return null
        }

        if (retryAfter(userResponse, Integer.MAX_VALUE) == 0) {
          // specifically received an instruction to retry without delay
          return userResponse.request
        }

        return null
      }

      HTTP_MISDIRECTED_REQUEST -> {

      eachQueue@ for (queue in readyQueues) {
        val candidate = queue.futureTasks[0]
        val candidateDelay = maxOf(0L, candidate.nextExecuteNanoTime - now)

        when {
          // Compute the delay of the soonest-executable task.
          candidateDelay > 0L -> {
            minDelayNanos = minOf(candidateDelay, minDelayNanos)
            continue@eachQueue
          }

    sink.writeUtf8(data)
    sink.close()
    return result
  }

  private fun cancelLater(
    call: Call,
    delay: Long,
  ): Thread {
    val thread =
      object : Thread("canceler") {
        override fun run() {
          try {
            sleep(delay)
          } catch (e: InterruptedException) {
            throw AssertionError()
          }
          call.cancel()

            }
          }
        }
      }

      // Update the connection flow control, as this is a shared resource.
      // Even if our stream doesn't need more data, others might.
      // But delay updating the stream flow control until that stream has been
      // consumed
      updateConnectionFlowControl(byteCount)

      // Notify that buffer size changed

  ) {
    setUp(protocol, mockWebServer)
    // Ping every 500 ms, starting at 500 ms.
    client =
      client.newBuilder()
        .pingInterval(Duration.ofMillis(500))
        .build()

    // Delay the response to give 1 ping enough time to be sent and replied to.
    server.enqueue(
      MockResponse.Builder()
        .bodyDelay(750, TimeUnit.MILLISECONDS)
        .body("ABC")
        .build(),
    )

      "FINE: Q10000 finished run in   0 µs: task",
      "FINE: Q10000 starting              : task",
      "FINE: Q10000 finished run in   0 µs: task",
    )
  }

  /** Repeat with a delay of 200 but schedule with a delay of 50. The schedule wins. */
  @Test fun executeScheduledEarlierReplacesRepeatedLater() {
    val task =
      object : Task("task") {
        val schedules = mutableListOf(50.µs)

    source.close()
    assertThat(relay.isClosed).isTrue()
    assertFile(Relay.PREFIX_CLEAN, 13L, metadata.size, "abcdefghijklm", metadata)
  }

  @Test
  fun multipleSources() {
    val upstream = Buffer()
    upstream.writeUtf8("abcdefghijklm")
    val relay = edit(file, upstream, metadata, 1024)
    val source1 = relay.newSource()!!.buffer()
    val source2 = relay.newSource()!!.buffer()

 *
 * This test uses [TaskFaker] to deterministically test racy code. Each function in this test has
 * the same structure:
 *
 *  * prepare a set of plans, each with a predictable connect delay
 *  * attempt to find a connection
 *  * step through time, asserting that the expected side effects are performed.
 */
internal class FastFallbackExchangeFinderTest {
  private val taskFaker = TaskFaker()