8. 注意，*路径操作函数*使用的是普通函数，不是异步函数；

    与往常一样，在 FastAPI 中，可以按需组合普通函数与异步函数；

    如果不清楚何时使用异步函数或普通函数，请参阅**急不可待？**一节中对 <a href="https://fastapi.tiangolo.com/async/#in-a-hurry" target="_blank" class="internal-link">`async` 与 `await`</a> 的说明；

9. *路径操作函数*返回的不是数据类（虽然它可以返回数据类），而是返回内含数据的字典列表；

    FastAPI 使用（包含数据类的） `response_model` 参数转换响应。

把 `dataclasses` 与其它类型注解组合在一起，可以组成不同形式的复杂数据结构。

更多内容详见上述代码内的注释。

## 深入学习

        }

        public Model get() {
            if (!set) {
                synchronized (this) {
                    if (!set) {
                        try {
                            this.wait();
                        } catch (InterruptedException e) {
                            // Ignore
                        }
                    }
                }
            }
            return model;

				UserDefined:      userDefined,
			})
			if err != nil {
				errs[idx] = err
				return
			}
			objInfos[idx] = objInfo
		}(i, req)
	}
	wg.Wait()

	return objInfos, errs

      lock.lock();
      try {
        locked.countDown();
        finishLatch.await(1, MINUTES);
      } catch (InterruptedException e) {
        fail(e.toString());
      } finally {
        lock.unlock();
      }
    }

    void waitUntilHoldingLock() throws InterruptedException {
      locked.await(1, MINUTES);
    }

    void releaseLockAndFinish() throws InterruptedException {

      lock.lock();
      try {
        locked.countDown();
        finishLatch.await(1, MINUTES);
      } catch (InterruptedException e) {
        fail(e.toString());
      } finally {
        lock.unlock();
      }
    }

    void waitUntilHoldingLock() throws InterruptedException {
      locked.await(1, MINUTES);
    }

    void releaseLockAndFinish() throws InterruptedException {

        "R0.20, R0.10, R0.10, R0.10"); // #7 (cont.), note, this matches #5
  }

  public void testBurstyAndUpdate() {
    RateLimiter rateLimiter = RateLimiter.create(1.0, stopwatch);
    rateLimiter.acquire(1); // no wait
    rateLimiter.acquire(1); // R1.00, to repay previous

    rateLimiter.setRate(2.0); // update the rate!

    rateLimiter.acquire(1); // R1.00, to repay previous (the previous was under the old rate!)

        "R0.20, R0.10, R0.10, R0.10"); // #7 (cont.), note, this matches #5
  }

  public void testBurstyAndUpdate() {
    RateLimiter rateLimiter = RateLimiter.create(1.0, stopwatch);
    rateLimiter.acquire(1); // no wait
    rateLimiter.acquire(1); // R1.00, to repay previous

    rateLimiter.setRate(2.0); // update the rate!

    rateLimiter.acquire(1); // R1.00, to repay previous (the previous was under the old rate!)

	}

	var i int
	for toExpire := range expireCh {
		select {
		case <-ctx.Done():
			return
		default:
		}
		if i > 0 {
			if wait := globalBatchConfig.ExpirationWait(); wait > 0 {
				time.Sleep(wait)
			}
		}
		i++
		wk.Take()
		go func(toExpire []expireObjInfo) {
			defer wk.Give()

			toExpireAll := make([]ObjectInfo, 0, len(toExpire))

minio server --address 127.0.0.1:9004 "http://127.0.0.1:9003/tmp/multisiteb/data/disterasure/xl{1...4}" \
	"http://127.0.0.1:9004/tmp/multisiteb/data/disterasure/xl{5...8}" >/tmp/siteb_2.log 2>&1 &

# Wait to make sure all MinIO instances are up

export MC_HOST_sitea=http://minioadmin:minioadmin@127.0.0.1:9001
export MC_HOST_siteb=http://minioadmin:minioadmin@127.0.0.1:9004

./mc ready sitea
./mc ready siteb

}

// TryLockedOpenFile - tries a new write lock, functionality
// it is similar to LockedOpenFile with with syscall.LOCK_EX
// mode but along with syscall.LOCK_NB such that the function
// doesn't wait forever but instead returns if it cannot
// acquire a write lock.
func TryLockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
	return lockedOpenFile(path, flag, perm, syscall.F_SETLK)
}