Concurrency
===========

This document describes the concurrency considerations for http/2 connections and the connection pool within OkHttp.

## HTTP/2 Connections

The HttpURLConnection API is a blocking API. You make a blocking write to send a request, and a blocking read to receive the response.

#### Blocking APIs

    util.concurrent tests under Guava.

    The problem is that GWT responds poorly to two .gwt.xml files in the same
    Java package; see
    https://groups.google.com/g/google-web-toolkit-contributors/c/CqYH59Dt_rQ/m/uVGW1QdUsXUJ
    for details.

    The summary is that it ignores one file in favor of the other.
    util.concurrent, like nearly all our packages, has two .gwt.xml files: one

import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;
import org.jspecify.annotations.Nullable;

/**
 * Unit test for {@link FakeTicker}.
 *
 * @author Jige Yu
 */
@GwtCompatible

import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;
import org.jspecify.annotations.Nullable;

/**
 * Unit test for {@link FakeTicker}.
 *
 * @author Jige Yu
 */
@GwtCompatible

 * the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Preconditions;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import java.util.ArrayDeque;
import java.util.ArrayList;

 * limitations under the License.
 */
package okhttp3

import java.util.ArrayDeque
import java.util.Deque
import java.util.concurrent.ExecutorService
import java.util.concurrent.SynchronousQueue
import java.util.concurrent.ThreadPoolExecutor
import java.util.concurrent.TimeUnit
import okhttp3.internal.assertLockNotHeld
import okhttp3.internal.connection.RealCall
import okhttp3.internal.connection.RealCall.AsyncCall

import com.google.common.util.concurrent.ListenableFuture;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import junit.framework.TestCase;
import org.jspecify.annotations.Nullable;

import com.google.common.util.concurrent.ListenableFuture;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import junit.framework.TestCase;
import org.jspecify.annotations.Nullable;

 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * MapMaker emulation.
 *
 * @author Charles Fry
 */
public final class MapMaker {
  private int initialCapacity = 16;

  public MapMaker() {}

     * Stored as a long value representing milliseconds since epoch.
     * Used for audit trail and concurrency control.
     */
    @ValidateTypeFailure
    public Long updatedTime;

    /**
     * The version number of the elevate word configuration for optimistic locking.
     * This field is required to prevent concurrent modification conflicts
     * by ensuring the configuration hasn't been modified by another process.
     */