .awaitExchange()
                    .asResponse()

Answer 1

这个spring webclient：retry with backoff on specific error给了我回答这个问题的提示：

.awaitExchange()返回ClientResponse而不是Mono<ClientReponse> 这意味着我的重试正在执行bodyToMono而不是操作exchange()。

解决方案现在看起来像

suspend fun Mono<ClientResponse>.asResponse(): ServerResponse =
    flatMap {
        if (it.statusCode().isError) {
            Mono.error(StatusCodeException(status = it.statusCode()))
        } else {
            it.asResponse()
        }
    }.retryWhen(
        Retry.onlyIf { ctx: RetryContext<Throwable> ->
            (ctx.exception() as? StatusCodeException)?.shouldRetry() ?: false
        }
            .exponentialBackoff(ofSeconds(1), ofSeconds(5))
            .retryMax(3)
            .doOnRetry { log.error { it.exception() } }
    ).awaitSingle()

private fun ClientResponse.asResponse(): Mono<ServerResponse> =
    status(statusCode())
        .headers { headerConsumer -> headerConsumer.addAll(headers().asHttpHeaders()) }
        .body(bodyToMono(DataBuffer::class.java), DataBuffer::class.java)