* or both.
 *
 * ## Authentication Retries
 *
 * If your authentication may be flaky and requires retries you should apply some policy
 * to limit the retries by the class of errors and number of attempts.  To get the number of
 * attempts to the current point use this function.
 *
 * ```java
 * private int responseCount(Response response) {
 *   int result = 1;
 *   while ((response = response.priorResponse()) != null) {

     * Connections will still be closed if they idle beyond the keep-alive but will be replaced.
     */
    @JvmField val minimumConcurrentCalls: Int = 0,
    /** How long to wait to retry pre-emptive connection attempts that fail. */
    @JvmField val backoffDelayMillis: Long = 60 * 1000,
    /** How much jitter to introduce in connection retry backoff delays */
    @JvmField val backoffJitterMillis: Int = 100,
  )

    of unacknowledged data per stream and no per-connection limit.

 *  Fix: Don't operate on a connection after it's been returned to the pool. This race occurred
    on failed web socket connection attempts.

 *  Upgrade: [Okio 3.6.0][okio_3_6_0].

 *  Upgrade: [Kotlin 1.8.21][kotlin_1_8_21].


## Version 4.11.0

_2023-04-22_

    makeSimpleCall()
  }

  /**
   * If the server returns a full response, it doesn't really matter if the HTTP/2 stream is reset.
   * Attempts to write the request body fails fast.
   */
  @Test
  fun serverTruncatesRequestHttp2OnDuplexRequest() {
    enableProtocol(Protocol.HTTP_2)

    server.enqueue(
      MockResponse(
        body = "abc",

   * 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()

    )

    val call = client.newCall(Request(url))
    val response = call.execute()
    assertThat(response.body.string()).isEqualTo("hello from IPv6")

    // In the process we made two connection attempts including one failure.
    assertThat(listener.recordedEventTypes().filter { it == "ConnectStart" }).hasSize(1)
    assertThat(listener.recordedEventTypes().filter { it == "ConnectEnd" }).hasSize(1)

 *
 *  3. Attempt plans from prior connect attempts for this call. These occur as either follow-ups to
 *     failed connect attempts (such as trying the next [ConnectionSpec]), or as attempts that lost
 *     a race in fast follow-up.
 *
 *  4. If there's no existing connection, make a list of routes (which may require blocking DNS

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.

import okhttp3.internal.okHttpName

/**
 * Speculatively connects to each IP address of a target address, returning as soon as one of them
 * connects successfully. This kicks off new attempts every 250 ms until a connect succeeds.
 */
internal class FastFallbackExchangeFinder(
  override val routePlanner: RoutePlanner,
  private val taskRunner: TaskRunner,
) : ExchangeFinder {

 * MockWebServer. In cases where logic is particularly tricky, we use unit tests. This class makes
 * it easy to get sample values to use in such tests.
 *
 * This class is pretty fast and loose with default values: it attempts to provide values that are
 * well-formed, but doesn't guarantee values are internally consistent. Callers must take care to
 * configure the factory when sample values impact the correctness of the test.
 */