printEvent("callStart");
  }

  @Override public void callEnd(Call call) {
    printEvent("callEnd");
  }

  ...
}
```

We can use this listener to race a pair of concurrent HTTP requests:

```java
Request washingtonPostRequest = new Request.Builder()
    .url("https://www.washingtonpost.com/")
    .build();
client.newCall(washingtonPostRequest).enqueue(new Callback() {
  ...

 */
@file:Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")

package okhttp3.logging

import java.io.IOException
import java.nio.charset.Charset
import java.util.TreeSet
import java.util.concurrent.TimeUnit
import okhttp3.Headers
import okhttp3.HttpUrl
import okhttp3.Interceptor
import okhttp3.OkHttpClient
import okhttp3.Response
import okhttp3.internal.charsetOrUtf8
import okhttp3.internal.http.promisesBody

import assertk.assertions.isEqualTo
import assertk.assertions.isTrue
import java.io.IOException
import java.io.InputStreamReader
import java.io.Reader
import java.nio.charset.StandardCharsets
import java.util.concurrent.atomic.AtomicBoolean
import kotlin.test.assertFailsWith
import okhttp3.MediaType.Companion.toMediaType
import okhttp3.ResponseBody.Companion.toResponseBody
import okhttp3.internal.and
import okio.Buffer

 *  Fix: Immediately update the connection's flow control window instead of waiting for the
    receiving stream to process it.

    This change may increase OkHttp's memory use for applications that make many concurrent HTTP
    calls and that can receive data faster than they can process it. Previously, OkHttp limited
    HTTP/2 to 16 MiB of unacknowledged data per connection. With this fix there is a limit of 16 MiB

import assertk.assertions.matches
import java.math.BigInteger
import java.security.KeyFactory
import java.security.spec.PKCS8EncodedKeySpec
import java.security.spec.X509EncodedKeySpec
import java.util.concurrent.TimeUnit
import okhttp3.testing.PlatformRule
import okhttp3.tls.HeldCertificate.Companion.decode
import okio.ByteString.Companion.decodeBase64
import org.bouncycastle.asn1.x509.GeneralName

import java.net.HttpURLConnection
import java.net.URL
import java.nio.ByteBuffer
import java.util.concurrent.CompletableFuture
import java.util.concurrent.ExecutionException
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors
import java.util.concurrent.TimeUnit
import kotlin.coroutines.cancellation.CancellationException
import okio.Buffer
import org.junit.After

 * limitations under the License.
 */
package okhttp3.internal.connection

import java.io.IOException
import java.util.concurrent.CopyOnWriteArrayList
import java.util.concurrent.LinkedBlockingDeque
import java.util.concurrent.TimeUnit
import okhttp3.internal.concurrent.Task
import okhttp3.internal.concurrent.TaskRunner
import okhttp3.internal.connection.RoutePlanner.ConnectResult
import okhttp3.internal.connection.RoutePlanner.Plan

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package okhttp3.internal.concurrent

import java.util.concurrent.CountDownLatch
import java.util.concurrent.RejectedExecutionException
import java.util.concurrent.locks.ReentrantLock
import kotlin.concurrent.withLock
import okhttp3.internal.assertNotHeld
import okhttp3.internal.okHttpName

/**

 * limitations under the License.
 */
package okhttp3.internal.concurrent

import java.util.concurrent.BlockingQueue
import java.util.concurrent.SynchronousQueue
import java.util.concurrent.ThreadFactory
import java.util.concurrent.ThreadPoolExecutor
import java.util.concurrent.TimeUnit
import java.util.concurrent.locks.Condition
import java.util.concurrent.locks.ReentrantLock
import java.util.logging.Logger

okhttp3.internal.authenticator.JavaNetAuthenticatorTest
okhttp3.internal.cache.DiskLruCacheTest
okhttp3.internal.cache2.FileOperatorTest
okhttp3.internal.cache2.RelayTest
okhttp3.internal.concurrent.TaskLoggerTest
okhttp3.internal.concurrent.TaskRunnerRealBackendTest
okhttp3.internal.concurrent.TaskRunnerTest
okhttp3.internal.connection.ConnectionPoolTest
okhttp3.internal.connection.ConnectionSpecSelectorTest
okhttp3.internal.connection.RouteExceptionTest