{* ../../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。

      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

	}
	if n != len(p) {
		err = io.ErrShortWrite
		b.closeWithErr(err)
	}
	return n, err
}

func (b *streamingBitrotWriter) Close() error {
	// Close the underlying writer.
	// This will also flush the ring buffer if used.
	err := b.iow.Close()

	// Wait for all data to be written before returning else it causes race conditions.
	// Race condition is because of io.PipeWriter implementation. i.e consider the following

	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():

   * {@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

{* ../../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。

        String field = settings.array().get(SuggestSettings.DefaultKeys.SUPPORTED_FIELDS)[0];

        Map<String, Object> document = new HashMap<>();
        document.put(field, "Sing the Supercalifragilisticexpialidocious for Honorificabilitudinitatibus");
        suggester.indexer().indexFromDocument(new Map[] { document });
        suggester.refresh();

#### 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)

        def projectDir = 'C:\\some\\agent\\workspace'

        expect: