*
   * <p>The corresponding root-mean-square error in {@code x} as a function of {@code y} is a
   * fraction {@code sqrt(1/(R*R) - 1)} of the population standard deviation of {@code x}. This fit
   * does not normally minimize that error: to do that, you should swap the roles of {@code x} and
   * {@code y}.
   *
   * <h3>Non-finite values</h3>
   *

Dies wurde in Version 0.110.0 geändert, um unbehandelten Speicherverbrauch durch weitergeleitete Exceptions ohne Handler (interne Serverfehler) zu beheben und um es mit dem Verhalten von normalem Python-Code konsistent zu machen.

### Hintergrundtasks und Abhängigkeiten mit `yield`, Technische Details { #background-tasks-and-dependencies-with-yield-technical-details }

Sie können `async def` oder einfach `def` verwenden.

Und Sie können Abhängigkeiten mit `async def` innerhalb normaler `def`-*Pfadoperation-Funktionen* oder `def`-Abhängigkeiten innerhalb von `async def`-*Pfadoperation-Funktionen*, usw. deklarieren.

Es spielt keine Rolle. **FastAPI** weiß, was zu tun ist.

/// note | Hinweis

Bu fonksiyonlar (class'ları doğrudan kullanmak yerine) editörünüzün type'larıyla ilgili hata işaretlememesi için vardır.

Bu sayede, bu hataları yok saymak üzere özel ayarlar eklemeden normal editörünüzü ve coding araçlarınızı kullanabilirsiniz.

    public void tearDown() {
        if (rateLimiter != null) {
            rateLimiter.close();
        }
    }

    @Test
    public void testNormalAuthentication() throws Exception {
        // Normal authentication should be allowed
        assertTrue(rateLimiter.checkAttempt("user1", "192.168.1.1"), "First attempt should be allowed");

        // Record success
        rateLimiter.recordSuccess("user1", "192.168.1.1");

你的 API 的使用者（外部開發者）會透過一個 POST 請求在你的 API 中建立一張發票。

然後你的 API 會（讓我們想像）：

* 將發票寄給該外部開發者的某位客戶。
* 代收款項。
* 再把通知回傳給 API 使用者（外部開發者）。
    * 這會透過從「你的 API」向該外部開發者提供的「外部 API」送出 POST 請求完成（這就是「回呼」）。

## 一般的 **FastAPI** 應用 { #the-normal-fastapi-app }

先看看在加入回呼之前，一個一般的 API 應用會長什麼樣子。

它會有一個接收 `Invoice` body 的「路徑操作」，以及一個查詢參數 `callback_url`，其中包含用於回呼的 URL。

這部分很正常，多數程式碼你應該已經很熟悉了：

        String configPath = form.crawlingConfigPath.trim();
        if (StringUtil.isBlank(configName)) {
            configName = StringUtils.abbreviate(configPath, 30);
        }

        // normalize
        final StringBuilder buf = new StringBuilder(1000);
        for (int i = 0; i < configPath.length(); i++) {
            final char c = configPath.charAt(i);
            if (c == '\\') {

part of the Derivative Works; within the Source form or documentation, if 
provided along with the Derivative Works; or, within a display generated by 
the Derivative Works, if and wherever such third-party notices normally 
appear. The contents of the NOTICE file are for informational purposes only 
and do not modify the License. You may add Your own attribution notices 
within Derivative Works that You distribute, alongside or as an addendum to 

            File currentPom = project.getFile();
            if (currentPom != null) {
                MavenSession session = event.getSession();
                Path current = currentPom.toPath().toAbsolutePath().normalize();
                Path topDirectory = session.getTopDirectory();
                if (topDirectory != null && current.startsWith(topDirectory)) {
                    current = topDirectory.relativize(current);

public class SimpleCircuitBreaker {

    private static final Logger log = LoggerFactory.getLogger(SimpleCircuitBreaker.class);

    /**
     * Circuit breaker states
     */
    public enum State {
        CLOSED, // Normal operation
        OPEN, // Failing, requests blocked
        HALF_OPEN // Testing recovery
    }

    private final String name;
    private final AtomicReference<State> state = new AtomicReference<>(State.CLOSED);