// operations, such as bitrot verification or data usage scanning.
// Every 10 seconds a space character is sent.
// keepHTTPReqResponseAlive will wait for the returned body to be read before starting the ticker.
// The returned function should always be called to release resources.
// An optional error can be sent which will be picked as text only error,
// without its original type by the receiver.

   * </pre>
   *
   * @param throwable the non-null {@code Throwable} to extract causes from
   * @return an unmodifiable list containing the cause chain starting with {@code throwable}
   * @throws IllegalArgumentException if there is a loop in the causal chain
   */
  public static List<Throwable> getCausalChain(Throwable throwable) {
    checkNotNull(throwable);

import java.util.TreeSet;
import org.jspecify.annotations.Nullable;

/**
 * An immutable builder for {@link Multimap} instances, letting you independently select the desired
 * behaviors (for example, ordering) of the backing map and value-collections. Example:
 *
 * {@snippet :
 * ListMultimap<UserId, ErrorResponse> errorsByUser =
 *     MultimapBuilder.linkedHashKeys().arrayListValues().build();

import java.util.TreeSet;
import org.jspecify.annotations.Nullable;

/**
 * An immutable builder for {@link Multimap} instances, letting you independently select the desired
 * behaviors (for example, ordering) of the backing map and value-collections. Example:
 *
 * {@snippet :
 * ListMultimap<UserId, ErrorResponse> errorsByUser =
 *     MultimapBuilder.linkedHashKeys().arrayListValues().build();

    assertThat(request.tag(String::class.java)).isSameInstanceAs(stringTag)
    assertThat(request.tag(Long::class.javaObjectType)).isSameInstanceAs(longTag)
  }

  /** Confirm that we don't accidentally share the backing map between objects. */
  @Test
  fun tagsAreImmutable() {
    val builder =
      Request
        .Builder()
        .url("https://square.com")
    val requestA = builder.tag(String::class.java, "a").build()

    private final AtomicLong lastFailureTime = new AtomicLong(0);
    private final AtomicLong lastStateChangeTime = new AtomicLong(System.currentTimeMillis());

    // Metrics tracking
    private final AtomicLong totalRequests = new AtomicLong(0);
    private final AtomicLong totalFailures = new AtomicLong(0);
    private final AtomicLong totalSuccesses = new AtomicLong(0);

     */
    protected final Object inLock = new Object();
    /**
     * Lock object for synchronizing output operations
     */
    protected final Object outLock = new Object();

    /**
     * Map for tracking pending responses by their key
     */
    protected final Map<Long, Response> response_map = new ConcurrentHashMap<>(10);
    private final AtomicLong usageCount = new AtomicLong(1);

    /**

   *     static
   */
  private void testParameter(
      @Nullable Object instance, Invokable<?, ?> invokable, int paramIndex, Class<?> testedClass) {
    /*
     * com.google.common is starting to rely on type-use annotations, which aren't visible under
     * Android VMs and in open-source guava-android. So we skip testing there.
     */
    if (Reflection.getPackageName(testedClass).startsWith("com.google.common")) {

 * These always reflect the latest state of the multimap itself. When they support modification, the
 * changes are <i>write-through</i> (they automatically update the backing multimap). These view
 * collections are:
 *
 * <ul>
 *   <li>{@link #asMap}, mentioned above
 *   <li>{@link #keys}, {@link #keySet}, {@link #values}, {@link #entries}, which are similar to the

/// tip

先別擔心這裡提到的「容器」、Docker 或 Kubernetes 如果現在還不太懂。

我會在未來的章節進一步說明容器映像、Docker、Kubernetes 等等：[容器中的 FastAPI - Docker](docker.md)。

///

## 啟動前的前置步驟 { #previous-steps-before-starting }

很多情況下，你會希望在應用「啟動之前」先執行一些步驟。

例如，你可能想先執行「資料庫遷移」。

但在多數情況下，你會希望這些步驟只執行「一次」。

所以，你會希望用「單一行程」來執行那些「前置步驟」，在啟動應用之前完成。