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

address may also share the same underlying TCP socket connection. Sharing a connection has substantial performance benefits: lower latency, higher throughput (due to [TCP slow start](https://www.igvita.com/2011/10/20/faster-web-vs-tcp-slow-start/)) and conserved battery. OkHttp uses a [ConnectionPool](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-connection-pool/) that automatically reuses HTTP/1.x connections and multiplexes HTTP/2 connections.

In OkHttp some fields of the address come...

      }
    }
    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.

    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,
  ) {}

  /**

            }
            connection.setRequestProperty(key, value.toString());
        }
        connection.setAllowUserInteraction(allowUserInteraction);
        connection.setDoInput(doInput);
        connection.setDoOutput(doOutput);
        connection.setIfModifiedSince(ifModifiedSince);
        connection.setUseCaches(useCaches);
    }

 * **ExchangeFinder** chooses which connection carries each exchange. Where possible it will use the same connection for all exchanges in a single call. It prefers reusing pooled connections over establishing new connections.      

#### Per-Connection Locks

    /**
     * Get transport connection
     * 
     * @param tc
     *            context to use
     * @param address
     * @param port
     * @param exclusive
     *            whether to acquire an unshared connection
     * @param forceSigning
     *            whether to enforce SMB signing on this connection
     * @return a transport connection to the target
     */

    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()

 *
 *  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.
 *