func gridLogOnceIf(ctx context.Context, err error, id string, errKind ...interface{}) {
	logger.LogOnceIf(ctx, "grid", err, id, errKind...)
}

// A Connection is a remote connection.
// There is no distinction externally whether the connection was initiated from
// this server or from the remote.
type Connection struct {
	// NextID is the next ID that can be used (atomic).
	NextID uint64

	// LastPong is last pong time (atomic)

 */
interface Connection {
  /** Returns the route used by this connection. */
  fun route(): Route

  /**
   * Returns the socket that this connection is using. Returns an
   * [SSL socket][javax.net.ssl.SSLSocket] if this connection is HTTPS. If this is an HTTP/2
   * connection the socket may be shared by multiple concurrent calls.
   */
  fun socket(): Socket

      }
    }
    return null
  }

  fun put(connection: RealConnection) {
    connection.lock.assertHeld()

    connections.add(connection)
//    connection.queueEvent { connectionListener.connectEnd(connection) }
    scheduleCloser()
  }

  /**
   * Notify this pool that [connection] has become idle. Returns true if the connection has been
   * removed from the pool and should be closed.

 *
 *  4. If there's no existing connection, make a list of routes (which may require blocking DNS
 *     lookups) and attempt a new connection them. When failures occur, retries iterate the list of
 *     available routes.
 *
 * If the pool gains an eligible connection while DNS, TCP, or TLS work is in flight, this finder
 * will prefer pooled connections. Only pooled HTTP/2 connections are used for such de-duplication.
 *

    lock.assertNotHeld()

    val connection = this.connection
    if (connection != null) {
      connection.lock.assertNotHeld()
      val toClose: Socket? =
        connection.withLock {
          // Sets this.connection to null.
          releaseConnectionNoEvents()
        }
      if (this.connection == null) {
        toClose?.closeQuietly()

    if (pooled3 != null) return pooled3.connection

    connection.withLock {
      connectionPool.put(connection)
      user.acquireConnectionNoEvents(connection)
    }

    user.connectionAcquired(connection)
    user.connectionConnectionAcquired(connection)
    return connection
  }

  override fun trackFailure(
    call: RealCall,
    e: IOException?,

    connection: Connection,
    route: Route,
    call: Call,
  ) {}

  /**
   * Invoked when a connection is released as no longer required.
   */
  open fun connectionClosed(connection: Connection) {}

  /**
   * Invoked when a call is assigned a particular connection.
   */
  open fun connectionAcquired(
    connection: Connection,
    call: Call,
  ) {}

  /**

  }

  /**
   * Return the route from [connection] if it should be retried, even if the connection itself is
   * unhealthy. The biggest gotcha here is that we shouldn't reuse routes from coalesced
   * connections.
   */
  private fun retryRoute(connection: RealConnection): Route? {
    return connection.withLock {
      when {
        connection.routeFailureCount != 0 -> null

      assertThat(result0).isEqualTo(plan1.connection)
    }

    taskFaker.runTasks()
    assertEvents(
      "take plan 0",
      "plan 0 TCP connecting...",
      "plan 0 TCP connected",
      "plan 0 TLS connecting...",
      "plan 0 needs follow-up",
      "plan 1 TCP connecting...",
      "plan 1 TCP connected",
      "plan 1 TLS connecting...",
      "plan 1 TLS connected",
    )

_2020-03-08_

 *  Fix: Don't reuse a connection on redirect if certs match but DNS does not. For better
    locality and performance OkHttp attempts to use the same pooled connection across redirects and
    follow-ups. It independently shares connections when the IP addresses and certificates match,
    even if the host names do not. In 4.4.0 we introduced a regression where we shared a connection