}
}

func (c *Connection) handlePing(ctx context.Context, m message) {
	var ping pingMsg
	if len(m.Payload) > 0 {
		_, err := ping.UnmarshalMsg(m.Payload)
		if err != nil {
			gridLogIf(ctx, err)
		}
	}
	// c.queueMsg will reuse m.Payload

	if m.MuxID == 0 {
		gridLogIf(ctx, c.queueMsg(m, &pongMsg{T: ping.T}))
		return
	}
	// Single calls do not support pinging.

      settings: Settings,
    )

    /** HTTP/2 only. */
    fun ackSettings()

    /**
     * Read a connection-level ping from the peer. `ack` indicates this is a reply. The data
     * in `payload1` and `payload2` opaque binary, and there are no rules on the content.
     */
    fun ping(
      ack: Boolean,
      payload1: Int,
      payload2: Int,
    )

    /**

      errorCode: ErrorCode,
    ) {
      check(type == -1)
      this.type = Http2.TYPE_RST_STREAM
      this.streamId = streamId
      this.errorCode = errorCode
    }

    override fun ping(
      ack: Boolean,
      payload1: Int,
      payload2: Int,
    ) {
      check(type == -1)
      type = Http2.TYPE_PING
      this.ack = ack
      this.payload1 = payload1

{* ../../docs_src/server_sent_events/tutorial005_py310.py hl[14] *}

## 技术细节 { #technical-details }

FastAPI 开箱即用地实现了一些 SSE 的最佳实践。

- 当 15 秒内没有任何消息时，发送一个**保活 `ping` 注释**，以防某些代理关闭连接，正如 [HTML 规范：Server-Sent Events](https://html.spec.whatwg.org/multipage/server-sent-events.html#authoring-notes) 中建议的那样。
- 设置 `Cache-Control: no-cache` 响应头，**防止缓存**流。

   * {@code Ping-From}</a> header field name.
   *
   * @since 19.0
   */
  public static final String PING_FROM = "Ping-From";

  /**
   * The HTTP <a href="http://html.spec.whatwg.org/multipage/semantics.html#hyperlink-auditing">
   * {@code Ping-To}</a> header field name.
   *
   * @since 19.0
   */
  public static final String PING_TO = "Ping-To";

  /**
   * The HTTP <a

	if m.outBlock == nil {
		// Closed
		return
	}
	select {
	case m.outBlock <- struct{}{}:
	default:
		gridLogIf(m.ctx, errors.New("output unblocked overflow"))
	}
}

func (m *muxServer) ping(seq uint32) pongMsg {
	if !m.checkSeq(seq) {
		msg := fmt.Sprintf("receive sequence number mismatch. want %d, got %d", m.RecvSeq, seq)
		return pongMsg{Err: &msg}
	}
	select {
	case <-m.ctx.Done():

{* ../../docs_src/server_sent_events/tutorial005_py310.py hl[14] *}

## 技術詳細 { #technical-details }

FastAPI は SSE のいくつかのベストプラクティスを標準で実装しています。

- メッセージがない場合は 15 秒ごとに「キープアライブ」用の `ping` コメントを送信し、一部のプロキシが接続を閉じるのを防ぎます（[HTML 仕様: Server-Sent Events](https://html.spec.whatwg.org/multipage/server-sent-events.html#authoring-notes) の推奨に従います）。
- ストリームの**キャッシュを防止**するため、`Cache-Control: no-cache` ヘッダーを設定します。

#### Do-stuff-later pool

Sometimes there's an action required like calling the application layer or responding to a ping, and the thread discovering the action is not the thread that should do the work. We enqueue a runnable on this executor and it gets handled by one of the executor's threads.

### Locks

    assertThat(sendPingFrame(true, expectedPayload1, expectedPayload2)).isEqualTo(frame)
    reader.nextFrame(
      requireSettings = false,
      object : BaseTestHandler() {
        override fun ping(
          ack: Boolean,
          payload1: Int,
          payload2: Int,
        ) {
          assertThat(ack).isTrue()
          assertThat(payload1).isEqualTo(expectedPayload1)

		ConnPool: db.ConnPool,
		Context:  context.Background(),
		Clauses:  map[string]clause.Clause{},
	}

	if err == nil && !config.DisableAutomaticPing {
		if pinger, ok := db.ConnPool.(interface{ Ping() error }); ok {
			err = pinger.Ping()
			if err != nil {
				if db, _ := db.DB(); db != nil {
					_ = db.Close()
				}
			}
		}
	}

	if err != nil {