val route = Route(address, proxy, inetSocketAddress)
        if (routeDatabase.shouldPostpone(route)) {
          postponedRoutes += route
        } else {
          routes += route
        }
      }

      if (routes.isNotEmpty()) {
        break
      }
    }

    if (routes.isEmpty()) {
      // We've exhausted all Proxies so fallback to the postponed routes.
      routes += postponedRoutes

  /** Returns a plan for the first attempt at [route]. This throws if no plan is possible. */
  @Throws(IOException::class)
  internal fun planConnectToRoute(
    route: Route,
    routes: List<Route>? = null,
  ): ConnectPlan {
    if (route.address.sslSocketFactory == null) {
      if (ConnectionSpec.CLEARTEXT !in route.address.connectionSpecs) {
        throw UnknownServiceException("CLEARTEXT communication not enabled for client")

    val selection = routeSelector.next()
    dns.assertRequests(uriHost)
    val routes = selection.routes
    assertRoute(routes[0], address, Proxy.NO_PROXY, dns.lookup(uriHost, 0), uriPort)
    assertRoute(routes[1], address, Proxy.NO_PROXY, dns.lookup(uriHost, 1), uriPort)
    assertThat(selection.next()).isSameAs(routes[0])
    assertThat(selection.next()).isSameAs(routes[1])
    assertThat(selection.hasNext()).isFalse()

In OkHttp some fields of the address come from the URL (scheme, hostname, port) and the rest come from the [OkHttpClient](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-ok-http-client/).

### [Routes](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-route/)

```Python hl_lines="35"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip "Tipp"
    Beachten Sie, dass Sie nicht den Router selbst (`invoices_callback_router`) an `callback=` übergeben, sondern das Attribut `.routes`, wie in `invoices_callback_router.routes`.

### Es in der Dokumentation ansehen

import okhttp3.Response
import okhttp3.Route

class RecordingOkAuthenticator(
  val credential: String?,
  val scheme: String?,
) : Authenticator {
  val responses = mutableListOf<Response>()
  val routes = mutableListOf<Route>()

  fun onlyResponse() = responses.single()

  fun onlyRoute() = routes.single()

  @Throws(IOException::class)
  override fun authenticate(
    route: Route?,
    response: Response,

{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip
    Notice that you are not passing the router itself (`invoices_callback_router`) to `callback=`, but the attribute `.routes`, as in `invoices_callback_router.routes`.

### Check the docs

Now you can start your app and go to <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

      pingIntervalMillis = pingIntervalMillis,
      retryOnConnectionFailure = retryOnConnectionFailure,
      user = user,
      routePlanner = routePlanner,
      route = route,
      routes = routes,
      attempt = attempt,
      tunnelRequest = tunnelRequest,
      connectionSpecIndex = connectionSpecIndex,
      isTlsFallback = isTlsFallback,
    )
  }

    http2Connection.start()
  }

  /**
   * Returns true if this connection can carry a stream allocation to `address`. If non-null
   * `route` is the resolved route for a connection.
   */
  internal fun isEligible(
    address: Address,
    routes: List<Route>?,
  ): Boolean {
    lock.assertHeld()

    // If this connection is not accepting new exchanges, we're done.

* `summary`: A short summary of the API.
* `description`: The description of your API, this can include markdown and will be shown in the docs.
* `routes`: A list of routes, these are each of the registered *path operations*. They are taken from `app.routes`.

!!! info
    The parameter `summary` is available in OpenAPI 3.1.0 and above, supported by FastAPI 0.99.0 and above.

## Overriding the defaults