{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[21:22] hl[21:22] *}

### Create a Session Dependency { #create-a-session-dependency }

A **`Session`** is what stores the **objects in memory** and keeps track of any changes needed in the data, then it **uses the `engine`** to communicate with the database.

        long deadline = System.currentTimeMillis() + 5000;  // 5 second timeout
        
        while (!rdmaConnection.canSend() && System.currentTimeMillis() < deadline) {
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
                throw new IOException("Interrupted waiting for send credit", e);
            }
        }

/// note | 技術詳細

`async` タスクは `await` に到達したときにのみキャンセルできます。`await` がない場合、ジェネレータ（`yield` を持つ関数）は適切にキャンセルできず、キャンセル要求後も実行が続く可能性があります。

この小さな例では `await` が不要なため、イベントループにキャンセルを処理する機会を与えるために `await anyio.sleep(0)` を追加しています。

これは大きなストリームや無限ストリームではさらに重要になります。

///

/// tip | 豆知識

`StreamingResponse` を直接返す代わりに、[データをストリームする](./stream-data.md) スタイルに従うことをおすすめします。こちらのほうがはるかに便利で、裏側でキャンセル処理も行ってくれます。

        assertEquals(2, result.length);
        assertEquals(" spaced value ", result[0]);
        assertEquals("\"  another  \"", result[1]);

        // Tab characters - quoted value keeps quotes
        value = "tab\tvalue,\"quoted\ttab\"";
        result = KuromojiCSVUtil.parse(value);
        assertEquals(2, result.length);
        assertEquals("tab\tvalue", result[0]);

   * (IOException) e.getCause()} throws a {@link ClassCastException} that discards the original
   * exception {@code e} if the cause is not an {@link IOException}, but {@code
   * Throwables.getCauseAs(e, IOException.class)} keeps {@code e} as the {@link
   * ClassCastException}'s cause.
   *
   * @throws ClassCastException if the cause cannot be cast to the expected type. The {@code
   *     ClassCastException}'s cause is {@code throwable}.

	bucketIdx := c.nextCleanupBucket
	timeToExpire := time.Until(c.buckets[bucketIdx].newestEntry)
	// wait for newest entry to expire before cleanup without holding lock
	if timeToExpire > 0 {
		c.mu.Unlock()
		time.Sleep(timeToExpire)
		c.mu.Lock()
	}
	for _, ent := range c.buckets[bucketIdx].entries {
		c.removeElement(ent)
	}
	c.nextCleanupBucket = (c.nextCleanupBucket + 1) % numBuckets
	c.mu.Unlock()
}

				return
			}

			h.config.LogOnceIf(
				context.Background(),
				fmt.Errorf("unable to send audit/log entry(s) to '%s' err '%w': %d", name, err, count),
				name,
			)

			time.Sleep(retryIntvl)
			if maxRetries == 0 {
				goto retry
			}
			retries++
			if retries <= maxRetries {
				goto retry
			}
		}

		entries = make([]any, 0)
		count = 0
		if !isDirQueue {

                }

                final long minSleep = retryInterval + retryCount * 1000L;
                final long maxSleep = retryInterval + retryCount * 2000L;
                ThreadUtil.sleep(RandomUtils.nextLong(minSleep, maxSleep));
                retryCount++;
            }
        }
    }

    /**
     * Destroys the client and closes connections.
     */
    @PreDestroy

    val request1ReceivedAt = System.currentTimeMillis()
    assertThat(server.takeRequest().headers["If-None-Match"]).isNull()

    // Hit that stored response. It's different, but Vary says it doesn't matter.
    Thread.sleep(10) // Make sure the timestamps are unique.
    val cacheHit =
      executeSynchronously(
        "/",
        "Accept-Language",
        "en-US",
        "Accept-Charset",
        "UTF-8",
      )

class _DefaultLifespan:
    """
    Default lifespan context manager that runs on_startup and on_shutdown handlers.

    This is a copy of the Starlette _DefaultLifespan class that was removed
    in Starlette. FastAPI keeps it to maintain backward compatibility with
    on_startup and on_shutdown event handlers.

    Ref: https://github.com/Kludex/starlette/pull/3117
    """

    def __init__(self, router: "APIRouter") -> None: