fun connectionConnectionAcquired(connection: RealConnection)

  fun connectionConnectionReleased(connection: RealConnection)

  fun connectionConnectionClosed(connection: RealConnection)

  fun noNewExchanges(connection: RealConnection)

  fun doExtensiveHealthChecks(): Boolean

  fun isCanceled(): Boolean

  fun candidateConnection(): RealConnection?

  fun proxySelectStart(url: HttpUrl)

    val call: Call,
  ) : ConnectionEvent() {
    override fun closes(event: ConnectionEvent): Boolean =
      event is ConnectionAcquired && connection == event.connection && call == event.call
  }

  data class NoNewExchanges(
    override val timestampNs: Long,
    override val connection: Connection,
  ) : ConnectionEvent()

    }
    assertThat(listener.recordedEventTypes()).containsExactly(
      "ConnectStart",
      "ConnectEnd",
      "ConnectionAcquired",
      "NoNewExchanges",
      "ConnectionReleased",
      "ConnectionClosed",
    )
  }

  @Throws(IOException::class)
  private fun assertSuccessfulEventOrder() {
    val call =
      client.newCall(

    return connection
  }

  override fun trackFailure(
    call: RealCall,
    e: IOException?,
  ) {
    // Do nothing.
  }

  override fun noNewExchanges() {
    // Do nothing.
  }

  override fun cancel() {
    canceled = true
    // Close the raw socket so we don't end up doing synchronous I/O.
    rawSocket?.closeQuietly()
  }

#### Per-Connection Locks

Each connection has its own lock. The connections in the pool are all in a `ConcurrentLinkedQueue`. Due to data races, iterators of this queue may return removed connections. Callers must check the connection's `noNewExchanges` property before using connections from the pool.

The connection lock is never held while doing I/O (even closing a socket) to prevent contention.

      override val sink = RequestBodySink(codec.socket.sink, -1L)
      override val source = ResponseBodySource(codec.socket.source, -1L)
    }
  }

  fun noNewExchangesOnConnection() {
    codec.carrier.noNewExchanges()
  }

  fun cancel() {
    codec.cancel()
  }

  /**
   * Revoke this exchange's access to streams. This is necessary when a follow-up request is

    awaitGarbageCollection()
    assertThat(pool.closeConnections(100L)).isEqualTo(0L)
    assertThat(c1.calls).isEmpty()

    // Can't allocate once a leak has been detected.
    assertThat(c1.noNewExchanges).isTrue()
  }

  @Test fun interruptStopsThread() {
    val taskRunnerThreads = mutableListOf<Thread>()
    val taskRunner =
      TaskRunner(
        RealBackend { runnable ->