internal constructor(
    maxIdleConnections: Int = 5,
    keepAliveDuration: Long = 5,
    timeUnit: TimeUnit = TimeUnit.MINUTES,
    connectionListener: ConnectionListener = ConnectionListener.NONE,
  ) : this(
    taskRunner = TaskRunner.INSTANCE,
    maxIdleConnections = maxIdleConnections,
    keepAliveDuration = keepAliveDuration,
    timeUnit = timeUnit,
    connectionListener = connectionListener,
  )

   */
  private val connections = ConcurrentLinkedQueue<RealConnection>()

  init {
    // Put a floor on the keep alive duration, otherwise cleanup will spin loop.
    require(keepAliveDuration > 0L) { "keepAliveDuration <= 0: $keepAliveDuration" }
  }

  fun idleConnectionCount(): Int =
    connections.count {
      it.withLock { it.calls.isEmpty() }
    }

  fun connectionCount(): Int = connections.size

  /**

    routePlanner: RoutePlanner? = null,
  ): RealConnectionPool =
    RealConnectionPool(
      taskRunner = taskRunner,
      maxIdleConnections = maxIdleConnections,
      keepAliveDuration = 100L,
      timeUnit = TimeUnit.NANOSECONDS,
      connectionListener = ConnectionListener.NONE,
      exchangeFinderFactory = { pool, address, user ->
        FastFallbackExchangeFinder(

    address. Use this to proactively open HTTP connections.

    Connections opened to fulfill this policy are subject to the connection pool's
    `keepAliveDuration` but do not count against the pool-wide `maxIdleConnections` limit.

    This feature increases the client's traffic and the load on the server. Talking to your server's
    operators before adopting it.