Blocking APIs may be inefficient because you hold a thread idle while waiting on the network. Threads are expensive because they have both a memory overhead and a context-switching overhead.

#### Framed protocols

    // Note: we don't process server frames so our client 'close' doesn't receive a server 'close'.
    assertThat(client.canceled).isFalse()

    taskFaker.advanceUntil(ns(4_999))
    assertThat(client.canceled).isFalse()

    taskFaker.advanceUntil(ns(5_000))
    assertThat(client.canceled).isTrue()

    client.processNextFrame() // This won't get a frame, but it will get a closed pipe.

  /**
   * HTTP/2 only. Send a push promise header block.
   *
   * A push promise contains all the headers that pertain to a server-initiated request, and a
   * `promisedStreamId` to which response frames will be delivered. Push promise frames are sent as
   * a part of the response to `streamId`. The `promisedStreamId` has a priority of one greater than
   * `streamId`.
   *
   * @param streamId client-initiated stream ID.  Must be an odd number.

1F4F9..1F4FC  ; valid                  ;      ; NV8    # 6.0  VIDEO CAMERA..VIDEOCASSETTE
1F4FD..1F4FE  ; valid                  ;      ; NV8    # 7.0  FILM PROJECTOR..PORTABLE STEREO
1F4FF         ; valid                  ;      ; NV8    # 8.0  PRAYER BEADS
1F500..1F53D  ; valid                  ;      ; NV8    # 6.0  TWISTED RIGHTWARDS ARROWS..DOWN-POINTING SMALL RED TRIANGLE

      assertThat(expected.message)
        .isEqualTo("Client-sent frames must be masked.")
    }
  }

  @Test fun serverSentFramesMustNotBeMasked() {
    data.write("8180".decodeHex())
    assertFailsWith<ProtocolException> {
      clientReader.processNextFrame()
    }.also { expected ->
      assertThat(expected.message)
        .isEqualTo("Server-sent frames must not be masked.")
    }
  }

```
$ adb shell setprop log.tag.okhttp.Http2 DEBUG
$ adb shell setprop log.tag.okhttp.TaskRunner DEBUG
$ adb logcat '*:E' 'okhttp.Http2:D' 'okhttp.TaskRunner:D'
```

### HTTP/2 Frame Logging

This logs inbound (`<<`) and outbound (`>>`) frames for HTTP/2 connections.

```
[2020-01-01 00:00:00] >> CONNECTION 505249202a20485454502f322e300d0a0d0a534d0d0a0d0a
[2020-01-01 00:00:00] >> 0x00000000     6 SETTINGS

  ): Boolean {
    // Don't send new frames after we've failed or enqueued a close frame.
    if (failed || enqueuedClose) return false

    // If this frame overflows the buffer, reject it and close the web socket.
    if (queueSize + data.size > MAX_QUEUE_SIZE) {
      close(CLOSE_CLIENT_GOING_AWAY, null)
      return false
    }

    // Enqueue the message frame.
    queueSize += data.size.toLong()

    close(ErrorCode.PROTOCOL_ERROR, ErrorCode.PROTOCOL_ERROR, e)
  }

  /**
   * Sends any initial frames and starts reading frames from the remote peer. This should be called
   * after [Builder.build] for all new connections.
   *
   * @param sendConnectionPreface true to send connection preface frames. This should always be true
   *     except for in tests that don't check for a connection preface.

    assertThat(webSocket.close(1000, null)).isFalse()
  }

  /**
   * There's no read timeout when reading the first byte of a new frame. But as soon as we start
   * reading a frame we enable the read timeout. In this test we have the server returning the first
   * byte of a frame but no more frames.
   */
  @Test
  fun readTimeoutAppliesWithinFrames() {
    webServer.dispatcher =
      object : Dispatcher() {

pkg p1, type I interface, Name() string
pkg p1, type I interface, PackageTwoMeth()
pkg p1, type I interface, Set(string, int64)
pkg p1, type I interface, unexported methods
pkg p1, type MyInt int
pkg p1, type Namer interface { Name }
pkg p1, type Namer interface, Name() string
pkg p1, type Private interface, X()
pkg p1, type Private interface, unexported methods
pkg p1, type Private //deprecated
pkg p1, type Public interface { X, Y }