处理 Kotlin 中的 Spring WebFlux WebClient 超时

Question

I am doing a get http call with Spring WebFlux WebClient (Boot 2.4.3) in Kotlin (1.4.30). When request times out it fails with exception but instead I'd like to return a default value. I see references to onError , onStatus etc. used after retrieve() but they don't seem to be available in my case (only body , toEntity , awaitExchange )

The call:

suspend fun conversation(id: String): Conversation =
    client.get().uri("/conversation/{id}", id).retrieve().awaitBody()

WebClient configuration with connect and read timeouts:

fun webClient(url: String, connectTimeout: Int, readTimeout: Long, objectMapper: ObjectMapper): WebClient =
    WebClient.builder()
      .baseUrl(url)
      .exchangeStrategies(
        ExchangeStrategies.builder()
          .codecs { configurer -> configurer.defaultCodecs().jackson2JsonDecoder(Jackson2JsonDecoder(objectMapper)) }
          .build())
      .clientConnector(
        ReactorClientHttpConnector(
          HttpClient.create()
            .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, connectTimeout)
            .doOnConnected { connection ->
              connection.addHandlerLast(ReadTimeoutHandler(readTimeout, TimeUnit.MILLISECONDS))
            }))
      .build()

Response model:

@JsonIgnoreProperties(ignoreUnknown = true)
data class Conversation(
  val replyTimestamp: Map<String, String>,
)

How can I return default response (conversation with empty map) in case of timeout instead of failing with an exception?

Update:

I tried suggestion of JArgente below: updated the call with awaitExchange and set valid WireMock response with delay (1010 ms) that is longer that timeout (1000 ms).

Result is still ReadTimeoutException so looking at http status code does not help in this case.

  private val defaultConversation = Conversation(emptyMap())

  suspend fun conversation(id: String): Conversation =
    client.get()
      .uri("/conversation/{id}", id)
      .awaitExchange {
          response -> if (response.statusCode() == HttpStatus.OK)  response.awaitBody() else defaultConversation
      }

Response:

{
  "replyTimestamp": {
    "1": "2021-02-23T15:30:28.753Z",
    "2": "2021-02-23T16:30:28.753Z"
  }
}

Mock config for it:

{
  "mappings":
  [
    {
      "priority": 1,
      "request": {
        "method": "GET",
        "urlPathPattern": "/conversation/1"
      },
      "response": {
        "status": 200,
        "fixedDelayMilliseconds": 1010,
        "headers": {
          "content-type": "application/json;charset=utf-8"
        },
        "bodyFileName": "conversation1.json"
      }
    }
  ]
}

Answer 1

You are getting an exception because in your method, you are expecting to get a response of type Conversation, but because you are receiving an error, the body is different. The way you should handle the response, in this case, should be first, to look at the HTTP status code and then convert the body accordingly. Here is an example from spring.io https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html

In your case, when you receive the status code of the error you should create a new empty Conversation and return it

val entity = client.get()
  .uri("/conversation/{id}", id)
  .accept(MediaType.APPLICATION_JSON)
  .awaitExchange {
        if (response.statusCode() == HttpStatus.OK) {
             return response.awaitBody<Conversation>()
        }
        else if (response.statusCode().is4xxClientError) {
             return response.awaitBody<ErrorContainer>()
        }
        else {
             throw response.createExceptionAndAwait()
        }
  }

Answer 2

As per Martin's suggestion ended up just wrapping call in a try/catch:

suspend inline fun <reified T : Any> WebClient.ResponseSpec.tryAwaitBodyOrElseLogged(default: T, log: Logger) : T =
  try {
    awaitBody()
  } catch (e: Exception) {
    log.warn("Remote request failed, returning default value ($default)", e)
    default
  }

private val log = LoggerFactory.getLogger(this::class.java)
private val default = Conversation(emptyMap())

suspend fun conversation(id: String): Conversation =
  client.get()
    .uri("/conversation/{id}", id)
    .retrieve()
    .tryAwaitBodyOrElseLogged(default, log)

I thought there is some idiomatic way but this works fine.