}

  override fun connectionConnectionClosed(connection: RealConnection) {
    connection.connectionListener.connectionClosed(connection)
  }

  override fun noNewExchanges(connection: RealConnection) {
    connection.connectionListener.noNewExchanges(connection)
  }

  override fun doExtensiveHealthChecks(): Boolean = chain.request.method != "GET"

  override fun isCanceled(): Boolean = call.isCanceled()

   */
  interface Carrier {
    val route: Route

    fun trackFailure(
      call: RealCall,
      e: IOException?,
    )

    fun noNewExchanges()

    fun cancel()
  }

  companion object {
    /**
     * The timeout to use while discarding a stream of input data. Since this is used for connection

      if (connection.noNewExchanges) {
        assertThat(eventSequence).matchesPredicate { deque ->
          deque.any { it is NoNewExchanges && it.connection == connection }
        }
      }
    }

    logEvent(ConnectionEvent.ConnectionReleased(System.nanoTime(), connection, call))
  }

  }

  override fun connectionConnectionReleased(connection: RealConnection) {
  }

  override fun connectionConnectionClosed(connection: RealConnection) {
  }

  override fun noNewExchanges(connection: RealConnection) {
  }

  override fun doExtensiveHealthChecks(): Boolean = false

  override fun isCanceled(): Boolean = false

  override fun candidateConnection(): RealConnection? = null

   */
  open fun connectionReleased(
    connection: Connection,
    call: Call,
  ) {}

  /**
   * Invoked when a connection is marked for no new exchanges.
   */
  open fun noNewExchanges(connection: Connection) {}

  companion object {
    val NONE: ConnectionListener = object : ConnectionListener() {}
  }

  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()

#### 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