return null
        }
        val priorResponse = userResponse.priorResponse
        if (priorResponse != null && priorResponse.code == HTTP_CLIENT_TIMEOUT) {
          // We attempted to retry and got another timeout. Give up.
          return null
        }

        if (retryAfter(userResponse, 0) > 0) {
          return null
        }

        return userResponse.request
      }

With fast fallback, OkHttp attempts to connect to multiple web servers concurrently. It keeps whichever route connects first and cancels all of the others. Its rules are:

 * Prefer to alternate IP addresses from different address families, (IPv6 / IPv4), starting with IPv6.
 * Don't start a new attempt until 250 ms after the most recent attempt was started.

A single HTTP call may require follow-up requests to be made to handle authentication challenges, redirects, and HTTP-layer timeouts. In such cases multiple connections, requests, and responses may be attempted. Follow-ups are another reason a single call may trigger multiple events of the same type.

    ```kotlin
    if (credential == response.request.header("Authorization")) {
      return null // If we already failed with these credentials, don't retry.
     }
    ```

    You may also skip the retry when you’ve hit an application-defined attempt limit:

    ```kotlin
    if (response.responseCount >= 3) {

   * proxy server can issue an auth challenge and then close the connection.
   *
   * @return the next plan to attempt, or null if no further attempt should be made either because
   *     we've successfully connected or because no further attempts should be made.
   */
  @Throws(IOException::class)
  internal fun connectTunnel(): ConnectResult {
    val nextTunnelRequest =
      createTunnel()

  timeout: Int,
  timeUnit: TimeUnit,
): Boolean =
  try {
    this.skipAll(timeout, timeUnit)
  } catch (_: IOException) {
    false
  }

/**
 * Returns true if new reads and writes should be attempted on this.
 *
 * Unfortunately Java's networking APIs don't offer a good health check, so we go on our own by
 * attempting to read with a short timeout. If the fails immediately we know the socket is
 * unhealthy.
 *

      socket.close()
      openClientSockets.remove(socket.javaNetSocket)
    }

    /**
     * Respond to `CONNECT` requests until a non-tunnel response is peeked. Returns true if further
     * calls should be attempted on the socket.
     */
    @Throws(IOException::class, InterruptedException::class)
    private fun processTunnelRequests(): Boolean {
      if (!dispatcher.peek().inTunnel) return true // No tunnel requests.

    /**
     * Sets the authenticator used to respond to challenges from origin servers. Use
     * [proxyAuthenticator] to set the authenticator for proxy servers.
     *
     * If unset, the [no authentication will be attempted][Authenticator.NONE].
     */
    fun authenticator(authenticator: Authenticator) =
      apply {
        this.authenticator = authenticator
      }

        } catch (NullPointerException e) {
            // Expected due to null user - depth check passed, processing attempted
            assertTrue(true);
        } catch (Exception e) {
            // Other exceptions are also acceptable as we're testing depth logic
            assertTrue(true);
        }
    }

    @Test
    public void test_processParentGroup_callsOverloadWithDepth() {

/**
 * An unbounded {@linkplain BlockingQueue blocking queue} that uses the same ordering rules as class
 * {@link PriorityQueue} and supplies blocking retrieval operations. While this queue is logically
 * unbounded, attempted additions may fail due to resource exhaustion (causing {@code
 * OutOfMemoryError}). This class does not permit {@code null} elements. A priority queue relying on