* will prefer pooled connections. Only pooled HTTP/2 connections are used for such de-duplication.
 *
 * It is possible to cancel the finding process by canceling its call.
 *
 * Implementations of this interface are not thread-safe. Each instance is thread-confined to the
 * thread executing the call.
 */
interface RoutePlanner {
  val address: Address

  /** Follow-ups for failed plans and plans that lost a race. */

Actually, all (or most) of the web frameworks work in this same way.

You never call those functions directly. They are called by your framework (in this case, **FastAPI**).

    val request = Request(server.url("/a"))
    val call = client.newCall(request)
    call.enqueue(
      object : Callback {
        override fun onFailure(
          call: Call,
          e: IOException,
        ) {
          failureRef.set(true)
          latch.countDown()
        }

        override fun onResponse(
          call: Call,
          response: Response,
        ) {

   *
   * <p>If another call to {@link #get} or {@link #getUnchecked} is currently loading the value for
   * {@code key}, simply waits for that thread to finish and returns its loaded value. Note that
   * multiple threads can concurrently load values for distinct keys.
   *
   * <p>Caches loaded by a {@link CacheLoader} will call {@link CacheLoader#load} to load new values

    public int[] batchInsert(List<User> list, RequestOptionCall<BulkRequestBuilder> call) {
        return batchInsert(list, call, null);
    }

    public int[] batchInsert(List<User> list, RequestOptionCall<BulkRequestBuilder> call,
            RequestOptionCall<IndexRequestBuilder> entityCall) {
        return doBatchInsert(new BulkList<>(list, call, entityCall), null);
    }

    public int[] batchUpdate(List<User> list) {

      } else {
        null
      }
    }

    override fun secureConnectStart(call: Call) {
      // Register to capture "Produced ClientHello handshake message".
      currentThread = Thread.currentThread()
      logger.addHandler(loggerHandler)
    }

    override fun secureConnectEnd(
      call: Call,
      handshake: Handshake?,
    ) {
      logger.removeHandler(loggerHandler)
    }

    }
  }

  /**
   * Returns an unmodifiable <b>view</b> of the union of two sets. The returned set contains all
   * elements that are contained in either backing set. Iterating over the returned set iterates
   * first over all the elements of {@code set1}, then over each element of {@code set2}, in order,
   * that is not contained in {@code set1}.
   *

 * {@link UnsupportedOperationException} when they are not implemented. Most implementations should
 * support either all add operations or none of them, all removal operations or none of them, and if
 * and only if all of these are supported, the {@code setCount} methods as well.
 *
 * <p>A multiset uses {@link Object#equals} to determine whether two instances should be considered

OkHttp Coroutines
=================

Support for Kotlin clients using coroutines.

```kotlin
val call = client.newCall(request)

call.executeAsync().use { response ->
  withContext(Dispatchers.IO) {
    println(response.body?.string())
  }
}
```

This is implemented using `suspendCancellableCoroutine`
but uses the standard Dispatcher in OkHttp. This means
that by default Kotlin's Dispatchers are not used.

        final Call call = client.newCall(request);

        // Schedule a job to cancel the call in 1 second.
        executor.schedule(new Runnable() {
          @Override public void run() {
            System.out.printf("%.2f Canceling call.%n", (System.nanoTime() - startNanos) / 1e9f);
            call.cancel();
            System.out.printf("%.2f Canceled call.%n", (System.nanoTime() - startNanos) / 1e9f);