This [sample factory](https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/PrintEvents.java) creates a unique ID for each call and uses that ID to differentiate calls in log messages.

    state = STATE_WRITING_REQUEST_BODY
    return ChunkedSink()
  }

  private fun newKnownLengthSink(): Sink {
    check(state == STATE_OPEN_REQUEST_BODY) { "state: $state" }
    state = STATE_WRITING_REQUEST_BODY
    return KnownLengthSink()
  }

  private fun newFixedLengthSource(length: Long): Source {
    check(state == STATE_OPEN_RESPONSE_BODY) { "state: $state" }
    state = STATE_READING_RESPONSE_BODY

  internal val plansToCancel = CopyOnWriteArrayList<RoutePlanner.Plan>()

  override fun timeout(): Timeout = timeout

  @SuppressWarnings("CloneDoesntCallSuperClone") // We are a final type & this saves clearing state.
  override fun clone(): Call = RealCall(client, originalRequest, forWebSocket)

  override fun request(): Request = originalRequest

  /**

import okio.BufferedSink
import okio.BufferedSource

/**
 * A connection to a remote web server capable of carrying 1 or more concurrent streams.
 *
 * Connections are shared in a connection pool. Accesses to the connection's state must be guarded
 * by holding a lock on the connection.
 */
class RealConnection(
  val taskRunner: TaskRunner,
  val connectionPool: RealConnectionPool,
  override val route: Route,
  /** The low-level TCP socket. */

_2020-04-06_

**This release fixes a severe bug where OkHttp incorrectly detected and recovered from unhealthy
connections.** Stale or canceled connections were incorrectly attempted when they shouldn't have
been, leading to rare cases of infinite retries. Please upgrade to this release!

 *  Fix: don't return stale DNS entries in `DnsOverHttps`. We were caching DNS results indefinitely

    package="okhttp.android.regression">
  <uses-permission android:name="android.permission.INTERNET" />

  <!-- For HttpEngine -->
  <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

#### Http2Connection

This lock guards internal state of each connection. This lock is never held for blocking operations. That means that we acquire the lock, read or write a few fields and release the lock. No I/O and no application-layer callbacks.

#### Http2Stream

  private val connectionUser: ConnectionUser,
  private val fastFallback: Boolean,
) {
  // State for negotiating the next proxy to use.
  private var proxies = emptyList<Proxy>()
  private var nextProxyIndex: Int = 0

  // State for negotiating the next socket address to use.
  private var inetSocketAddresses = emptyList<InetSocketAddress>()

  // State for negotiating failed routes
  private val postponedRoutes = mutableListOf<Route>()

    if (mockWebServer == null) throw new IllegalStateException();

    ByteString state = randomToken();
    synchronized (this) {
      listeners.put(state, listener);
    }

    return slackApi.authorizeUrl(scopes, redirectUrl(), state, team);
  }

  private ByteString randomToken() {
    byte[] bytes = new byte[16];
    secureRandom.nextBytes(bytes);

  }

  /**
   * When callers use `addEncodedQueryParameter()` we only encode what's strictly required. We
   * retain the encoded (or non-encoded) state of the input.
   */
  @Test
  fun queryCharactersNotReencodedWhenComposedWithAddEncoded() {
    val url =
      HttpUrl.Builder()
        .scheme("http")
        .host("host")