*   attempt multiple proxy servers in sequence, eventually falling back to a direct
     *   connection.
     *
     * Set this to false to avoid retrying requests when doing so is destructive. In this case the
     * calling application should do its own recovery of connectivity failures.
     */
    fun retryOnConnectionFailure(retryOnConnectionFailure: Boolean) =
      apply {

    most common use of duplex calls is [gRPC][grpc_http2].

 *  New: Prevent OkHttp from retransmitting a request body by overriding `RequestBody.isOneShot()`.
    This is most useful when writing the request body is destructive.

 *  New: We've added `requestFailed()` and `responseFailed()` methods to `EventListener`. These
    are called instead of `requestBodyEnd()` and `responseBodyEnd()` in some failure situations.