播放框架：如何处理 HTTP 过滤器中的服务器错误？

Question

我正在尝试创建一个 HTTP 过滤器，用于记录有关请求的一些信息，例如标头以及请求正文的有限（因此内存不会爆炸）部分，以防出现错误。

为此，我遵循了文档 (https://www.playframework.com/documentation/2.6.x/ScalaHttpFilters) 并提出了如下内容：

class RequestErrorLogFilter @Inject()(actorSystem: ActorSystem)(implicit ec: ExecutionContext)
  extends EssentialFilter {

  private val logger = org.slf4j.LoggerFactory.getLogger("application.AccumulatorFlowFilter")

  private implicit val logging = Logging(actorSystem.eventStream, logger.getName)

  override def apply(next: EssentialAction): EssentialAction = new EssentialAction {
    override def apply(request: RequestHeader): Accumulator[ByteString, Result] = {
      val accumulator: Accumulator[ByteString, Result] = next(request)

      val data = ArrayBuffer.empty[ByteString]
      var totalSize = 0
      val maxSize = 1024

      val flow: Flow[ByteString, ByteString, NotUsed] = Flow[ByteString]
        .map((in: ByteString) => {
          val left = maxSize - totalSize
          if (left > 0) {
            val takeNow =
              if (in.size > left) {
                in.slice(0, left)
              } else {
                in
              }
            data.append(takeNow)
            totalSize += takeNow.size
          }
          in
        })

      val accumulatorWithResult = accumulator.through(flow).map { result =>
        // this code doesn't get executed in case of an exception in a controller
        logger.info(s"The flow has completed and the result is $result")
        if (result.header.status >= 400) {
          val headerText = data.map(_.utf8String).mkString("")
          logger.warn(s"There was an error. Request head: $headerText")
        }
        result
      }

      accumulatorWithResult
    }
  }
}

这适用于客户端错误（如 400 - 错误请求）或控制器返回的任何错误，但如果控制器内部出现异常，则不会执行过滤器的“回调”，因此没有机会记录发生的事情。

还有一个更简单的“AccessLogHttpFilter”也有同样的问题，我认为这是使用播放应用程序创建访问日志的推荐解决方案：

class LoggingFilter @Inject() (val mat: Materializer, implicit val ec: ExecutionContext)
  extends Filter {

  def apply(nextFilter: RequestHeader => Future[Result])
           (requestHeader: RequestHeader): Future[Result] = {

    val startTime = System.currentTimeMillis

    nextFilter(requestHeader).map { result =>

      val endTime = System.currentTimeMillis
      val requestTime = endTime - startTime

      Logger.info(s"${requestHeader.method} ${requestHeader.uri} took ${requestTime}ms and " +
        s"returned ${result.header.status}")

      result.withHeaders("Request-Time" -> requestTime.toString)
    }
  }
}

有没有办法让 play 调用 http 过滤器代码，即使出现异常？ 还有其他解决方法吗？

Answer 1

想通了。

要让 EssentialFilter 处理错误，您需要向累加器添加 .recover() 调用：

class RequestErrorLogFilter @Inject()(actorSystem: ActorSystem)(implicit ec: ExecutionContext)
  extends EssentialFilter {

  private val logger = org.slf4j.LoggerFactory.getLogger("application.AccumulatorFlowFilter")

  private implicit val logging = Logging(actorSystem.eventStream, logger.getName)

  override def apply(next: EssentialAction): EssentialAction = new EssentialAction {
    override def apply(request: RequestHeader): Accumulator[ByteString, Result] = {
      val accumulator: Accumulator[ByteString, Result] = next(request)

      val data = ArrayBuffer.empty[ByteString]
      var totalSize = 0
      val maxSize = 1024

      val flow: Flow[ByteString, ByteString, NotUsed] = Flow[ByteString]
        .map((in: ByteString) => {
          val left = maxSize - totalSize
          if (left > 0) {
            val takeNow =
              if (in.size > left) {
                in.slice(0, left)
              } else {
                in
              }
            data.append(takeNow)
            totalSize += takeNow.size
          }
          in
        })

      val accumulatorWithResult: Accumulator[ByteString, Result] = accumulator.through(flow).map { result =>
        logger.info(s"The flow has completed and the result is $result")
        if (result.header.status >= 400) {
          val headerText = data.map(_.utf8String).mkString("")
          logger.warn(s"There was an error. Request head: $headerText")
        }
        result
      }

      accumulatorWithResult.recover {
        case error =>
          val headerText = data.map(_.utf8String).mkString("")
          logger.warn(s"There was an error: $error. Request head: $headerText")
          throw error
      }
    }
  }
}

对于一个简单的过滤器，您需要对结果future 调用 .failed.foreach：

class LoggingFilter @Inject() (val mat: Materializer, implicit val ec: ExecutionContext)
  extends Filter {

  def apply(nextFilter: RequestHeader => Future[Result])
           (requestHeader: RequestHeader): Future[Result] = {

    val startTime = System.currentTimeMillis

    val eventualResult = nextFilter(requestHeader)

    eventualResult.failed.foreach { error: Throwable =>
      val endTime = System.currentTimeMillis
      val requestTime = endTime - startTime

      Logger.info(s"${requestHeader.method} ${requestHeader.uri} took ${requestTime}ms and " +
        s"returned 500 $error")
    }

    eventualResult.map { result =>

      val endTime = System.currentTimeMillis
      val requestTime = endTime - startTime

      Logger.info(s"${requestHeader.method} ${requestHeader.uri} took ${requestTime}ms and " +
        s"returned ${result.header.status}")

      result.withHeaders("Request-Time" -> requestTime.toString)
    }
  }
}